Core stability

Department of Public and Occupational HealthEMGO+ Institute for Health and Care ResearchVU University Medical Center, Amsterdam, the Netherlands

Evert Verhagen

CORE STABILITYMYTH OR REALITY?

vrijdag 23 augustus 13


Evert Verhagen







EMGO+ INSTITUTEFOR HEALTH AND CARE RESEARCH

• Interfaculty research institute of the VU University Amsterdam and VU University Medical Center Amsterdam

• Activities deal with research in primary care and public health, focusing on chronic diseases and aging

• Public Health is binding factor of studies ..."the science and art of preventing disease, prolonging life and promoting health through the organized efforts and informed choices of society, organizations, public and private, communities and individuals."


TWO DIMENSIONSPopulationLaboratory

EffectivenessEffic

acy

Optimal effect for society or individual


TWO DIMENSIONSPopulationLaboratory

90% efficacious10% effective




CORE STABILITYFOR THE PUBLIC

• Core stability relates to the bodily region bounded by the abdominal wall, the pelvis, the lower back and the diaphragm and its ability to stabilise the body during movementSource: wikipedia


http://en.wikipedia.org/wiki/Abdominal_wall

http://en.wikipedia.org/wiki/Abdominal_wall

http://en.wikipedia.org/wiki/Pelvis

http://en.wikipedia.org/wiki/Pelvis

http://en.wikipedia.org/wiki/Lower_back

http://en.wikipedia.org/wiki/Lower_back

http://en.wikipedia.org/wiki/Thoracic_diaphragm

http://en.wikipedia.org/wiki/Thoracic_diaphragm





PARALLELS WITH STRETCHING

• Stretching has become embedded in sport folklore as the universal strategy for injury preventionThacker et al. MSSE 2004


PARALLELS WITH STRETCHING

• Ongoing debate on the beneficial and detrimental effects of stretching on ...

performance

injury risk

therapeutic outcomes


1. Identifyburden ofdisease 2. Define

theoriesfor causation

3. Establishefficacy

4. Establisheffectiveness

5. Communityeffectiveness,economicimplications

6. Implemen-tation

7. Programevaluation

Tugwell et al. J Chronic Dis 1985


1 biomechanical, physical and neurophysiological changes

2epidemiological

(cost)effectiveness evidence leading to clinical / practical

guidelines

3practical & public health

impact through high compliance and proper use of

effective measures



2epidemiological


guidelines



effective measures



• Theoretical conceptWhat is CS?

• Conceptual definitionHow do we define CS?

• Operational definitionWhich muscles and movements adjoin to CS?

• MeasurementsValid?Reliable?Responsive?

• Most of these ...

Ill described

No consensus

Contradicting results

2epidemiological


guidelines



effective measures



2epidemiological


guidelines



effective measures






Ill described

No consensus




2epidemiological


guidelines



effective measures






Ill described

No consensus



• Bottom up approach

• Learn from practical and clinical outcomes

What works in practice?

Can we measure that?

What if we repeat practical approaches in controlled settings?


2epidemiological


guidelines



effective measures


Optimizing Performance by ImprovingCore Stability and Core StrengthAngela E. Hibbs,1,3 Kevin G. Thompson,1,4 Duncan French,1 Allan Wrigley 2 and Iain Spears3

1 English Institute of Sport, Gateshead, UK2 Canadian Sport Centre Pacific, Vancouver, British Columbia, Canada3 University of Teesside, Middlesbrough, UK4 School of Psychology and Sports Science, Northumbria University, Newcastle, UK

ContentsAbstract. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9951. Definition of Performance, Core Stability and Core Strength . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9962. Functional Anatomy of the ‘Core’ as it Relates to Athletic Performance . . . . . . . . . . . . . . . . . . . . . . . 9973. Types of Core Training . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9984. Evidence of Core Training Benefits. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1000

4.1 Rehabilitation Sector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10014.2 Athletic Sector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1002

5. Measuring the Core and its Relation to Performance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10046. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1006

Abstract Core stability and core strength have been subject to research since theearly 1980s. Research has highlighted benefits of training these processes forpeople with back pain and for carrying out everyday activities. However, lessresearch has been performed on the benefits of core training for elite athletesand how this training should be carried out to optimize sporting perfor-mance. Many elite athletes undertake core stability and core strength trainingas part of their training programme, despite contradictory findings andconclusions as to their efficacy. This is mainly due to the lack of a goldstandard method for measuring core stability and strength when performingeveryday tasks and sporting movements. A further confounding factor is thatbecause of the differing demands on the core musculature during everydayactivities (low load, slow movements) and sporting activities (high load,resisted, dynamic movements), research performed in the rehabilitation sec-tor cannot be applied to the sporting environment and, subsequently, dataregarding core training programmes and their effectiveness on sportingperformance are lacking.

There are many articles in the literature that promote core training pro-grammes and exercises for performance enhancement without providing astrong scientific rationale of their effectiveness, especially in the sportingsector. In the rehabilitation sector, improvements in lower back injurieshave been reported by improving core stability. Few studies have observedany performance enhancement in sporting activities despite observing

REVIEWARTICLESports Med 2008; 38 (12): 995-10080112-1642/08/0012-0995/$48.00/0

ª 2008 Adis Data Information BV. All rights reserved.CS TO IMPROVE SPORTS PERFORMANCE

• There are many articles in the literature that promote core training for performance enhancement without providing a strong scientific rationale of their effectiveness

• Evidence of core training benefits?

Hibbs et al. 2012


CORE TRAINING AND POTENTIAL PERFORMANCE BENEFITS

definitions valid and reliable measuresClinical core stability tests are not reliableICCs did not exceed 0.40Weir et al. CJSM 2010

Hibbs et al. 2012


WHAT DOES THE LITERATURE SAY?

• Improvements in core stability and core strength following a core training program

• Ambiguous results on performance enhancement in sporting activities

Indirect impact on sporting performance by allowing athletes to train injury free more often?

Hibbs et al. 2012


RELATIONSHIP BETWEEN CORE STABILITY,FUNCTIONAL MOVEMENT, AND PERFORMANCE

TOMOKO OKADA, KELLIE C. HUXEL, AND THOMAS W. NESSER

Exercise Physiology Laboratory, Athletic Training Department, Indiana State University, Terre Haute, Indiana

ABSTRACT

Okada, T, Huxel, KC, and Nesser, TW. Relationship between

core stability, functional movement, and performance.

J Strength Cond Res 25(1): 252–261, 2011—The purpose

of this study was to determine the relationship between core

stability, functional movement, and performance. Twenty-eight

healthy individuals (age = 24.4 6 3.9 yr, height = 168.8 6 12.5

cm, mass = 70.2 6 14.9 kg) performed several tests in 3

categories: core stability (flexion [FLEX], extension [EXT], right

and left lateral [LATr/LATl]), functional movement screen (FMS)

(deep squat [DS], trunk-stability push-up [PU], right and left

hurdle step [HSr/HSl], in-line lunge [ILLr/ILLl], shoulder mobility

[SMr/SMl], active straight leg raise [ASLRr/ASLRl], and rotary

stability [RSr/RSl]), and performance tests (backward medicine

ball throw [BOMB], T-run [TR], and single leg squat [SLS]).

Statistical significance was set at p # 0.05. There were

significant correlations between SLS and FLEX (r = 0.500),

LATr (r = 0.495), and LATl (r = 0.498). The TR correlated

significantly with both LATr (r = 0.383) and LATl (r = 0.448).

Of the FMS, BOMB was significantly correlated with HSr (r =

0.415), SMr (r = 0.388), PU (r = 0.407), and RSr (r = 0.391).

The TR was significantly related with HSr (r = 0.518), ILLl

(r = 0.462) and SMr (r = 0.392). The SLS only correlated

significantly with SMr (r = 0.446). There were no significant

correlations between core stability and FMS. Moderate to weak

correlations identified suggest core stability and FMS are not

strong predictors of performance. In addition, existent assess-

ments do not satisfactorily confirm the importance of core stability

on functional movement. Despite the emphasis fitness profes-

sionals have placed on functional movement and core training for

increased performance, our results suggest otherwise. Although

training for core and functional movement are important to include

in a fitness program, especially for injury prevention, they should

not be the primary emphasis of any training program.

KEY WORDS power, agility, muscle endurance

INTRODUCTION

Core stability is achieved through stabilization ofone’s torso, thus allowing optimal production,transfer, and control of force and motion to theterminal segment during an integrated kinetic

chain activity (8,14,15,23). Research has demonstratedthe importance and contributions of core stability inhuman movement (12) in producing efficient trunk andlimb actions for the generation, transfer, and control offorces or energy during integrated kinetic chain activities(3,6,8,14,18). For example, Hodges and Richardson (12)examined the sequence of muscle activation during whole-body movements and found that some of the core stabilizers(i.e., transversus abdominis, multifidus, rectus abdominis,and oblique abdominals) were consistently activated beforeany limb movements. These findings support the theorythat movement control and stability are developed ina core-to-extremity (proximal-distal) and a cephalo-caudalprogression (head-to-toe) (8).

Functional movement is the ability to produce andmaintain a balance between mobility and stability alongthe kinetic chain while performing fundamental patternswith accuracy and efficiency (20). Muscular strength,flexibility, endurance, coordination, balance, and move-ment efficiency are components necessary to achievefunctional movement, which is integral to performanceand sport-related skills (8,20). Direct and quantitativemeasures of functional movement are limited; however,Cook (9) proposes qualitative assessment to gain insightabout whether abnormal movements are present, whichpurportedly translate to one’s level of core stability andhow it impacts performance or injury. To determinewhether relationships truly exist between core stabilityand performance, functional movement and individualcomponents of performance, including power, strength,and balance, must be assessed. However, relationshipsbetween these variables have not been established. Oneexplanation for the lack of evidence may be a result of thefact that universal definitions and testing methods do notexist (1,2,20,25,26,28). We hypothesized that there wouldbe a significant relationship between core stability andfunctional movement and between functional movementand performance. Also, a positive relationship wouldexist between core stability and functional movement.

Address correspondence to Tomoko Okada, [email protected].

25(1)/252–261

Journal of Strength and Conditioning Research! 2011 National Strength and Conditioning Association

252 Journal of Strength and Conditioning Researchthe TM

Copyright © National Strength and Conditioning Association Unauthorized reproduction of this article is prohibited.

CS, PERFORMANCE & FUNCTIONAL MOVEMENT?

• To examine in healthy individuals the relationship amongst ...

Core stability

Performance

Functional Movement

• 22 healthy subjects (male & female)

• Amateur athletes from various sports

Okada et al. JSCR 2011


RELATIONSHIP BETWEEN CORE STABILITY,FUNCTIONAL MOVEMENT, AND PERFORMANCE

TOMOKO OKADA, KELLIE C. HUXEL, AND THOMAS W. NESSER

Exercise Physiology Laboratory, Athletic Training Department, Indiana State University, Terre Haute, Indiana

ABSTRACT

Okada, T, Huxel, KC, and Nesser, TW. Relationship between

core stability, functional movement, and performance.

J Strength Cond Res 25(1): 252–261, 2011—The purpose

of this study was to determine the relationship between core

stability, functional movement, and performance. Twenty-eight

healthy individuals (age = 24.4 6 3.9 yr, height = 168.8 6 12.5

cm, mass = 70.2 6 14.9 kg) performed several tests in 3

categories: core stability (flexion [FLEX], extension [EXT], right

and left lateral [LATr/LATl]), functional movement screen (FMS)

(deep squat [DS], trunk-stability push-up [PU], right and left

hurdle step [HSr/HSl], in-line lunge [ILLr/ILLl], shoulder mobility

[SMr/SMl], active straight leg raise [ASLRr/ASLRl], and rotary

stability [RSr/RSl]), and performance tests (backward medicine

ball throw [BOMB], T-run [TR], and single leg squat [SLS]).

Statistical significance was set at p # 0.05. There were

significant correlations between SLS and FLEX (r = 0.500),

LATr (r = 0.495), and LATl (r = 0.498). The TR correlated

significantly with both LATr (r = 0.383) and LATl (r = 0.448).

Of the FMS, BOMB was significantly correlated with HSr (r =

0.415), SMr (r = 0.388), PU (r = 0.407), and RSr (r = 0.391).

The TR was significantly related with HSr (r = 0.518), ILLl

(r = 0.462) and SMr (r = 0.392). The SLS only correlated

significantly with SMr (r = 0.446). There were no significant

correlations between core stability and FMS. Moderate to weak

correlations identified suggest core stability and FMS are not

strong predictors of performance. In addition, existent assess-

ments do not satisfactorily confirm the importance of core stability

on functional movement. Despite the emphasis fitness profes-

sionals have placed on functional movement and core training for

increased performance, our results suggest otherwise. Although

training for core and functional movement are important to include

in a fitness program, especially for injury prevention, they should

not be the primary emphasis of any training program.

KEY WORDS power, agility, muscle endurance

INTRODUCTION

Core stability is achieved through stabilization ofone’s torso, thus allowing optimal production,transfer, and control of force and motion to theterminal segment during an integrated kinetic

chain activity (8,14,15,23). Research has demonstratedthe importance and contributions of core stability inhuman movement (12) in producing efficient trunk andlimb actions for the generation, transfer, and control offorces or energy during integrated kinetic chain activities(3,6,8,14,18). For example, Hodges and Richardson (12)examined the sequence of muscle activation during whole-body movements and found that some of the core stabilizers(i.e., transversus abdominis, multifidus, rectus abdominis,and oblique abdominals) were consistently activated beforeany limb movements. These findings support the theorythat movement control and stability are developed ina core-to-extremity (proximal-distal) and a cephalo-caudalprogression (head-to-toe) (8).

Functional movement is the ability to produce andmaintain a balance between mobility and stability alongthe kinetic chain while performing fundamental patternswith accuracy and efficiency (20). Muscular strength,flexibility, endurance, coordination, balance, and move-ment efficiency are components necessary to achievefunctional movement, which is integral to performanceand sport-related skills (8,20). Direct and quantitativemeasures of functional movement are limited; however,Cook (9) proposes qualitative assessment to gain insightabout whether abnormal movements are present, whichpurportedly translate to one’s level of core stability andhow it impacts performance or injury. To determinewhether relationships truly exist between core stabilityand performance, functional movement and individualcomponents of performance, including power, strength,and balance, must be assessed. However, relationshipsbetween these variables have not been established. Oneexplanation for the lack of evidence may be a result of thefact that universal definitions and testing methods do notexist (1,2,20,25,26,28). We hypothesized that there wouldbe a significant relationship between core stability andfunctional movement and between functional movementand performance. Also, a positive relationship wouldexist between core stability and functional movement.

Address correspondence to Tomoko Okada, [email protected].

25(1)/252–261

Journal of Strength and Conditioning Research! 2011 National Strength and Conditioning Association



CS, PERFORMANCE & FUNCTIONAL MOVEMENT?

• CS assessed through trunk muscle endurance tests (McGill)

• Functional Movement assessed through FMS (Cook)

• Performance ...

Backward Overhead Medicine Ball Throw (BOMB)

T-Run Agility Test (TR)

Single-Leg Squat (SLS)



Performance Assessments

Backward Overhead Medicine Ball Throw. The BOMB wasperformed to assess total-body power (11,28). Stockbruggerand Haennel (27) examined validity and reliability of theBOMB explosive power test. They found that there wasa strong correlation between the distance of the medicine ballthrow and the power index for the countermovement verticaljump (r = 0.906, p , 0.01), and the test-retest reliability of thistest was 0.996 (p , 0.01). A 2.72 kg medicine ball was usedin this study. The test consisted of 4 phases: preparatory,countermovement, upward acceleration, and decelerationphases (Figure 9). Each subject was given 5 practice trialsfor familiarization (11) followed by 3 test trials. The distanceof the medicine ball throw was recorded (m), and the bestthrow was used for the statistical analysis.

T-Run Agility Test (TR). The TR was used to assess agility andspeed (24). Previous research showed that the interclassreliability of the TR was 0.98 when performing 3 trials (24).Subjects ran straight forward and shuffled from left toright and right to left and then ran straight backward ona ‘‘T’’-shaped configuration (Figure 10). Subjects completed2 practice trials followed by 3 test trials. Automatic sensor

TABLE 2. Summary of correlations between core stability, functional movement screen, and performance tests (n = 28).*

BOMB TR SLS

r r2 p r r2 p r r2 p

CSFLEX 0.092 0.01 0.643 20.292 0.09 0.131 0.500† 0.00 0.007EXT 0.052 0.00 0.794 20.188 0.04 0.337 20.063 0.00 0.748LATr 0.152 0.02 0.441 20.383‡ 0.15 0.045 0.495† 0.25 0.007LATl 0.167 0.03 0.397 20.448‡ 0.20 0.017 0.498† 0.25 0.007DS 20.229 0.05 0.241 0.108 0.01 0.585 20.225 0.05 0.249PU 0.407‡ 0.17 0.032 20.331 0.11 0.085 0.355 0.13 0.064HSr 0.415‡ 0.17 0.028 20.518† 0.27 0.005 0.356 0.13 0.063HSl 0.336 0.11 0.080 20.290 0.08 0.135 0.199 0.04 0.310ILLr 0.045 0.00 0.822 20.159 0.03 0.419 0.014 0.00 0.944

FMSILLl 0.361 0.13 0.059 20.462‡ 0.21 0.013 0.175 0.03 0.374SMr 20.388‡ 0.15 0.042 0.392‡ 0.15 0.039 20.446‡ 0.20 0.017SMl 20.055 0.00 0.781 20.099 0.01 0.616 20.246 0.06 0.207ASLRr 0.093 0.01 0.639 20.009 0.00 0.964 0.027 0.00 0.893ASLRl 0.083 0.01 0.674 20.038 0.00 0.848 0.073 0.01 0.710RSr 0.391‡ 0.15 0.040 20.293 0.09 0.130 0.327 0.11 0.089RSl 0.255 0.07 0.191 20.221 0.05 0.260 0.246 0.06 0.327

*CS = core stability; FMS = functional movement screen; BOMB = backward overhead medicine ball throw; TR = T-run; SLS =single leg squat; FLEX = flexion; EXT = extension; LATr = right lateral; LATl = left lateral; DS = deep squat; PU = core stability push-up;HSr = right hurdle step; HSl = left hurdle step; ILLr = right in-line lunge; ILLl = left in-line lunge; SMr = right shoulder mobility; SMl = leftshoulder mobility; ASLRr = right active straight leg raise; ASLRl = left active straight leg raise; RSr = right rotary stability; RSl = left rotarystability.

†p # 0.01.‡p # 0.05.

Figure 10. T-run agility test.


Core Stability, Functional Movement, and Performance




CORE STABILITY AS AN INJURY RISK FACTOR?

• Prospective study

80 females

60 males

• Core stability measures..

Hip abduction isometric strength

Hip external rotation (ER) isometric strength

Modified Biering-Sorensen test (posterior core)

Side bridge test (lateral core)

Core Stability Measures as Risk Factors forLower Extremity Injury in Athletes

DARIN T. LEETUN1, MARY LLOYD IRELAND1, JOHN D. WILLSON2,3,BRYON T. BALLANTYNE2, and IRENE MCCLAY DAVIS2,3

1Kentucky Sports Medicine Clinic, Lexington, KY; 2Joyner Sportsmedicine Institute, Lexington, KY; and 3University ofDelaware, Department of Physical Therapy, Newark, DE

ABSTRACT

LEETUN, D. T., M. L. IRELAND, J. D. WILLSON, B. T. BALLANTYNE, and I. M. DAVIS. Core Stability Measures as Risk Factorsfor Lower Extremity Injury in Athletes.Med. Sci. Sports Exerc., Vol. 36, No. 6, pp. 926–934, 2004. Introduction/Purpose: Decreasedlumbo-pelvic (or core) stability has been suggested to contribute to the etiology of lower extremity injuries, particularly in females. Thisprospective study compares core stability measures between genders and between athletes who reported an injury during their seasonversus those who did not. Finally, we looked for one or a combination of these strength measures that could be used to identify athletesat risk for lower extremity injury. Methods: Before their season, 80 female (mean age ! 19.1 " 1.37 yr, mean weight 65.1 " 10.0kg) and 60 male (mean age ! 19.0 " 0.90 yr, mean weight 78.8 " 13.3 kg) intercollegiate basketball and track athletes were studied.Hip abduction and external rotation strength, abdominal muscle function, and back extensor and quadratus lumborum endurance wastested for each athlete. Results: Males produced greater hip abduction (males ! 32.6 " 7.3%BW, females ! 29.2 " 6.1%BW), hipexternal rotation (males! 21.6" 4.3%BW, females! 18.4" 4.1%BW), and quadratus lumborum measures (males! 84.3" 32.5 s,females ! 58.9 " 26.0 s). Athletes who did not sustain an injury were significantly stronger in hip abduction (males ! 31.6 "7.1%BW, females ! 28.6 " 5.5%BW) and external rotation (males ! 20.6 " 4.2%BW, females ! 17.9 " 4.4%BW). Logisticregression analysis revealed that hip external rotation strength was the only useful predictor of injury status (OR ! 0.86, 95% CI !0.77, 0.097). Conclusion: Core stability has an important role in injury prevention. Future study may reveal that differences in posturalstability partially explain the gender bias among female athletes. Key Words: GENDER, HIP STRENGTH, TRUNK ENDURANCE,BASKETBALL, TRACK

Numerous reports indicate that females who partici-pate in athletics experience particular injuries at adisproportionate rate versus males (14,26,38). Such

injuries include traumatic anterior cruciate ligament (ACL)ruptures to overuse injuries such as patellofemoral painsyndrome, iliotibial band friction syndrome, and femoral,pubic, tibial, and metatarsal stress fracture (14,26,36,38).The identification of risk factors for these lower extremityinjuries continues to interest researchers, health care profes-sionals, and athletes alike.Recent studies suggest that structural differences between

males and females (18,24) may lead to altered movementpatterns that may, in turn, contribute to this gender bias (12).In a study of gender differences in runners, female subjectsdemonstrated greater hip adduction, knee abduction, hip inter-nal rotation, and tibial external rotation during the stance phaseof running (12). The authors felt that these kinematic differ-

ences placed greater demands on female lumbo-pelvic muscu-lature, commonly referred to as the core.Increasingly, scientists are widening their focus to include

assessment of joint mechanics proximal and distal to thesites where injuries tend to occur. This is largely due to theclosed chain nature of athletic activities. When the distalends of a segment are relatively fixed, motion at one seg-ment will influence that of all other segments in the chain.The influence of foot mechanics on proximal structures hasbeen studied extensively (35,39). However, the influence ofproximal stability on lower extremity structure and pathol-ogy remains largely unknown. Bouisset (7) initially pro-posed that stabilization of the pelvis and trunk is necessaryfor all movements of the extremities. Hodges and Richard-son (17) later identified trunk muscle activity before the activ-ity of the lower extremities, which he felt served to stiffen thespine to provide a foundation for functional movements.Considering the wide variety of movements associated

with athletics, athletes must possess sufficient strength inhip and trunk muscles that provide stability in all threeplanes of motion. Indeed, recent research demonstrates thatthe contribution of different muscle groups to lumbar spinestability depends on the direction and magnitude of trunkloading (10). The abdominal muscles control external forcesthat may cause the spine to extend, laterally flex, or rotate(2). The abdominals have also been reported to increase thestability of the spine through co-contraction with the lumbarextensors (2). Ireland (19) further suggests that the abdomi-

Address for correspondence: John D. Willson, MSPT, University of Del-aware, Department of Physical Therapy, 305 McKinly Lab, Newark, DE19716; E-mail: [email protected] for publication November 2003.Accepted for publication January 2004.

0195-9131/04/3606-0926MEDICINE & SCIENCE IN SPORTS & EXERCISE®Copyright © 2004 by the American College of Sports Medicine

DOI: 10.1249/01.MSS.0000128145.75199.C3

926

Leetun et al. AJSM 2004


Hip abduction isometric strength testing was performedwith subjects positioned in sidelying on a treatment table(Fig. 1). A pillow was placed between the subjects’ legs,using additional toweling as needed, such that the hip of theleg to be tested was abducted approximately 10° as mea-sured with respect to a line connecting the anterior superioriliac spines. A strap placed just proximal to the iliac crestand secured firmly around the underside of the table wasused to stabilize the subjects’ trunk. The center of the forcepad of a Nicholas hand-held dynamometer (Lafayette In-struments, Lafayette, IN) was then placed directly over amark located 5 cm proximal to the lateral knee joint line.This dynamometer uses a load cell force detecting system tomeasure static force ranging from 0 to 199.9 kg with accu-racy to 0.1 kg ! 2%. The dynamometer was secured be-tween the leg and a second strap that was wrapped aroundthe leg and the underside of the table. The strap eliminatedthe effect of tester strength on this measure which has beenreported to be a limitation of hand-held dynamometry (4).After zeroing the dynamometer, the subject was instructed

to push the leg upward with maximal effort for 5 s. Theforce value displayed on the dynamometer was recorded andthe device was re-zeroed. One practice trial and three ex-perimental trials were performed, with 15 s of rest betweentrials. The peak value from the three experimental trials wasrecorded. The athlete was then repositioned on their oppo-site side to test the hip strength of the contralateral limbusing the same procedures.Hip external rotation (ER) isometric strength testing was

performed with subjects positioned on a padded chair withthe hips and knees flexed to 90° (Fig. 2). To limit the contri-bution of the hip adductors to force production in rotation, astrap was used to stabilize the thigh of the involved leg and atowel roll was placed between the subjects’ knees. The dyna-mometer was then placed such that the center of the force padwas directly over a mark that was 5 cm proximal to the medialmalleolus. A strap around the leg and around the base of astationary object held the dynamometer in place during con-tractions. Collection of peak hip external rotation isometricstrength for each leg then proceeded in the samemanner as thatfor hip abduction strength.Muscle capacity of the posterior core was measured using

the modified Biering-Sorensen test (30) (Fig. 3). The athletewas positioned in prone with the pelvis at the edge of atreatment table. Straps were used to secure the athletes’pelvis and legs to the table. The athlete supported their torsowith their hands on a bench in front of the table until they

FIGURE 2—Isometric testing of hip external rotation strength usinghand-held dynamometry and strap stabilization.

FIGURE 1—Isometric testing of hip abduction strength using hand-held dynamometry and strap stabilization.

928 Official Journal of the American College of Sports Medicine http://www.acsm-msse.org

Hip abduction isometric strength testing was performedwith subjects positioned in sidelying on a treatment table(Fig. 1). A pillow was placed between the subjects’ legs,using additional toweling as needed, such that the hip of theleg to be tested was abducted approximately 10° as mea-sured with respect to a line connecting the anterior superioriliac spines. A strap placed just proximal to the iliac crestand secured firmly around the underside of the table wasused to stabilize the subjects’ trunk. The center of the forcepad of a Nicholas hand-held dynamometer (Lafayette In-struments, Lafayette, IN) was then placed directly over amark located 5 cm proximal to the lateral knee joint line.This dynamometer uses a load cell force detecting system tomeasure static force ranging from 0 to 199.9 kg with accu-racy to 0.1 kg ! 2%. The dynamometer was secured be-tween the leg and a second strap that was wrapped aroundthe leg and the underside of the table. The strap eliminatedthe effect of tester strength on this measure which has beenreported to be a limitation of hand-held dynamometry (4).After zeroing the dynamometer, the subject was instructed

to push the leg upward with maximal effort for 5 s. Theforce value displayed on the dynamometer was recorded andthe device was re-zeroed. One practice trial and three ex-perimental trials were performed, with 15 s of rest betweentrials. The peak value from the three experimental trials wasrecorded. The athlete was then repositioned on their oppo-site side to test the hip strength of the contralateral limbusing the same procedures.Hip external rotation (ER) isometric strength testing was

performed with subjects positioned on a padded chair withthe hips and knees flexed to 90° (Fig. 2). To limit the contri-bution of the hip adductors to force production in rotation, astrap was used to stabilize the thigh of the involved leg and atowel roll was placed between the subjects’ knees. The dyna-mometer was then placed such that the center of the force padwas directly over a mark that was 5 cm proximal to the medialmalleolus. A strap around the leg and around the base of astationary object held the dynamometer in place during con-tractions. Collection of peak hip external rotation isometricstrength for each leg then proceeded in the samemanner as thatfor hip abduction strength.Muscle capacity of the posterior core was measured using

the modified Biering-Sorensen test (30) (Fig. 3). The athletewas positioned in prone with the pelvis at the edge of atreatment table. Straps were used to secure the athletes’pelvis and legs to the table. The athlete supported their torsowith their hands on a bench in front of the table until they

FIGURE 2—Isometric testing of hip external rotation strength usinghand-held dynamometry and strap stabilization.

FIGURE 1—Isometric testing of hip abduction strength using hand-held dynamometry and strap stabilization.


were instructed to cross their arms and assume a horizontalposition. The athlete was required to maintain the body in ahorizontal position for as long as possible. The total timethat the athlete was able to maintain the horizontal positionuntil they touched down on the bench in front of them withtheir hands was recorded in seconds using a stopwatch.Athletes performed the side bridge test as described by

McGill et al. (30) as a measure of lateral core musclecapacity, particularly the quadratus lumborum (Fig. 4). Theathletes were positioned in right sidelying with their top footin front of their bottom foot and their hips in zero degrees offlexion. The athletes were asked to lift their hips off thetreatment table, using only their feet and right elbow forsupport. The left arm was held across their chest with theirhand placed on the right shoulder. The total time the athletewas able lift their bottom hip from the table was recordedusing a stopwatch. McGill (30) previously documented nosignificant difference between right and left side bridgeendurance times. Therefore, the measure for the right lateralcore muscles was used for data analysis.Anterior core muscle testing was performed using the

straight leg lowering test for the first year of testing (23).

This test was performed with the patient supine on thetreatment table with their hips flexed to 90° and their kneesfully extended. Patients were asked to steadily lower theirlegs back to the table over a 10-s period while they main-tained contact with the examiner’s hand at their L4–L5interspace. A large board was placed behind the athleteduring this test with marks indicating 10° increments of hipflexion. The angle at which the athlete’s low back raisedfrom the examiner’s hand was recorded. Lower angles ofhip flexion indicate a better performance on the test.After 1 yr of testing, we questioned the sensitivity of the

straight leg lowering test for this population of subjects.There was very little variability in the measurement asnearly 70% of the athletes raised from the examiner’s handbetween 50° and 60° of hip flexion, making the effect sizesmall and increasing our likelihood of Type II error. There-fore, subjects enrolled in the second year of testing per-formed the flexor endurance test as described by McGill etal. (30) This test is performed seated on a treatment tablewith the athlete’s back supported on a 60° wedge (measuredfrom horizontal). The athlete’s hands were crossed overtheir chest and their toes were placed under a stabilizationstrap. The athletes were then asked to maintain the positionas the supporting wedge was pulled 10 cm away from theathlete. The time the athlete was able to maintain the 60°angle was recorded using a stopwatch. The test endedwhen the angle of the athlete’s upper body fell below the60° threshold. Based on a larger range of evenly distrib-uted values, we found this test to be a more sensitiveindicator of anterior core muscle capacity than thestraight leg lowering test.

Injuries. The head athletic trainers for each of the teamsparticipating in the study recorded all back and lower ex-tremity injuries that occur during organized practices orgames throughout the season. An injury was defined as anevent that occurred during athletic participation and re-quired treatment or attention from the athletic trainer, teamdoctor, or other medical staff. Further, the event must haveresulted in at least one full missed day of practice or sportparticipation. Trainers were given identical forms to recordthe details of each injury including the date, conditions(practice or game environment), mechanism of injury (con-tact with another player or object vs no contact), body partinvolved, and the type of injury that occurred. Finally, thenumber of whole days lost due to injury was recorded foreach injury.

Data analysis. Core stability measurements were com-pared between genders and between athletes who reportedand injury and those who did not using two analysis ofvariance tests (SPSS 11.5.1, Chicago, IL). A significancelevel of 0.05 was used for all comparisons. The results ofabdominal muscle performance for both tests are presenteddescriptively but were not included in the statistical analysisdue to the previously described change in methods andassociated lack of power for comparison. Logistic regres-sion was used to analyze the relationship between injurystatus and postural muscle strength measurements. The pro-cess began with simultaneous entry of the independent con-

FIGURE 4—Endurance testing of the lateral trunk using the sidebridge test. Left side test position shown here.

FIGURE 3—Endurance testing of lumbar extensors using the modi-fied Beiring-Sorensen test.

CORE STABILITY IN ATHLETES Medicine & Science in Sports & Exercise! 929

Isometric testing of hip abduction strength using hand-held dynamometry and strap stabilization

Isometric testing of hip external

rotation strength using hand-held

dynamometry and strap stabilization

Endurance testing of lumbar extensors using the modified

Beiring-Sorensen test

were instructed to cross their arms and assume a horizontalposition. The athlete was required to maintain the body in ahorizontal position for as long as possible. The total timethat the athlete was able to maintain the horizontal positionuntil they touched down on the bench in front of them withtheir hands was recorded in seconds using a stopwatch.Athletes performed the side bridge test as described by

McGill et al. (30) as a measure of lateral core musclecapacity, particularly the quadratus lumborum (Fig. 4). Theathletes were positioned in right sidelying with their top footin front of their bottom foot and their hips in zero degrees offlexion. The athletes were asked to lift their hips off thetreatment table, using only their feet and right elbow forsupport. The left arm was held across their chest with theirhand placed on the right shoulder. The total time the athletewas able lift their bottom hip from the table was recordedusing a stopwatch. McGill (30) previously documented nosignificant difference between right and left side bridgeendurance times. Therefore, the measure for the right lateralcore muscles was used for data analysis.Anterior core muscle testing was performed using the

straight leg lowering test for the first year of testing (23).

This test was performed with the patient supine on thetreatment table with their hips flexed to 90° and their kneesfully extended. Patients were asked to steadily lower theirlegs back to the table over a 10-s period while they main-tained contact with the examiner’s hand at their L4–L5interspace. A large board was placed behind the athleteduring this test with marks indicating 10° increments of hipflexion. The angle at which the athlete’s low back raisedfrom the examiner’s hand was recorded. Lower angles ofhip flexion indicate a better performance on the test.After 1 yr of testing, we questioned the sensitivity of the

straight leg lowering test for this population of subjects.There was very little variability in the measurement asnearly 70% of the athletes raised from the examiner’s handbetween 50° and 60° of hip flexion, making the effect sizesmall and increasing our likelihood of Type II error. There-fore, subjects enrolled in the second year of testing per-formed the flexor endurance test as described by McGill etal. (30) This test is performed seated on a treatment tablewith the athlete’s back supported on a 60° wedge (measuredfrom horizontal). The athlete’s hands were crossed overtheir chest and their toes were placed under a stabilizationstrap. The athletes were then asked to maintain the positionas the supporting wedge was pulled 10 cm away from theathlete. The time the athlete was able to maintain the 60°angle was recorded using a stopwatch. The test endedwhen the angle of the athlete’s upper body fell below the60° threshold. Based on a larger range of evenly distrib-uted values, we found this test to be a more sensitiveindicator of anterior core muscle capacity than thestraight leg lowering test.

Injuries. The head athletic trainers for each of the teamsparticipating in the study recorded all back and lower ex-tremity injuries that occur during organized practices orgames throughout the season. An injury was defined as anevent that occurred during athletic participation and re-quired treatment or attention from the athletic trainer, teamdoctor, or other medical staff. Further, the event must haveresulted in at least one full missed day of practice or sportparticipation. Trainers were given identical forms to recordthe details of each injury including the date, conditions(practice or game environment), mechanism of injury (con-tact with another player or object vs no contact), body partinvolved, and the type of injury that occurred. Finally, thenumber of whole days lost due to injury was recorded foreach injury.

Data analysis. Core stability measurements were com-pared between genders and between athletes who reportedand injury and those who did not using two analysis ofvariance tests (SPSS 11.5.1, Chicago, IL). A significancelevel of 0.05 was used for all comparisons. The results ofabdominal muscle performance for both tests are presenteddescriptively but were not included in the statistical analysisdue to the previously described change in methods andassociated lack of power for comparison. Logistic regres-sion was used to analyze the relationship between injurystatus and postural muscle strength measurements. The pro-cess began with simultaneous entry of the independent con-

FIGURE 4—Endurance testing of the lateral trunk using the sidebridge test. Left side test position shown here.

FIGURE 3—Endurance testing of lumbar extensors using the modi-fied Beiring-Sorensen test.


Endurance testing of the lateral trunk using the side bridge test

(left side test position)



ables established that hip external rotation was the onlyuseful predictor of the likelihood of sustaining an injuryover the course of a season (coefficient! "0.154, t-statistic! "3.15, P ! 0.002). However, the relatively low coeffi-cient of determination suggests that other factors not in-cluded in this study significantly contribute to injury statusover the course of an athletic season.

DISCUSSION

The purpose of this study was to prospectively examinedifferences in core stability measures between males andfemales as well as between those athletes who becameinjured and those who did not. We also hoped to identify oneor a combination of strength measures that could be used toidentify those individuals at risk for lower extremity injury.Females in this study demonstrated significantly reduced

side bridge endurance and hip abduction and external rota-tion isometric strength. Whereas weakness in females hasbeen previously documented in these muscles groups(5,8,30), the consequence of this weakness is not well un-derstood. We suggest that hip and trunk weakness reducesthe ability to of females stabilize the hip and trunk. There-fore, females may be more vulnerable to the large externalforces experienced by these segments during athletics, es-pecially those forces in the transverse and frontal planes. Asa result, females may be predisposed to excessive motion inthe hip or trunk versus males, potentially permitting theirentire lower extremity to move into positions frequentlyassociated with noncontact injuries such as femoral adduc-tion and internal rotation. Indeed, recent literature verifiesthat females tend to display greater hip internal rotation andadduction during athletic tasks (12,22,25).Athletes who sustained an injury in this study displayed

significantly less hip abduction and external rotationstrength than uninjured athletes. To our knowledge, this isthe first prospective study to demonstrate a relationshipbetween these variables. However, several retrospective andcross-sectional studies have been performed that previouslyindicated that such a relationship may exist for a variety ofinjuries (1,13,20,21). For example, Ireland et al. (20) iden-tified significant weakness among young female athletes

with patellofemoral pain in hip abduction and external ro-tation strength versus a healthy, age-matched control group.These authors further explained that the mechanism for thispain may be excessive femoral adduction and internal rota-tion during weight bearing activities. Citing cadaveric stud-ies, they reported that this alignment promotes lateral pa-tellar tracking and increases lateral retropatellar contactpressure (20).This study finds that hip external rotation strength weak-

ness most closely predicts injury status over the course ofone athletic season. However, hip external rotation strengthis only one element of core stability, and other elements ofcore stability not included in this study may add to thepredictive value of the regression equation. Core stability isthe product of motor control and muscular capacity of thelumbo-pelvic-hip complex. Hewett et al. (16) has previouslydemonstrated the value of motor control on knee injuryprevention. Females who participated in a general strength,flexibility, and neuromuscular training program experienceda 62% decrease in serious knee ligament injuries. Althoughthe strengthening component of his intervention programincluded abdominal curls and back hyperextension exer-cises, our results suggest that these muscle groups may nothave significantly contributed to his positive results. Rather,the benefit of his program may be a reduction in kneeadduction and abduction moments due to advanced posturaladaptations of the hip abductors and external rotators beforelanding from a jump.The other component of core stability, muscle capacity, is

represented by the athlete’s ability to generate force ormaintain force (endurance) in the lumbo-pelvic-hip complex.McGill et al. (29) suggest that the value of trunk muscleendurance is greater than the ability of these muscles to gen-erate force in the prevention of low back pain. Indeed, theendurance of the trunk extensors has been found to predict theoccurrence of low back pain among 30- to 60-yr-old adults (3).However, in a more athletic population, this study suggests thatisometric hip strength measures, particularly in external rota-tion, are more accurate predictors of back and lower extremityinjury than trunk endurance measures.These results may reflect the significance of strength

versus endurance for individuals who participate in high

TABLE 4. Comparison of core stability measures by sport.

Hip Abduction(% Body Weight)

Hip External Rotation(% Body Weight) Side Bridge (s) Back Extension (s)

Average (SD) Average (SD) Average (SD) Average (SD)

Male BB (N ! 44) 32.9 (7.8) 21.7 (4.3) 82.7 (30.6) 131.4 (42.0)Male XC (N ! 17) 32.4 (6.2) 21.7 (4.3) 87.6 (37.1) 122.9 (38.7)Female BB (N ! 60) 29.3 (5.8) 18.0 (3.5) 57.8 (24.7) 115.7 (43.5)Female XC (N ! 18) 27.8 (7.0) 19.5 (5.3) 60.9 (30.5) 151.4 (52.5)

TABLE 5. Comparison of core stability measures by injury status.




Uninjured (N ! 99) 31.6 (7.1) 20.6 (4.2) 72.0 (32.4) 128.3 (43.6)Injured (N ! 41) 28.6 (5.5) 17.9 (4.4) 64.7 (28.8) 121.6 (48.9)P 0.02 0.001 0.22 0.43



DISCUSSION




















DISCUSSION



















CORE STABILITY BY INJURY STATUS



LOGISTIC REGRESSIONINJURY STATUS AS DEPENDENT VARIABLE

speed events. Cholewicki et al. (9) suggest that the kine-matic response of the trunk during sudden events dependson both the mechanical stability level of the spine beforeloading, as well as the reflex response of the trunk musclesimmediately after loading. Considering that the endurancetimes between the injured and uninjured athletes were verysimilar, it appears that all athletes possessed the capacity formechanical stability of the lumbar spine. However, asCholewicki et al. (9) suggest, the injured athletes may lackthe ability to generate sufficient force or resist externalforces during high-speed events. Perhaps future study willfind that isometric strength testing of the abdominals, backextensors, and quadratus lumborum is more closely associ-ated with the ability of individuals to sufficiently recruit themuscles of the trunk during high speed events, stabilize thelumbar spine, and prevent lower extremity injuries.The athletes in this study experienced an injury incidence

of 0.35 (48 injuries/139 athletes). This incidence is verysimilar to the results of Messina et al. (32), who analyzedinjuries sustained by male and female Texas high schoolbasketball players. After adjustment to include only backand lower extremity injuries, the injury incidence for theirstudy becomes 0.37 injuries/athlete. Meeuwisse et al. (31)reported that the incidence of back and lower extremityinjuries was 0.50 injuries/athlete for their male intercolle-giate basketball players. Although the males in our study ex-perienced a much lower injury incidence of 0.23 injuries/athlete, we only included injuries that resulted in at least onefull day of missed participation. Meeuwisse et al. also includedinjuries that resulted in days of partially missed participation.The injury patterns in this investigation mirror those

found in other, large-scale epidemiological studies. For ex-ample, a greater proportion of female athletes experiencedan injury versus males (36,37,42). Additionally, the anklewas the most commonly injured structure of the lowerextremity (31,32,42). Finally, a greater total number ofinjuries occurred during practice than during games(31,34,36). These results suggest that our sample of injuriesrepresent a similar distribution of injuries for this populationof athletes.A potential limitation of this study is that hip strength

measurements were made in units of force instead of torque.Therefore, if injured athletes were systematically taller than

the uninjured athletes, the difference in hip torque measure-ments may have been less significant than the force mea-surements found in this study. However, considering thatfemales tend to be shorter than males and a greater propor-tion of females reported injuries, we believe we would havefound even greater differences between groups with respectto gender and injury status if torque were used.A second potential limitation of this study is that the two

examiners were not tested for intratester reliability beforedata collection. However, as noted above, each test wasbased on those previously described to be reliable in asimilar group of subjects. Further, the use of straps forstabilization during isometric testing eliminated the variabil-ity of tester strength in these measures. Finally, the testerswere aware of the potential influence of verbal feedback onthe motivation of the subjects and used consistent verbalcues for all endurance tests. Intertester reliability was not aconcern because each tester performed the same teststhroughout data collection.The results of this investigation generate numerous ques-

tions for further studies. For example, future studies maytest the athlete’s ability to demonstrate core stability in morephysiologic positions. The tests positions used in this studyare those most commonly used for manual muscle testingand are conducive to methods for preparticipation screening.Although these tests gauge the capacity of each athlete togenerate force or maintain force in core muscle groups, theydo not necessarily reflect how these muscles function duringclosed chain activities. Further, these tests may not reflectthe degree to which the muscles are recruited by the athletesduring athletic participation. Considering these facts, futurestudies should consider the addition of a dynamic test oflower extremity alignment during a closed kinetic chainactivity such as the single leg step down test (41). Futurestudies should also seek to understand the relationship be-tween these core strength measures and the result of thisdynamic test.Future studies on the potential of core stability programs

to prevent serious knee ligament injuries also seem justified.

TABLE 6. Description of the core stability measurements for a female subject prior to an ACL injury.




Uninjured females 29.4 (6.2) 19.0 (3.8) 59.0 (23.3) 124.3 (46.1)Injured females 28.9 (6.1) 17.4 (4.6) 58.8 (30.1) 121.7 (54.2)Female with ACL injury 23.0 16.5 25.0 38.0

TABLE 7. Pearson correlation matrix for core stability measures.

Hipabduction

Hip ExtRotation

SideBridge

Hip ext rotation 0.525*Side bridge 0.383* 0.440*Back extension 0.165 0.087 0.564*

* Significant at P ! 0.05.

TABLE 8. Logistic regression results (dependent variable " injury duringthe season).

Variable Coefficient t POddsRatio (95% CI OR)

Constant 2.931 2.37 0.018Hip abduction #0.031 #0.85 0.40 0.97 (0.90, 1.04)Hip external rotation #0.146 #2.49 0.013 0.86 (0.77, 0.97)Side bridge 0.007 0.73 0.46 1.01 (0.99, 1.02)Back extension #0.004 #0.77 0.44 1.00 (0.99, 1.01)

Likelihood ratio [df] 12.72 [4] 0.013% correct prediction 62.6%McFadden’s-R2 0.076




MULTICOMPONENT INTERVENTIONSTHE 11+

• comprehensive warmup program designed to reduce the risk of injuries

Strength, plyometrics, balancePlank, Side plank, Nordic hamstring, Single leg balance, Squat, Jumping


RESEARCH

Comprehensive warm-up programme to prevent injuriesin young female footballers: cluster randomisedcontrolled trial

Torbjørn Soligard, PhD student,1 Grethe Myklebust, associate professor,1 Kathrin Steffen, research fellow,1

Ingar Holme, professor,1 Holly Silvers, physical therapist,2 Mario Bizzini, physical therapist,3 Astrid Junge,associate professor,3 Jiri Dvorak, professor,3 Roald Bahr, professor,1 Thor Einar Andersen, associateprofessor1

ABSTRACTObjective To examine theeffect of a comprehensivewarm-

up programme designed to reduce the risk of injuries in

female youth football.

Design Cluster randomised controlled trial with clubs as

the unit of randomisation.

Setting 125 football clubs from the south, east, and

middle of Norway (65 clusters in the intervention group;

60 in the control group) followed for one league season

(eight months).

Participants 1892 female players aged 13-17 (1055

players in the intervention group; 837 players in the

control group).

Intervention A comprehensive warm-up programme to

improve strength, awareness, and neuromuscular control

during static and dynamic movements.

Main outcome measure Injuries to the lower extremity

(foot, ankle, lower leg, knee, thigh, groin, and hip).

Results During one season, 264 players had relevant

injuries: 121 players in the intervention group and 143 in

the control group (rate ratio 0.71, 95%confidence interval

0.49 to 1.03). In the intervention group there was a

significantly lower risk of injuries overall (0.68, 0.48 to

0.98), overuse injuries (0.47, 0.26 to 0.85), and severe

injuries (0.55, 0.36 to 0.83).

Conclusion Though the primary outcome of reduction in

lowerextremity injurydidnot reachsignificance, the riskof

severe injuries, overuse injuries, and injuries overall was

reduced. This indicates that a structured warm-up

programme can prevent injuries in young female football

players.

Trial registration ISRCTN10306290.

INTRODUCTION

Football (soccer) is the most popular team sport in theworld. There are already more than 265 millionregistered players, and the number of participants iscontinuing to grow.1 In particular, the number ofwomen players is increasing rapidly.1 Playing football,however, entails a substantial risk of injury, and studieson elite and non-elite female footballers have reported

rates of injury similar to those in men,2-11 the mostcommon being injuries to the knee and ankle ligamentand thigh muscle strains.2-9 11 12 Women might even beat greater risk of serious injury than men; the rate ofanterior cruciate ligament injuries is three to five timeshigher for girls than for boys.13 14

The high injury rate among football players ingeneral and female players in particular constitutes aconsiderable problem for the player, the club, and—given the popularity of the sport—for society at large.Health consequences are seen not just in the short termbut also in the dramatic increase in the risk of earlyosteoarthritis.15-17 Despite the urgent need to developprogrammes to prevent knee and ankle injuries infootballers, there exist only a few small or non-randomised studies on prevention of injury in femalefootball players.18-20

In a recent randomisedcontrolled trial,we examinedthe effect of a structured training programme (“The11”)21 over one season among 2000 female playersaged 13-17.22 The intervention consisted of exercisesfocusing on core stability, balance, dynamic stabilisa-tion, and eccentric hamstring strength. We found nodifference in the injury risk between the interventiongroup and control group, though the study was limitedby low compliance among the intervention teams.This led us to develop an exercise programme to

improve both the preventive effect of the programmeand the compliance of coaches and players. Therevised programme (“The 11+”) included key exer-cises and additional exercises to provide variation andprogression. It also included a new set of structuredrunning exercises that made it better suited as acomprehensive warm-up programme for training andmatches.We conducted a randomised controlled trial to

examine theeffect of the revisedprogrammeon ratesoflower extremity injury in young female footballers. Tominimise contamination bias within clubs, we used acluster randomised design.

1Oslo Sports Trauma ResearchCentre, Norwegian School ofSport Sciences, PO Box 4014Ullevaal Stadion, 0806 Oslo,Norway2Santa Monica Orthopaedic andSports Medicine ResearchFoundation, 1919 Santa MonicaBlvd, Suite 350, Santa Monica,CA 90404 USA3FIFA Medical Assessment andResearch Centre, SchulthessClinic, Lengghalde 2, CH-8008Zurich, Switzerland

Correspondence to: T [email protected]

Cite this as: BMJ 2008;337:a2469doi:10.1136/bmj.a2469

BMJ | ONLINE FIRST | bmj.com page 1 of 91476

A Randomized Controlled Trial to PreventNoncontact Anterior Cruciate LigamentInjury in Female Collegiate Soccer PlayersJulie Gilchrist,*† MD, Bert R. Mandelbaum,‡ MD, Heidi Melancon,§ MPH,George W. Ryan,|| PhD, Holly J. Silvers,‡ MPT, Letha Y. Griffin,¶ MD, PhD,Diane S. Watanabe,‡ MA, ATC, Randall W. Dick,# MS, and Jiri Dvorak,** MDFrom the †Division of Unintentional Injury Prevention, National Center for Injury Prevention &Control, Centers for Disease Control & Prevention, Atlanta, Georgia, ‡Santa MonicaOrthopedic & Sports Medicine Research Foundation, Santa Monica, California, the§National Recreation and Park Association, Ashburn, Virginia, the ||Office of Statisticsand Programming, National Center for Injury Prevention & Control, Centers for DiseaseControl & Prevention, Atlanta, Georgia, ¶Peachtree Orthopedics, Atlanta, Georgia,the #National Collegiate Athletic Association, Indianapolis, Indiana, and the**Fédération Internationale de Football Association (FIFA), Medical Assessment and ResearchCenter, Schulthess Clinic, Zurich, Switzerland.

Background: Neuromuscular and proprioceptive training programs can decrease noncontact anterior cruciate ligament injuries;however, they may be difficult to implement within an entire team or the community at large.

Hypothesis: A simple on-field alternative warm-up program can reduce noncontact ACL injuries.

Study Design: Randomized controlled trial (clustered); Level of evidence, 1.

Methods: Participating National Collegiate Athletic Association Division I women’s soccer teams were assigned randomly tointervention or control groups. Intervention teams were asked to perform the program 3 times per week during the fall 2002 sea-son. All teams reported athletes’ participation in games and practices and any knee injuries. Injury rates were calculated basedon athlete exposures, expressed as rate per 1000 athlete exposures. A z statistic was used for rate ratio comparisons.

Results: Sixty-one teams with 1435 athletes completed the study (852 control athletes; 583 intervention). The overall anteriorcruciate ligament injury rate among intervention athletes was 1.7 times less than in control athletes (0.199 vs 0.340; P = .198;41% decrease). Noncontact anterior cruciate ligament injury rate among intervention athletes was 3.3 times less than in controlathletes (0.057 vs 0.189; P = .066; 70% decrease). No anterior cruciate ligament injuries occurred among intervention athletesduring practice versus 6 among control athletes (P = .014). Game-related noncontact anterior cruciate ligament injury rates inintervention athletes were reduced by more than half (0.233 vs 0.564; P = .218). Intervention athletes with a history of anteriorcruciate ligament injury were significantly less likely to suffer another anterior cruciate ligament injury compared with control ath-letes with a similar history (P = .046 for noncontact injuries).

Conclusion: This program, which focuses on neuromuscular control, appears to reduce the risk of anterior cruciate ligamentinjuries in collegiate female soccer players, especially those with a history of anterior cruciate ligament injury.

Keywords: RCT; ACL; soccer; injuries

*Address correspondence to Julie Gilchrist, MD, CDC/NCIPC, Division of Unintentional Injury Prevention, 4770 Buford Hwy, MS F62, Atlanta, GA 30341(e-mail: [email protected]).

Presented at the interim meeting of the AOSSM, San Francisco, California, March 2004.Dr. Mandelbaum, Ms. Silvers, and Ms. Watanabe, employees of Santa Monica Orthopedic and Sports Medicine Research Foundation (SMOSMRF),

were involved with the development of the PEP Program under evaluation in this study but have no financial interest in the PEP Program and did notparticipate in data collection or analysis. Ms. Melancon was employed by the SMOSMRF and participated in data collection and analysis.

The American Journal of Sports Medicine, Vol. 36, No. 8DOI: 10.1177/0363546508318188© 2008 American Orthopaedic Society for Sports Medicine

Soligard et al. BMJ 2008Gilchrist et al. AJSM 2008

~50% reduction of risk for non contact LE injurieshow much is due to core stability components?


Performance aspects of an injury prevention program: a ten-weekintervention in adolescent female football players

K. Steffen, H. M. Bakka, G. Myklebust, R. Bahr

Department of Sports Medicine, Oslo Sports Trauma Research Center, Norwegian School of Sport Sciences, Oslo, NorwayCorresponding author: Kathrin Steffen, Department of Sports Medicine, Oslo Sports Trauma Research Center, NorwegianSchool of Sport Sciences, P.O. Box 4014 Ulleval Stadion, 0806 Oslo, Norway. Fax: 147 23 26 23 07, E-mail:[email protected]

Accepted for publication 10 May 2007

The injury rate in football is high, and effective injuryprevention methods are needed. An exercise program, the‘‘11,’’ has been designed to prevent the most common injurytypes in football. However, the effect of such a program onperformance is not known. The aim of this randomized-controlled trial was to investigate the effect of the ‘‘11’’ onperformance after a 10-week training period. Thirty-fouradolescent female football players were randomly assignedto either an intervention (n5 18) or a control group(n5 16). The ‘‘11’’ is a 15-min program consisting of tenexercises for core stability, lower extremity strength, bal-

ance and agility. Performance tests included isokinetic andisometric strength protocols for the quadriceps and ham-strings, isometric hip adduction and abduction strength,vertical jump tests, sprint running and soccer skill tests.There was no difference between the intervention andcontrol groups in the change in performance from the pre-to post-test for any of the tests used. In conclusion, no effectwas observed on a series of performance tests in a group ofadolescent female football players using the ‘‘11’’ as astructured warm-up program.

Background

Football is probably the most popular sport world-wide, with a growing interest and an increasingnumber of female players in particular (NorwegianFootball Association, 2005). It is a contact sport andchallenges physical fitness by requiring a variety ofskills at different intensities. Running is the predo-minant activity, and explosive efforts during sprints,duels, jumps and kicks are important performancefactors, requiring maximal strength and anaerobicpower of the neuromuscular system (Wisløff et al.,1998; Cometti et al., 2001; Reilly & Gilbourne, 2003;Hoff & Helgerud, 2004).Unfortunately, the game is associated with a high

risk of injuries, which results in significant costs forthe public health system (de Loes et al., 2000) andmay even cause long-term disability for the injuredplayer (Lohmander et al., 2004; von Porat et al.,2004; Myklebust & Bahr, 2005). Serious knee inju-ries, such as anterior cruciate ligament injuries, are ofparticular concern in female team sports (Powell &Barber-Foss, 2000; Myklebust et al., 2003; Agel etal., 2005; Olsen et al., 2005). Consequently, there isevery reason to emphasize the prevention of injuriesin football, and to develop and implement prevention

programs for young players as early in their career aspossible.Several programs have successfully incorporated

one or more exercise components, including plyo-metrics, strength, neuromuscular training, runningand cutting movement patterns, to prevent injuries infemale (Hewett et al., 1999; Heidt et al., 2000;Myklebust et al., 2003; Mandelbaum et al., 2005;Olsen et al., 2005) and male athletes (Askling et al.,2003). However, compliance is a concern (Myklebustet al., 2003), and it may be difficult to motivatecoaches and players to follow such exercise programsmerely to prevent injuries, unless there is a directeffect performance benefit as well.Exercises used in prevention protocols have also

been shown to have performance effects among malefootball players, such as increased strength (Asklinget al., 2003; Mjølsnes et al., 2004). Core stabilityexercises may improve technical skills and totalawareness of the game (Holm et al., 2004; Leetunet al., 2004; Paterno et al., 2004). Comprehensiveneuromuscular training programs that combine plyo-metrics, core strengthening, balance, resistance orspeed/agility training may improve several measuresof performance concomitantly and at the same timeimprove biomechanical measures related to lower

Scand J Med Sci Sports 2008: 18: 596–604 Copyright & 2007 The Authors

Journal compilation & 2007 Blackwell MunksgaardPrinted in Singapore .All rights reservedDOI: 10.1111/j.1600-0838.2007.00708.x

596

PERFORMANCE ENHANCEMENT?

• No significant effects were observed on different performance variables among players participating in a 10-week injury prevention program, compared with players who trained as usual

more intense training stimulus needed?

34 adolescent female football players from two elite sport high schools

Steffen et al. SJMSS 2008



HEALTH BENEFITS VS HEALTH RISK

Type and amount of activity

Novice runners

RecreationalRunnersmales

RecreationalRunnersfemales

Competitiverunners

Marathonrunners

2.562.55-2.60

2.062.02-2.10 1.80

1.70-1.90 1.551.54-1.56

1.101.09-1.20

Tonoli et al. 2010


• General preventive approach lies in reducing the load or increasing loading capacity to reduce risk for RRI

• However ... specific loads leading up to RRI are biomechanically different and caused by local overloading

• An individual set of weak links that predispose to injury?

OVERLOADING THE SYSTEM?


ILL-LOADING?

914 | december 2011 | volume 41 | number 12 | journal of orthopaedic & sports physical therapy

[ CASE REPORT ]

Patellofemoral pain (PFP) is one of the most common overuse injuries of the lower extremity. It affects 10% to 20% of the general population18 and is associated with higher risk of injury in active females.34 The findings of a previous study suggested

that a history of PFP increases the risk for subsequent development of patellofemoral osteoarthritis.35 The nature of PFP is multifactorial, and many risk factors have been associated with this condition.5,10 Locally,

imbalance of the quadriceps muscula-ture25 and maltracking of the patella24 are 2 potential factors that may lead to

! STUDY DESIGN: Case series.

! BACKGROUND: Patellofemoral pain is a com-mon overuse injury in runners. Recent findings suggest that patellofemoral pain is related to high-impact loading associated with a rearfoot strike pattern. This case series describes the potential training effects of a landing pattern modification program to manage patellofemoral pain in runners.

! CASE DESCRIPTION: Three female runners with unilateral patellofemoral pain who initially presented with a rearfoot strike pattern underwent 8 sessions of landing pattern modification program using real-time audio feedback from a force sensor placed within the shoe. Ground reaction forces during running were assessed with an instru-mented treadmill. Patellofemoral pain symptoms were assessed using 2 validated questionnaires. Finally, running performance was measured by self-reported best time to complete a 10-km run in the previous month. The runners were assessed before, immediately after, and 3

months following training.

! OUTCOMES: The landing pattern of runners was successfully changed from a rearfoot to a non-rearfoot strike pattern after training. This new pat-tern was maintained 3 months after the program. The vertical impact peak and rates of loading were shown to be reduced. Likewise, the symptoms related to patellofemoral pain and associated functional limitations were improved. However, only 1 of the participants reported improved running performance after the training.

! DISCUSSION: This case series provided preliminary data to support further investigation of interventions leading to landing pattern modification in runners with patellofemoral pain.

! LEVEL OF EVIDENCE: Therapy, level 4. J Orthop Sports Phys Ther 2011;41(12):914-919, Epub 25 October 2011. doi:10.2519/jospt.2011.3771

! KEY WORDS: biofeedback, gait retraining, impact peak, impact rate, landing pattern

1Research Associate, Department of Rehabilitation Sciences, Hong Kong Polytechnic University, Hung Hom, Hong Kong, China; Postdoctoral Fellow, Department of Physical Medicine and Rehabilitation, Harvard Medical School, Harvard University, Cambridge, MA. 2Director, Spaulding National Running Center, Department of Physical Medicine and Rehabilitation, Harvard Medical School, Harvard University, Cambridge, MA. The experimental protocol of this study was reviewed and approved by The Ethics Review Committee of the Hong Kong Polytechnic University. Address correspondence to Dr Roy Cheung, Spaulding National Running Center, Department of Physical Medicine and Rehabilitation, Harvard Medical School, Harvard University, Cambridge, MA 02138. Email: [email protected]

ROY T.H. CHEUNG, PT, PhD1 • IRENE S. DAVIS, PT, PhD2

Landing Pattern Modification to Improve Patellofemoral Pain

in Runners: A Case Series

PFP. Through the linkage of the kine-matic chain, hip muscle weakness11,29 and excessive foot pronation20 have also been

proposed to lead to the development of PFP. Therefore, different treatment ap-proaches6,11 have been evaluated in the management of PFP.

Running is a popular sport worldwide. According to an epidemiological study,36 the overall annual rate of running injury ranges from 37% to 56%. The incidence rate, calculated according to running time, is between 2.5 to 12.1 injuries per 1000 hours of running, with the knee being the most vulnerable joint. Among those knee injuries, PFP is the most common condition. PFP in runners has been linked to abnormal lower extremity movement patterns4,22 and weaknesses of hip muscles.33 However, the role of abnormal kinetics in the development of PFP has not been fully examined. Verti-cal impact loading has been associated with a number of conditions, including plantar fasciitis,27 tibial stress fractures,28 and knee osteoarthritis.13,23 A recent pi-lot study suggested that runners with a history of PFP may exhibit a higher im-pact peak and loading rate than healthy runners.9

Approximately 75% of runners make initial contact with the ground using a rearfoot strike pattern (ie, they land on their heels).12 This rearfoot strike pattern results in a very distinct vertical impact peak, which may be eliminated or signifi-

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Original article

Br J Sports Med 2011;45:691–696. doi:10.1136/bjsm.2009.069112 691

Accepted 19 January 2010Published Online First 28 June 2010

ABSTRACT Background Patellofemoral pain syndrome (PFPS) is the most common overuse injury in runners. Recent research suggests that hip mechanics play a role in the development of this syndrome. Currently, there are no treatments that directly address the atypical mechanics associated with this injury. Objective The purpose of this study was to deter-mine whether gait retraining using real-time feedback improves hip mechanics and reduces pain in subjects with PFPS. Methods Ten runners with PFPS participated in this study. Real-time kinematic feedback of hip adduction (HADD) during stance was provided to the subjects as they ran on a treadmill. Subjects completed a total of eight training sessions. Feedback was gradually removed over the last four sessions. Variables of interest included peak HADD, hip internal rotation (HIR), contralateral pel-vic drop, as well as pain on a verbal analogue scale and the lower-extremity function index. We also assessed HADD, HIR and contralateral pelvic drop during a single leg squat. Comparisons of variables of interest were made between the initial, fi nal and 1-month follow-up visit. Results Following the gait retraining, there was a signifi cant reduction in HADD and contralateral pelvic drop while running. Although not statistically signifi cant, HIR decreased by 23% following gait retraining. The 18% reduction in HADD during a single leg squat was very close to signifi cant. There were also signifi cant improvements in pain and function. Subjects were able to maintain their improvements in running mechanics, pain and function at a 1-month follow-up. An unexpected benefi t of the retraining was an 18% and 20% reduc-tion in instantaneous and average vertical load rates, respectively. Conclusions Gait retraining in individuals with PFPS resulted in a signifi cant improvement of hip mechan-ics that was associated with a reduction in pain and improvements in function. These results suggest that interventions for PFPS should focus on addressing the underlying mechanics associated with this injury. The reduction in vertical load rates may be protective for the knee and reduce the risk for other running-related injuries.

INTRODUCTION Running is one of the most popular forms of exercise in the USA. Annually, 50–85% of runners will sustain an injury. 1 2 Of these injures, patell-ofemoral pain syndrome (PFPS) is the most com-monly reported. 3 PFPS often becomes chronic, with up to 91% of individuals reporting continued knee

pain 4–18 years after being initially diagnosed. 4 In addition, recent research suggests that having a history of PFPS increases the risk of later develop-ing patellofemoral osteoarthritis (OA). 5

The aetiology of PFPS is multifactorial in nature. Most investigators agree that PFPS is related, in part, to faulty lower-extremity mechanics. In particular, there is growing scientifi c support for the relationship between hip mechanics and patellofemoral joint mechanics. In an early cadav-eric study, Huberti et al reported that increasing the Q-angle (which would be associated with increased hip adduction (HADD)) resulted in greater contact pressure on the lateral aspect of the patella. 6 In a more recent cadaveric study, Li et al demonstrated that increasing femoral inter-nal rotation resulted in greater lateral patellar con-tact pressure. 7 Over time, the repetitive exposure to these motions may damage the cartilage and lead to greater stress on the highly innervated subchondral bone. 8 9

There is also emerging evidence that altered hip kinematics during dynamic activities are present in individuals with PFPS. For example, a recent study has found greater peak hip internal rotation (HIR) during running in individuals with PFPS. 10 In addition, Willson et al reported that individu-als with PFPS run, jump and squat with greater HADD compared with healthy controls. 11 They also found greater contralateral pelvic drop across activities. 11 Finally, a recent prospective study has found that runners who developed PFPS had greater HADD compared with their healthy counterparts. 12

Several investigators have examined the effect of hip abductor and external rotation strength-ening on PFPS. 13 14 While they have reported improvements in hip strength and reductions in knee pain, most have lacked any follow-up beyond the completion of the treatment. However, in a study by Blønd et al , it was reported that 80% of individuals who had engaged in a strengthening programme continued to have pain 5 years later. In addition, 74% had to reduce their physical activity as a result of pain. 15 This suggests that the underlying mechanics were not addressed directly.

There is increasing evidence that individuals can successfully alter their gait mechanics using real-time feedback. 16 – 18 19 As an example, White et al studied a group of individuals with a unilat-eral hip replacement and associated reduced load-ing on their involved side. 16 After 8 weeks of gait retraining using real-time force feedback from an

1 Division of Physical Therapy, University of Kentucky, Lexington, Kentucky, USA 2 University of Delaware, Newark, Delaware, USA

Correspondence to Dr Brian Noehren, Division of Physical Therapy, University of Kentucky, Wethington Bldg rm 204D, 900 S, Limestone Road, Lexington, KY 40536-0200, USA; [email protected]

The effect of real-time gait retraining on hip kinematics, pain and function in subjects with patellofemoral pain syndrome B Noehren, 1 J Scholz, 2 I Davis 2

06_bjsports69112.indd 69106_bjsports69112.indd 691 6/8/2011 9:28:14 PM6/8/2011 9:28:14 PM


OUTCOMES

• As a result of fatigue novice runners display changes in ...

trunk flexion and extension

hip extension

ankle pronation

• Trunk kinematics appear to be significantly affected during fatigued running and should not be overlooked

Koblbauer et al. JSAMS 2013


translating and transferring fundamental and efficacious evidence into practical prevention strategies

epidemiological (cost)effectiveness evidence leading to clinical / practical

guidelines

biomechanical and neurophysiological changes

practical & public health impact through high

compliance and proper use of effective measures

translating and transferring effectiveness evidence into biomechanical experiments unravelling the underlying

pathways by which measures prevent injury


MYTH OR REALITYDOES IT MATTER?

• Of course it matters, but the discussion seems to revolve around fundamental approaches

What is CS

Can we measure CS?

Which measures are affected by CS?

Is there a theoretical background to CS?

...


Myth or legend?It doesn’t matter to have this discussion on a fundamental level if there is no clinical effectiveness to support the practical use of CS


With current clinical knowledge CS appears to be a myth

Weak correlations between CS and performance measures

Weak predictive value of CS in regards to injury risk

Weak outcomes due to methodological issues?

Myth or legend?


With current clinical knowledge CS could become a legend

Posi8ve outcomes when CS is employed in LBP management

In novice or recrea8onal athletes there is room to CS improvement providing hooks for preven8on

Myth or legend?



Evert Verhagen

www.slhamsterdam.com

@evertverhagen

[email protected]


Core stability

Health & Medicine

effective vrijdag

individual vrijdag

wikipedia vrijdag

practical public health

clinical practical guidelines

aging public health

practical approaches

department of public