ACL INJURY PREVENTION - Jordan Strength · 2015-01-16 · PREVENTION ACL INJURY / RE-INJURY PREVENTION 2014-12-16 PhD Candidate, Faculty of Medical Science, University of Calgary
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IDENTIFYING RISK FACTORS AND PROGRAMMING FOR INJURY
PREVENTION
ACL INJURY / RE-INJURY PREVENTION
2014-12-16
PhD Candidate, Faculty of Medical Science, University of Calgary
Director of Strength and Conditioning, Canadian Sport Institute-Calgary
Director of Sport Science | Sport Medicine, Canadian Alpine Ski Team
MATT JORDAN, M.Sc., CSCS
PRESENTATION OVERVIEW
§ Identify modifiable (trainable) risk factors for ACL injury
§ Consequences of ACL injury
§ Programming for ACL injury / re-injury prevention
§ Female athletes at greater risk (4-6x male counterpart) (Arendt et al., 1995; Myer et al., 2009; Prodromos et al., 2008)
§ Non-contact injury occurs in transitional zones (i.e. deceleration of the BCM) (Beynnon et al., 1998)
§ Increased risk for non-contact ACL injury attributable to risky biomechanics and altered intermuscular coordination (Hewett et al., 2005; Zebis et al., 2009)
RELATIONSHIP B/W FUNCTIONAL ASYMMETRY AND MUSCLE ASYMMETRY
RE-INJURY CMJ CONCENTRIC PHASE SJ PHASE 2
STATUSCM
J EC
CEN
TRIC
DEC
EL P
HA
SE K
INET
IC IM
PULS
E A
SYM
MET
RY IN
DEX
(%)
0
5
10
ACL−R CONTROL
STATUSACL−RCONTROL
(Jordan et al., 2013)
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6
SJ LATE PHASE KI ASYMMETRY INDEX (%)
CM
J C
ON
CEN
TRIC
PH
ASE
KI A
SYM
MET
RY IN
DEX
(%)
0
5
10
15
−5 0 5 10 15 20 25
BADEXA02468
10
STATUSCOPERNON COPER
MUSCLE MASS AI
IDENTIFYING AT RISK SKIERS:KINETIC IMPULSE ASYMMETRY INDEX IDENTIFYING AT RISK ATHLETES
§ N = 71 athletes § Females: n=51, Age=20.6±2.3 years, Body Mass =
67.8±11.5 kg
§ Males: n=20, Age=20.1±1.7 years, Body Mass = 78.7±16.5 kg)
§ Alpine skiing, luge, soccer, rugby, wrestling
§ Assessed at the start of the off-season preparatory period and throughout training (1x/week)
ASY
MM
ETRY
IND
EX C
MJ
ECC
DEC
EL P
HA
SE (%
)
5
10
15
20
STATUSUNINJUREDINJURED
ASY
MM
ETRY
IND
EX C
MJ
ECC
DEC
EL P
HA
SE (%
)
5
10
15
20
STATUSUNINJUREDINJURED
IDENTIFYING PREVIOUSLY UNINJURED AT RISK ATHLETES
Odds of injury 1.2x (95% CI = 1.1-1.4x) (P<0.01)
ACL INJURIES 2010 – 2014 = NONE
ACL RE-INJURIES = NONE
LOWER BODY RE-INJURIES = 2
STRATEGIES FOR ACL INJURY/RE-INJURY PREVENTION
TRAINING CONSIDERATIONS
Can the system find the right solution?
Can the motor system generate the right solution?
WHERE IS THE BREAKDOWN?
(Aagaard, 2003; Sale, 2003)
282 mechanism for adaptation
For example, it has been estimated that in tricepsbrachii, only about 5% of the motor units areType IIb (IIx), but this small number of units contains about 20% of the total number of musclefibres in the muscle (Enoka & Fuglevand 2001).The second way increased activation could occuris through increased motor unit firing rates (Fig.15.3, middle panel). By increasing or decreasingfiring rate (also referred to as discharge rate orrate coding), a motor unit can vary its force out-put over an approximately 10-fold range, knownas the force–frequency relationship. The motorunit firing rates observed in maximal voluntarycontractions appear to be lower than needed formaximum force output (Enoka & Fuglevand2001; cf. Bellemare et al. 1983). Training mayallow for firing rates consistently high enough tobe on the plateau of the force–frequency relation-ship, where force is maximal. The third wayincreased activation could occur is also throughincreased motor unit firing rates (Fig. 15.3, bot-tom panel). When the intent is to contract themuscle as fast as possible with maximum rate offorce development (so-called ‘ballistic’ contrac-tions), motor units begin firing at a very high fre-quency, followed by a rapid decline in frequency(Zehr & Sale 1994). The peak firing rates attained
Fig. 15.1 Control of muscle by the nervous system.Voluntary strength performance is determined notonly by the quantity and quality of the involvedmuscle mass, the ‘engine’, but also by the ability of thenervous system, the engine controller, to effectivelyactivate the muscles. Nervous system adaptations tostrength training may improve the control of musclesto increase maximum force (strength). These ‘neural’adaptations may occur in higher brain centres orwithin the spinal cord.
Strength training
Neural adaptation
Appropriatesynergist activation
HAntagonistactivation
Agonistactivation
HForce and/or rate of force development
HStrength performance
Fig. 15.2 Neural adaptations to strength training may take the form of increased activation of agonistmuscles, more appropriate activation of synergistmuscles (‘coordination’), and decreased (relative)activation of antagonist muscles. These adaptationswould act to increase maximum force (strength)and/or rate of force development.