Increases in Intracellular Water Explain Strength and Power Improvements over a Season

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A. M. Silva, C. N. Matias, D. A. Santos, P. M. Rocha, C. S. Minderico, L. B. Sardinha

Increases in Intracellular Water Explain Strength and Power Improvements over a Season

Int J Sports MedDOI 10.1055/s-0034-1371839

0172-4622

Training & Testing

Silva AM et al. Increases in Intracellular Water … Int J Sports Med

accepted after revision January 23 , 2014

BibliographyDOI http://dx.doi.org/10.1055/s-0034-1371839Published online: 2014Int J Sports Med © Georg Thieme Verlag KG Stuttgart · New YorkISSN 0172-4622

Correspondence Analiza Mónica Silva Exercise and Health Laboratory CIPER Faculdade Motricidade Humana Universidade de Lisboa Estrada da Costa 1495-688 Cruz-Quebrada Portugal Tel.: + 35/121/4149 160 Fax: + 35/121/4149 193 [email protected]

Key words ● ▶ dilution techniques ● ▶ body composition ● ▶ athletic training ● ▶ water compartments ● ▶ dual energy x-ray

absorptiometry

Increases in Intracellular Water Explain Strength and Power Improvements over a Season

season. Signifi cant increases in maximal strength and power were observed in female basketball players during the competitive season, while no reported associations were observed over the season [ 5 ] . In addition to these unclear eff ects of body composition on performance during the season, few studies reported the infl uence of the major FFM component, total-body water (TBW) and its constituents, the extracellular (ECW) and the intracellular water (ICW) compartments, on performance [ 20 , 21 ] . These authors reported that judo athletes who reduced ICW decreased power and grip strength. Dual-energy x-ray absorptiometry (DXA) has emerged as an useful and valid method for body composition analysis in clinical and laboratory settings [ 11 ] . However, only a few studies used DXA to track changes in FM and FFM throughout the season [ 1 , 2 , 22 ] . Additionally a small number of studies accurately assessed changes in TBW and its compartments [ 20 , 21 ] . Therefore, the use of deuterium and bromide dilution techniques to accurately assess TBW and ECW, respectively, is

Introduction ▼ Changes in body composition and physical per-formance occur from the start to the end of a sports training and competitive season in basket-ball [ 19 , 22 ] , volleyball [ 1 , 2 ] and handball players [ 3 , 4 ] . For sustained vigorous off ensive and defen-sive maneuvers along with rapid and powerful movements, physical abilities are important for winning among basketball, volleyball and hand-ball players. Physical tests such as vertical jump and lower body strength production are com-monly used to assess the physical performance-related characteristics of these sports [ 2 – 5 ] . However, the studies conducted over the course of a season reporting the impact of body compo-sition changes on performance are scarce, mainly focused on fat mass (FM) and fat-free mass (FFM), and use body composition techniques of limited accuracy, such as anthropometry [ 2 – 5 ] . Changes in adiposity correlated positively with changes in maximal strength and muscle power in elite female [ 4 ] and male handball players [ 3 ] over a

Authors A. M. Silva , C. N. Matias , D. A. Santos , P. M. Rocha , C. S. Minderico , L. B. Sardinha

Affi liation Exercise and Health Laboratory, CIPER, Fac Motricidade Humana, Univ Lisboa, 1499-002 Cruz-Quebrada, Portugal

Abstract ▼ Changes in body components occur over a sea-son, but their impact on performance is still unclear. We aimed to analyze the relationship between changes in leg strength and jump per-formance with body composition over a sea-son in highly trained athletes. Measures from the beginning to the main competitive periods of a season were obtained in 40 male and 23 female basketball, handball and volleyball play-ers (20 ± 5 years) for fat (FM) and fat-free mass (FFM) estimated by DXA. Total body water (TBW) and extracellular water (ECW) were assessed by deuterium and bromide dilution, respectively, and intracellular water (ICW) was calculated as TBW minus ECW. Maximal strength was deter-

mined by the leg press, while jumping height was assessed with squat (SJ) and countermove-ment (CMJ) jumps. Signifi cant improvements in strength (12.5 ± 20.8 %) and jumping height (SJ:8.3 ± 13.9 %; CMJ:6.3 ± 8.5 %) were found. FFM, TBW and ECW signifi cantly increased (3.0 ± 2.7 %; 1.7 ± 5.5 %; 3.0 ± 8.6 %, respectively), while %FM decreased ( − 4.5 ± 9.1 %) and no changes were observed in ICW (1.2 ± 9.7 %). Among body com-position changes only ICW was associated with performance even adjusted for gender, age, season length and sport (strength: β = 71.209, p = 0.012; SJ: β = 0.311, p = 0.049; CMJ: β = 0.366, p = 0.018). Body composition, strength and jump-ing height improved over a season and ICW was the main predictor of performance in national level players.

Training & Testing

Silva AM et al. Increases in Intracellular Water … Int J Sports Med

relevant to understand the infl uence of water compartments on performance. In fact, the extent to which changes in body com-position, TBW and fl uid distribution determines strength and power in team sports, remains unclear. Therefore, the purpose of this study was to examine the rela-tionship between changes in strength and jumping performance over a season with TBW, water compartments, FM and FFM in national level basketball, handball and volleyball players.

Methods ▼ Participants and study design Forty males and twenty-three female basketball (19 males/14 females), handball (9 males) and volleyball players (12 males/9 females) with a mean age of 20 years and playing for teams com-peting in the Portuguese National Championships volunteered to participate in this study. Inclusion criteria were: 1) > 10 h training per week; 2) negative test outcomes for performance enhancing drugs; and 3) not taking any medications or dietary supplements. No females were taking oral contraceptives (self-reported) and those reporting a regular menstrual cycle were assessed during the luteal phase. All participants were informed about the possible risks of the investigation before giving their written informed consent to participate. The study was approved by the Ethics Committee of the Faculty of Human Kinetics, Uni-versity of Lisbon and conducted in accordance with the ethical standards of the International Journal of Sports Medicine [ 6 ] . This was an observational study with a follow-up over a season ranging from 6 to 8 months, depending on each sport’s competi-tive timetable. The fi rst period of evaluation was assessed at the beginning of the season, whereas the second period correspond-ing to the competitive-phase occurred just before the main stage of the competition. The athletes’ training regimens consisted of 5 sessions per week with a total of 2 h each, divided into techni-cal-tactical training (which included endurance running, drills with the ball in hand, sprint running and practice game). Special attention was also given to footwork exercises, jumping and running abilities, and hand-eye coordination. During the week-ends of the competitive period, the teams played at least one game integrated in the National Championships. Twice a week athletes performed resistance training for nearly 1 h prior to the sport practices. Afterwards, general resistance training pro-gressed from general conditioning (weeks 1–4), to hypertrophy (weeks 5–8) then to maximal strength and power (weeks 9–16) and concluded with specifi c strength training (weeks 17–32). In both periods body composition measurements were carried out in the morning following 12-h fasting with abstinence from caff eine or alcohol during the preceding 24-h and no vigorous exercise within 15 h, while physical tests were performed in the afternoon.

Body composition Each subject’s weight and height were measured with a scale and stadiometer to the nearest 0.01 kg and 0.1 cm, respectively, while wearing a bathing suit and without shoes (Seca, Hamburg, Germany). Body composition was assessed by DXA, a fan-beam densitom-eter, and using software QDR for windows version 12.4 (Hologic Explorer-W, Waltham, USA) with estimates of FM, FFM and lean soft-tissue (LST) as described elsewhere [ 22 ] .

Total body water was assessed by deuterium dilution using a Hydra stable isotope ratio mass spectrometer (PDZ, Europa Sci-entifi c, UK). Procedures are described in detail elsewhere [ 14 ] . Extracellular water was assessed by a sodium bromide (NaBr) dilution measured by high-performance liquid chromatography (Dionex Corporation, Sunnyvale, CA, USA). Procedures are described in detail elsewhere [ 14 ] . Intracellular water (ICW) was calculated as the diff erence between TBW and ECW using the dilution techniques men-tioned above.

Hydration status To assure that athletes were in an euhydrated state, urine spe-cifi c gravity (USG) was determined by a refractometer (Urisys 1100 Urine Analyzer, Roche, Portugal) [ 14 ] .

Dietary intake Food intake was assessed over a 7-day period using a 24-h diet records, at the beginning of the season and the competitive training period, as described elsewhere [ 22 ] .

Physical tests Physical tests were carried out in the afternoon following a standardized warm-up of 5 min on a stationary cycle ergometer at 50 W. Each player was previously familiarized with the proto-col and verbally encouraged to give maximum eff ort during the tests specifi ed below. Maximal isometric strength and maximal rate of force develop-ment were assessed on a leg press apparatus attached to a cus-tom contact platform (BioPlux System, version 1.0, Lisbon, Portugal). Before the test, all participants performed 2 practice trials with a rest period of 30 s between each repetition. The legs were kept parallel and placed on the machine platform, shoulder width apart, with knees at an angle of 110 °. The athletes were instructed to perform the maximal isometric contraction during 3 trials, with a rest period of 90 s, and the best result being recorded. A total of 62 athletes had complete data at both moments for this test. Explosive power of the lower limbs was assessed by performing 3 vertical-jumps. A squat jump (SJ) and countermovement jump (CMJ) were performed using a custom contact platform (BioPlux System, version 1.0, Lisbon, Portugal). Before jumping, all par-ticipants performed 2 trials, with a resting period of 15 s between jumps. The SJ was performed with the starting position of a squat (knees fl exed at an angle of ~100–110 ° and hands on the hips), while the CMJ started from an upright standing posi-tion. Athletes made a maximal vertical jump landing on the plat-form. Participants performed 3 jumps each and rested 30 s between trials and 2–3 min between the SJ and CMJ. The highest jumping height was noted. A total of 59 athletes had complete data at both moments for the squat jump, whereas a subsample of 38 athletes had complete data for the CMJ (12 basketball play-ers: 7 males and 5 females; 7 male handball players; and 19 vol-leyball players: 11 males and 8 females).

Statistical analysis Data were analyzed with SPSS Statistics for Windows Version 19.0, 2010 (SPSS Inc., IBM Company, Chicago, Illinois, USA). Changes were expressed as a percentage of the baseline value. Paired and independent sample t-tests were performed to com-pare means between moments and within groups while analysis of covariance was used to compare groups, adjusting for possible

Training & Testing

Silva AM et al. Increases in Intracellular Water … Int J Sports Med

confounders. Potential interactions of gender with body compo-sition changes in explaining each dependent variable were explored in separate models using multiple regression analysis. If interaction terms were not statistically signifi cant in explain-ing strength and jump height (p > 0.05), data were reported with both genders pooled. Statistical signifi cance was set at p < 0.05.

Results ▼ Subject characteristics, body composition and performance are presented in ● ▶ Table 1 . As observed in ● ▶ Table 1 , athletes signifi cantly increased weight, LST and FFM while relative values of FM decreased. TBW and ECW signifi cantly increased whereas, no changes were observed for ICW and USG. Participants signifi cantly increased leg strength, SJ height, and CMJ height, while no changes were observed for the rate of max-imal leg strength production. A total of 42 dietary records were completed at both moments, and no diff erences were observed with regard to energy intake (10 688 ± 2 508 kJ/day vs. 11 186 ± 2 500 kJ/day), protein (118 ± 35 g/day vs. 119 ± 35 g/day), carbohydrates (322 ± 81 g/day vs. 337 ± 78 g/day), fat (86 ± 24 g/day vs. 93 ± 24 g/day) or water intake (2223 ± 911 g/day vs. 2345 ± 971 g/day). The association between changes in body composition and strength and power revealed that only ICW was signifi cantly related to leg strength, SJ and CMJ heights ( ● ▶ Fig. 1 ), remaining signifi cant after adjusting for age, gender, season length and sport in leg strength (β = 71.209, p = 0.012), SJ height (β = 0.311, p = 0.049) and CMJ height (β = 0.366, p = 0.018).

Even though the mean value of changes in ICW from the begin-ning of the season (27.0 ± 6.7 kg) to the competitive period (27.2 ± 6.9 kg) was non-signifi cant, athletes who showed an increase in ICW also displayed improvements in leg strength and jumping height. In view of this result we categorized athletes into 2 groups according to their changes in strength and power during the season. Athletes with changes of less than 3 % or more than 3 % were categorized as group 1 or 2, respectively. ● ▶ Fig. 2 indicates signifi cant ICW diff erences between groups, adjusted for age, gender, season length and sport, with group 2 increasing ICW while group 1 decreased.

Discussion ▼ This study was the fi rst to track body composition estimated by DXA over a season, including TBW and its compartments by dilution techniques, along with leg strength and jumping height measures in highly trained basketball, handball and volleyball players. Overall, athletes signifi cantly decreased adiposity, maintained ICW and increased LST, TBW, ECW, maximal leg strength and jumping height. Studies using hydrostatic weighing have shown that basketball players lost FM and gained signifi cant amounts of FFM [ 19 ] while others observed no changes [ 9 ] or even a signifi cant FFM reduction in volleyball players [ 9 ] . Using anthropometric indica-tors (skinfolds), FM decreased and FFM increased over the sea-son in basketball players [ 12 ] and male handball players [ 3 ] . Our fi ndings showed a signifi cant improvement in jumping height and maximal leg strength from the beginning of the study to the competitive phase of the season, similar in magnitude to

Table 1 Body composition, TBW, water compartments, hydration status, strength and jumping height at the beginning of the season (BS), at the fi nal stage of the competitive period (FCP) and during changes* over the season.

BS FCP Changes BS FCP Changes BS FCP Changes

Males (n = 40) Females (n = 23) Total (n = 63)

age (years) 20.1 ± 5.0 20.7 ± 4.9 19.9 ± 5.6 20.4 ± 5.7 20.0 ± 5.2 20.5 ± 5.2 height (cm) 191.0 ± 8.7 191.3 ± 8.9 0.2 ± 0.4† 173.7 ± 8.1‡ 174.0 ± 8.1‡ 0.2 ± 0.3† 184.7 ± 11.9 185.0 ± 12.0 0.2 ± 0.4† body mass (kg) 83.4 ± 10.0 84.3 ± 9.5 1.3 ± 2.9† 64.5 ± 9.5‡ 66.2 ± 9.5‡ 2.7 ± 2.8† 76.5 ± 13.4 77.7 ± 12.9 1.8 ± 2.9† BMI (kg/m 2 ) 22.8 ± 2.1 23.0 ± 2.0 1.0 ± 2.9† 21.3 ± 2.3‡ 21.8 ± 2.0‡ 2.3 ± 3.2† 22.3 ± 2.3 22.6 ± 2.1 1.4 ± 3.1† FM ( %) 15.6 ± 4.0 14.8 ± 3.6 − 4.7 ± 10.9† 25.9 ± 4.9‡ 24.9 ± 5.0‡ − 4.2 ± 4.7† 19.3 ± 6.6 18.5 ± 6.4 − 4.5 ± 9.1† FM (kg) 13.0 ± 4.1 12.4 ± 3.7 − 3.1 ± 13.0 16.8 ± 4.7‡ 16.5 ± 4.7‡ − 2.0 ± 6.3 14.4 ± 4.7 13.9 ± 4.5 − 2.7 ± 10.9 TBW(kg) 52.1 ± 6.4 52.8 ± 5.8 1.8 ± 5.1† 34.7 ± 4.9‡ 35.1 ± 4.4‡ 1.6 ± 6.1 45.7 ± 10.3 46.4 ± 10.1 1.7 ± 5.5† ECW (kg) 21.0 ± 2.6 21.2 ± 2.4 1.6 ± 9.0 14.8 ± 1.9‡ 15.5 ± 2.1‡ 5.3 ± 7.6† 18.7 ± 3.8 19.1 ± 3.6 3.0± 8.6† FFM (kg) 69.8 ± 8.3 71.2 ± 8.1 2.5 ± 2.8† 47.4 ± 6.5‡ 49.1 ± 6.4‡ 3.7 ± 2.4† 61.6 ± 13.3 63.0 ± 13.1 3.0 ± 2.7† LST (kg) 66.4 ± 7.8 67.8 ± 7.7 2.5 ± 2.8† 45.0 ± 6.1‡ 46.7 ± 6.1‡ 3.9 ± 2.4† 58.6 ± 12.7 59.9 ± 12.5 3.0 ± 2.7† ICW (kg) 31.1 ± 4.4 31.6 ± 4.3 2.2 ± 8.3 19.9 ± 3.4‡ 19.6 ± 2.6‡ − 0.5 ± 11.8 27.0 ± 6.7 27.2 ± 6.9 1.2 ± 9.7 USG 1.021 ± 0.004 1.022 ± 0.003 0.068 ± 0.479 1.020 ± 0.006 1.018 ± 0.005‡ 0.095 ± 0.805 1.020 ± 0.005 1.020 ± 0.004 0.011 ± 0.611 max. strength LP (N)

3600 ± 964 4054 ± 1094 14.4 ± 19.1† 2600 ± 731‡ 2737 ± 587‡ 9.2 ± 23.7 3235 ± 1005 3573 ± 1133 12.5 ± 20.8†

rate max. strength LP (N/ms)

15.9 ± 6.3 16.6 ± 6.6 9.9 ± 36.3 11.7 ± 6.4‡ 11.5 ± 4.4‡ 6.8 ± 32.8 14.4 ± 6.6 14.7 ± 6.4 8.8 ± 34.8

SJ (cm)# 28.3 ± 6.2 31.2 ± 5.6 10.5 ± 13.6† 22.1 ± 3.7‡ 22.9 ± 3.9‡ 4.5 ± 13.9 26.0 ± 6.2 28.2 ± 6.5 8.3 ± 13.9† CMJ (cm)§ 33.8 ± 6.7 36.0 ± 6.1 7.3 ± 9.0† 25.1 ± 4.5‡ 26.0 ± 4.1‡ 4.2 ± 7.5 30.8 ± 7.3 32.6 ± 7.2 6.3 ± 8.5†

BMI, body mass index; FM, fat mass; FFM, Fat-free mass; LST, Lean soft-tissue; TBW, total body water; ECW, extracellular water; ICW, intracellular water; USG, urine specifi c gravity; Max, Maximal; LP, Leg Press, SJ, squat jump; CMJ, countermovement jump * Changes were expressed as the percentage ( %) diff erence between FCP and BS from the baseline value # Valid data at FCP for 37 males and 22 females; thus changes were calculated in participants with valid data at BS and FCP (N = 59) § Valid data at BS and FCP for 25 males and 13 females; thus changes were calculated in participants with valid data at BS and FCP (N = 38) † Signifi cantly diff erent between BS and FCP, p < 0.05 ‡ Signifi cantly diff erent between gender, p < 0.05

Training & Testing

Silva AM et al. Increases in Intracellular Water … Int J Sports Med

those observed by previous studies conducted among basketball [ 5 , 15 ] , handball [ 3 , 13 ] and volleyball players [ 2 , 17 , 18 ] . Research is lacking concerning the impact of a season on FFM components, specifi cally TBW and the compartments thereof. In this regard, an important fi nding of our study was the link between improvements in leg strength and jumping height with ICW, the only body component whose changes aff ected per-formance irrespective of age, gender, season length, and sport.

The association between ICW (but no other body component) with maximal grip strength and upper-body power has been recently pointed out [ 20 , 21 ] using dilution techniques in judo athletes from a period of weight stability to the time prior to competition. Our study extends these fi ndings to team sports over the course of a season. While the justifi cation for these fi ndings needs further investi-gation, we advanced “The Cell Swelling Theory” as a potential

3000 r=0.303; p=0.016

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Fig. 1 Associations between intracellular water (ICW) diff erences observed over a season with lower-body maximal strength (N = 63) from the leg press test (upper panel), and height diff erences obtained during the squat jump (N = 59) and the countermovement jump (N = 38) (lower panels), including the whole-sample. The r-value repre-sents the coeffi cient of correlation.

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Increased less than 3% Increased more than 3%

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Fig. 2 Intracellular water (ICW) diff erences between athletes that improved less or more than 3 % of lower-body maximal strength (N = 14, N = 49, respectively), squat jump (SJ) maximal height (N = 22, N = 37, respectively), and counter-movement jump (CMJ) maximal height (N = 11, N = 27, respectively). Mean and standard error values are adjusted for age, gender, season length, and sport.

Training & Testing

Silva AM et al. Increases in Intracellular Water … Int J Sports Med

mechanism. This theory claims that cellular volume is a key sig-nal for the metabolic orientation of cell metabolism, specifi cally that cellular swelling leads to anabolism, whereas cellular shrinkage promotes catabolism [ 7 , 10 ] . In fact, even though mean ICW did not change, those players who increased the ICW pool increased strength and jumping performance meaning that this ICW expansion may have acted as an anabolic signal. Early investigations pointed out that 3–4 g of water is bound to each gram of glycogen [ 16 ] , which in turn will increase ICW. Athletes who gained ICW perhaps had an adequate fl uid and food intake to rapidly replenish glycogen stores, specifi cally within 2 h after exercise training [ 8 ] . Some of the strengths of this study included the longitudinal approach and the unique characteristics of the sample, basket-ball, handball and volleyball athletes from teams that were com-peting for the National Championship. State-of-the-art methods, such as dilution techniques, were uniquely employed to assess TBW, ECW, and ICW and DXA was used to assess body composi-tion. Lastly, athletes were evaluated during well-defi ned periods and reference values for body composition changes over the training process are provided. It is important to underscore that since athletes were tested at the beginning and at the main stage of the competitive period it is not known if these 2 measure-ments represent what happened during the entire season. In particular for handball players, the sample was not well bal-anced in number and gender as only 9 males participated in this study, thus compromising the generalization of these fi ndings for the female population. Additionally, these team results are not position-specifi c and do not account for likely variations that exist within each sport team.

Conclusion ▼ This observational study with a follow-up of national level hand-ball, basketball and volleyball players from the beginning to the main stage of a season point out signifi cant improvements in leg strength and jumping height. Decreases in %FM and increases in FFM, TBW and ECW were observed. Though no mean changes were found in ICW, this was the only component associated with leg strength and jumping height over the season. In fact, those athletes that increased ICW improved performance.

Acknowledgements ▼ We would like to express our gratitude to the athletes for their time and eff ort. This work was supported by the Portuguese Foundation for Science and Technology (Grant: PTDC/DES/098963/2008).

Confl ict of interest: The authors have no confl ict of interest to declare.

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