Article

Effects of acute dehydration and starvation on muscular strength and endurance

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Abstract

Maximal isometric muscular strength of elbow flexion, shoulder extension and knee extension (cable tensiometer) and muscular endurance (ergometer tolerance at 1,400 kpm/min and timed sit ups) were measured in 21 men, ages 21-30, before and after a 3 day experimental period. One group served as ad libitum control, the second underwent water restriction of 1,066 ml/day and the third group had no food or water (total starvation). A controlled, high protein diet (2,887 kcal/day) was utilized to accentuate urinary water loss. Mean total body wt decreased 5.7% (P < 0.05) in the dehydration group (DG), 5.8% (P < 0.05) in the starvation group (SG) and 1.5% (n.s.) in the control group (CG). Mean body strength losses were: control, 7.5%, dehydration 10.4% and starvation, 9.7%. Mean left elbow flexion strength was reduced 13.4% (P < 0.05) in the (CG) and 16.6% (P < 0.05) with starvation. Endurance to sit ups decreased 9% (P < 0.05) with (D) and 13% (P < 0.05) with (S). The dehydration and starvation states could be distinguished from control by similar increases in serum creatinine, urinary K and urinary osmolarity; and decreases in body wt, plasma vol, urinary min vol, and creatinine clearance. Changes unique to (S) were increased urinary creatinine, decreased serum glucose and decreased urinary Cl. Only elevated serum osmolarity with (D) separated it from (S) and (C). With (D), the decreased strength and endurance is attributed to water loss and electrolyte shifts. The greater loss of strength and endurance with (S) is attributed to water and electrolyte losses, especially K, plus the reduction in serum glucose concentration.

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... M uscular strength and power are considered a basic component of physical performance and the factors affecting strength have been studied intensively (3,5,6,11,18,21,24,26,36). The effects of water depletion on physical performance have been well established; however, a lack of experimental evidence exists concerning the effects of dehydration on anaerobic muscular power. ...
... Investigators have studied the detrimental effects of hypohydration (5,6,8,11,12,15,16,18,24,36,38) and the clinical manifestations of passively or actively induced hyperthermia (15,21,25,26,31,33) on exercise performance; however, discrepancies exist in the current research on dehydration and the effects it has on muscular strength and power. No significant differences between dehydrated ($4% body mass loss) and euhydrated (normally hydrated) conditions have been demonstrated for peak torque during a maximal isometric voluntary contraction or for time to fatigue for knee extensors and elbow flexors (18). ...
... Muscular performance due to dehydration has been demonstrated (5,22,38) with conflicting results. While dehydration has not been demonstrated to alter anaerobic exercise performance or postexercise blood lactate values (23), a 21% decrease in anaerobic power and a 10% decrease in anaerobic capacity has been demonstrated in dehydrated (5% of body mass) subjects (38). ...
Article
We examined the effects of active dehydration by exercise in a hot, humid environment on anaerobic muscular power using a test-retest (euhydrated and dehydrated) design. Seven subjects (age, 27.1 +/- 4.6 years; mass, 86.4 +/- 9.5 kg) performed upper and lower body Wingate anaerobic tests prior to and after a 1.5-hour recovery from a heat stress trial of treadmill exercise in a hot, humid environment (33.1 +/- 3.1C = 55.1 +/- 8.9% relative humidity) until a 3.1 +/- 0.3% body mass loss was achieved. Dehydration was confirmed by a significant body mass loss (P < 0.001), urine color increase (P = 0.004), and urine specific gravity increase (P = 0.041). Motivation ratings were not significantly different (P = 0.059), and fatigue severity was significantly (P = 0.009) increased 70% in the dehydrated compared to the euhydrated condition. Compared to the euhydrated condition, the dehydrated condition mean power was significantly (P = 0.014) decreased 7.17% in the upper body and 19.20% in the lower body. Compared to the euhydrated condition, the dehydrated condition peak power was significantly (P = 0.013) decreased 14.48% in the upper body and 18.36% in the lower body. No significant differences between the euhydrated and dehydrated conditions were found for decrease in power output (P = 0.219, power = 0.213). Our findings suggest that dehydration of 2.9% body mass decreases the ability to generate upper and lower body anaerobic power. Coaches and athletes must understand that sports performance requiring anaerobic strength and power can be impaired by inadequate hydration and may contribute to increased susceptibility to musculoskeletal injury.
... Of these, 28 [7, 8, 11-14, 17-20, 24, 25, 30-45] met all of the inclusion criteria, thereby producing a total of 85 individual studies and weighted mean treatment effects to investigate the impact of hypohydration on upper (6/85) and lower (10/85) body muscle endurance, upper (14/85) and lower (25/85) body muscle strength, muscle anaerobic power (9/85) and capacity (9/85), and vertical jumping ability (12/85). A total of 20 research manuscripts produced more than one weighted mean treatment effect, with Hayes and Morse [25] producing ten, Ftaiti et al. [34] producing two, Wilson et al. [45] two, Cheuvront et al. [17] two, Bigard et al. [8] two, Bijlani and Sharma [30] two, Bosco et al. [31] two, Bosco et al. [32] six, Caterisano et al. [33] three, Greiwe et al. [35] four, Gutierrez et al. [36] six, Jacobs [37] six, Jones et al. [13] two, Judelson et al. [11] six, Kraft et al. [38] two, Montain et al. [39] two, Naharudin and Yusof [40] six, Periard et al. [41] four, Viitasalo et al. [44] four, and Webster et al. [12] four effect estimates. The work of Naharudin and Yusof [40] and Caterisano et al. [33] contained three different groups of participants, while that of Gutierrez et al. [36] contained two different groups of participants. ...
... A total of 284 individuals are represented in the 28 research manuscripts retained for the present analysis. Of these, 129 were considered trained [11, 12, 18, 24, 32-34, 36, 37, 40-42, 44] and 155 untrained [7,8,13,14,17,19,20,25,30,31,33,35,38,39,43,45]. Their physical characteristics are presented in Table 2. Percent body fat mass and maximal oxygen consumption were reported in too few studies for their means to accurately represent the study sample and, therefore, are not reported. ...
... Of the 28 articles retained for analysis, hypohydration was induced via heat exposure in ten [8, 17, 33, 35-38, 40, 42, 44], via exercise plus heat exposure in ten [13,14,18,19,24,25,30,39,41,43], via exercise in a sweat suit in two [34,45], and via fluid restriction in six [7,11,12,20,31,32]. Although Webster et al. [12] used exercise in a sweat suit and Judelson et al. [11] used exercise plus heat exposure to dehydrate participants, the dehydration mode was All studies except that by Bosco et al. [31] provided the percent change in BW (i.e., hypohydration level). ...
Article
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BACKGROUND: How hypohydration impacts non-bodyweight (BW)-dependent muscle performance and vertical jumping ability remains to be determined using meta-analytic procedures. OBJECTIVES: Our objective was to determine the impact of hypohydration on muscle endurance, strength, anaerobic power and capacity and vertical jumping ability using a meta-analytic approach. DATA SOURCES: Studies were located using database searches and cross-referencing. SYNTHESIS METHODS: Effect summaries were obtained using random-effects models; method of moments mixed-effects analysis-of-variance-like procedures were used to determine differences between groups; and restricted maximum likelihood random-effects meta-regressions were performed to determine relationships between variables, impact of confounders, and interaction effects. RESULTS: A total of 28 manuscripts met the inclusion criteria, producing six (upper body muscle endurance), ten (lower body muscle endurance), 14 (upper body muscle strength), 25 (lower body muscle strength), nine (muscle anaerobic power), nine (muscle anaerobic capacity), and 12 (vertical jumping ability) effect estimates. Hypohydration impaired overall muscle endurance by 8.3 ± 2.3 % (P < 0.05), with no significant difference between upper body (-8.4 ± 3.3 %) and lower body (-8.2 ± 3.2 %). As a whole, muscle strength fell by 5.5 ± 1.0 % (P < 0.05) with hypohydration; the difference between lower (-3.7 ± 1.8 %) and upper (-6.2 ± 1.1 %) body was non-significant. Anaerobic power (-5.8 ± 2.3 %) was significantly altered with hypohydration, but anaerobic capacity (-3.5 ± 2.3 %) and vertical jumping ability (0.9 ± 0.7 %) were not. No significant correlations were observed between the changes in any of the muscle performance variables or vertical jumping ability and the changes in hypohydration level. Using an active procedure to dehydrate participants decreased muscle performance by an additional 5.4 ± 1.9 % (2.76-fold) (P = 0.02) compared with using a passive dehydration procedure. Trained individuals demonstrated a 3.3 ± 1.7 % (1.76-fold) (P = 0.06) lesser decrease in muscle performance with hypohydration than did untrained individuals. CONCLUSION: Hypohydration, or factors associated with dehydration, are likely to be associated with practically important decrements in muscle endurance, strength, and anaerobic power and capacity. However, their impact on non-BW-dependent muscle performance is substantially mitigated in trained individuals or when hypohydration is induced passively. Conversely, it is possible that body water loss (~3 % BW) may improve performance in BW-dependent tasks such as vertical jumping ability.
... One problem in describing the effects of dehydration relative to anaerobic performance is exercise mode variations. Tests of anaerobic performance include the vertical jump Gutierrez, Mesa, Ruiz, Chirosa, & Castillo, 2003;Hayes & Morse, 2010;Hoffman, Stavsky, & Falk, 1995;Judelson, Maresh, Farrell et al., 2007;Viitasalo, Kyrolainen, Bosco, & Alen, 1987;Watson et al., 2005), 10-s maximal cycle sprints (Yoshida et al., 2002), 30-s Wingate Anaerobic Tests (Jacobs, 1980), 50-, 100-, 200-, and 400-m sprints (Watson et al., 2005), Margaria power tests (Szygula & Jurczak, 1993), 1 repetition maximum (1-RM) weight lifting (Schoffstall, Branch, Leutholtz, & Swain, 2001), maximal static contractions (Ahlman & Karvonen, 1961;Bigard et al., 2001;Bijilani & Sharma, 1980;Bosco, Greenleaf, Bernauer, & Card, 1974;Evetovich et al., 2002;Ftaiti, Grelot, Coudreuse, & Nicol, 2001;Greenleaf, Prange, & Averkin, 1967;Greiwe, Staffey, Melrose, Narve, & Knowlton, 1998;Gutierrez et al., 2003;Hayes & Morse 2010;Montain et al., 1998;Saltin, 1964;Viitasalo et al., 1987), isokinetic force production (Hayes & Morse 2010;Moore et al., 1992), multiset resistance exercise (Judelson, Maresh, Farrell et al., 2007;Kraft et al., 2010), and both sprint (Schmidt, Corrigan, & Melby, 1990) and force production tests to exhaustion (Bijilani & Sharma, 1980;Bosco et al., 1974;Caterisano, Camaione, Murphy, & Gonino, 1988;Ftaiti et al., 2001;Griewe et al., 1998;Moore et al., 1992;Torranin, Smith, & Byrd, 1979). While all these exercise modes are dominated by anaerobic pathways, inherent differences exist (i.e., duration, active muscle volume, specific joint actions, and skill requirements). ...
... One problem in describing the effects of dehydration relative to anaerobic performance is exercise mode variations. Tests of anaerobic performance include the vertical jump Gutierrez, Mesa, Ruiz, Chirosa, & Castillo, 2003;Hayes & Morse, 2010;Hoffman, Stavsky, & Falk, 1995;Judelson, Maresh, Farrell et al., 2007;Viitasalo, Kyrolainen, Bosco, & Alen, 1987;Watson et al., 2005), 10-s maximal cycle sprints (Yoshida et al., 2002), 30-s Wingate Anaerobic Tests (Jacobs, 1980), 50-, 100-, 200-, and 400-m sprints (Watson et al., 2005), Margaria power tests (Szygula & Jurczak, 1993), 1 repetition maximum (1-RM) weight lifting (Schoffstall, Branch, Leutholtz, & Swain, 2001), maximal static contractions (Ahlman & Karvonen, 1961;Bigard et al., 2001;Bijilani & Sharma, 1980;Bosco, Greenleaf, Bernauer, & Card, 1974;Evetovich et al., 2002;Ftaiti, Grelot, Coudreuse, & Nicol, 2001;Greenleaf, Prange, & Averkin, 1967;Greiwe, Staffey, Melrose, Narve, & Knowlton, 1998;Gutierrez et al., 2003;Hayes & Morse 2010;Montain et al., 1998;Saltin, 1964;Viitasalo et al., 1987), isokinetic force production (Hayes & Morse 2010;Moore et al., 1992), multiset resistance exercise (Judelson, Maresh, Farrell et al., 2007;Kraft et al., 2010), and both sprint (Schmidt, Corrigan, & Melby, 1990) and force production tests to exhaustion (Bijilani & Sharma, 1980;Bosco et al., 1974;Caterisano, Camaione, Murphy, & Gonino, 1988;Ftaiti et al., 2001;Griewe et al., 1998;Moore et al., 1992;Torranin, Smith, & Byrd, 1979). While all these exercise modes are dominated by anaerobic pathways, inherent differences exist (i.e., duration, active muscle volume, specific joint actions, and skill requirements). ...
... Therefore, caution should be used when interpreting this as a true measure of anaerobic performance. Torranin et al. (1979) likewise reported a significant decrease in muscular endurance measured by the ability to maintain 75% of maximal voluntary contraction (~ 40 s) after dehydration by 4% via sauna, while Bosco et al. (1974) reported a 9% decrease in muscular endurance (2 min timed sit-up test) after a 5.7% reduction in body mass. Again, increased exercise duration, which magnifies reliance on aerobic (vs. ...
Article
This study examined effects of dehydration on a full body resistance exercise workout. Ten males completed two trials: heat exposed (with 100% fluid replacement) (HE) and dehydration (approximately 3% body mass loss with no fluid replacement) (DEHY) achieved via hot water bath (approximately 39 degrees C). Following HE and DEHY, participants performed three sets to failure (using predetermined 12 repetition maximum) of bench press, lat pull down, overhead press, barbell curl, triceps press, and leg press with a 2-min recovery between each set and 2 min between exercises. A paired t test showed total repetitions (all sets combined) were significantly lower for DEHY: (144.1 +/- 26.6 repetitions) versus HE: (169.4 +/- 29.1 repetitions). ANOVAs showed significantly lower repetitions (approximately 1-2 repetitions on average) per exercise for DEHY versus HE (all exercises). Pre-set rate of perceived exertion (RPE) and pre-set heart rate (HR) were significantly higher [approximately 0.6-1.1 units on average in triceps press, leg press, and approached significance in lat pull down (P = 0.14) and approximately 6-13 b min(-1) on average in bench press, lat pull down, triceps press, and approached significance for overhead press (P = 0.10)] in DEHY versus HE. Session RPE difference approached significance (DEHY: 8.6 +/- 1.9, HE: 7.4 +/- 2.3) (P = 0.12). Recovery HR was significantly higher for DEHY (116 +/- 15 b min(-1)) versus HE (105 +/- 13 b min(-1)). Dehydration (approximately 3%) impaired resistance exercise performance, decreased repetitions, increased perceived exertion, and hindered HR recovery. Results highlight the importance of adequate hydration during full body resistance exercise sessions.
... One problem in describing the effects of dehydration relative to anaerobic performance is exercise mode variations. Tests of anaerobic performance include the vertical jump Gutierrez, Mesa, Ruiz, Chirosa, & Castillo, 2003;Hayes & Morse, 2010;Hoffman, Stavsky, & Falk, 1995;Judelson, Maresh, Farrell et al., 2007;Viitasalo, Kyrolainen, Bosco, & Alen, 1987;Watson et al., 2005), 10-s maximal cycle sprints (Yoshida et al., 2002), 30-s Wingate Anaerobic Tests (Jacobs, 1980), 50-, 100-, 200-, and 400-m sprints (Watson et al., 2005), Margaria power tests (Szygula & Jurczak, 1993), 1 repetition maximum (1-RM) weight lifting (Schoffstall, Branch, Leutholtz, & Swain, 2001), maximal static contractions (Ahlman & Karvonen, 1961;Bigard et al., 2001;Bijilani & Sharma, 1980;Bosco, Greenleaf, Bernauer, & Card, 1974;Evetovich et al., 2002;Ftaiti, Grelot, Coudreuse, & Nicol, 2001;Greenleaf, Prange, & Averkin, 1967;Greiwe, Staffey, Melrose, Narve, & Knowlton, 1998;Gutierrez et al., 2003;Hayes & Morse 2010;Montain et al., 1998;Saltin, 1964;Viitasalo et al., 1987), isokinetic force production (Hayes & Morse 2010;Moore et al., 1992), multiset resistance exercise (Judelson, Maresh, Farrell et al., 2007;Kraft et al., 2010), and both sprint (Schmidt, Corrigan, & Melby, 1990) and force production tests to exhaustion (Bijilani & Sharma, 1980;Bosco et al., 1974;Caterisano, Camaione, Murphy, & Gonino, 1988;Ftaiti et al., 2001;Griewe et al., 1998;Moore et al., 1992;Torranin, Smith, & Byrd, 1979). While all these exercise modes are dominated by anaerobic pathways, inherent differences exist (i.e., duration, active muscle volume, specific joint actions, and skill requirements). ...
... One problem in describing the effects of dehydration relative to anaerobic performance is exercise mode variations. Tests of anaerobic performance include the vertical jump Gutierrez, Mesa, Ruiz, Chirosa, & Castillo, 2003;Hayes & Morse, 2010;Hoffman, Stavsky, & Falk, 1995;Judelson, Maresh, Farrell et al., 2007;Viitasalo, Kyrolainen, Bosco, & Alen, 1987;Watson et al., 2005), 10-s maximal cycle sprints (Yoshida et al., 2002), 30-s Wingate Anaerobic Tests (Jacobs, 1980), 50-, 100-, 200-, and 400-m sprints (Watson et al., 2005), Margaria power tests (Szygula & Jurczak, 1993), 1 repetition maximum (1-RM) weight lifting (Schoffstall, Branch, Leutholtz, & Swain, 2001), maximal static contractions (Ahlman & Karvonen, 1961;Bigard et al., 2001;Bijilani & Sharma, 1980;Bosco, Greenleaf, Bernauer, & Card, 1974;Evetovich et al., 2002;Ftaiti, Grelot, Coudreuse, & Nicol, 2001;Greenleaf, Prange, & Averkin, 1967;Greiwe, Staffey, Melrose, Narve, & Knowlton, 1998;Gutierrez et al., 2003;Hayes & Morse 2010;Montain et al., 1998;Saltin, 1964;Viitasalo et al., 1987), isokinetic force production (Hayes & Morse 2010;Moore et al., 1992), multiset resistance exercise (Judelson, Maresh, Farrell et al., 2007;Kraft et al., 2010), and both sprint (Schmidt, Corrigan, & Melby, 1990) and force production tests to exhaustion (Bijilani & Sharma, 1980;Bosco et al., 1974;Caterisano, Camaione, Murphy, & Gonino, 1988;Ftaiti et al., 2001;Griewe et al., 1998;Moore et al., 1992;Torranin, Smith, & Byrd, 1979). While all these exercise modes are dominated by anaerobic pathways, inherent differences exist (i.e., duration, active muscle volume, specific joint actions, and skill requirements). ...
... Therefore, caution should be used when interpreting this as a true measure of anaerobic performance. Torranin et al. (1979) likewise reported a significant decrease in muscular endurance measured by the ability to maintain 75% of maximal voluntary contraction (~ 40 s) after dehydration by 4% via sauna, while Bosco et al. (1974) reported a 9% decrease in muscular endurance (2 min timed sit-up test) after a 5.7% reduction in body mass. Again, increased exercise duration, which magnifies reliance on aerobic (vs. ...
Article
This review examines the influence of dehydration on muscular strength and endurance and on single and repeated anaerobic sprint bouts. Describing hydration effects on anaerobic performance is difficult because various exercise modes are dominated by anaerobic energy pathways, but still contain inherent physiological differences. The critical level of water deficit (approximately 3-4%; mode dependent) affecting anaerobic performance is larger than the deficit (approximately 2%) impairing endurance performance. A critical performance-duration component (> 30 s) may also exist. Moderate dehydration (approximately 3% body weight; precise threshold depends on work/recovery ratio) impairs repeated anaerobic bouts, which place an increased demand on aerobic metabolism. Interactions between dehydration level, dehydration mode, testing mode, performance duration, and work/recovery ratio during repeated bouts make the dehydration threshold influencing anaerobic performance mode dependent.
... One problem in describing the effects of dehydration relative to anaerobic performance is exercise mode variations. Tests of anaerobic performance include the vertical jump Gutierrez, Mesa, Ruiz, Chirosa, & Castillo, 2003;Hayes & Morse, 2010;Hoffman, Stavsky, & Falk, 1995;Judelson, Maresh, Farrell et al., 2007;Viitasalo, Kyrolainen, Bosco, & Alen, 1987;Watson et al., 2005), 10-s maximal cycle sprints (Yoshida et al., 2002), 30-s Wingate Anaerobic Tests (Jacobs, 1980), 50-, 100-, 200-, and 400-m sprints (Watson et al., 2005), Margaria power tests (Szygula & Jurczak, 1993), 1 repetition maximum (1-RM) weight lifting (Schoffstall, Branch, Leutholtz, & Swain, 2001), maximal static contractions (Ahlman & Karvonen, 1961;Bigard et al., 2001;Bijilani & Sharma, 1980;Bosco, Greenleaf, Bernauer, & Card, 1974;Evetovich et al., 2002;Ftaiti, Grelot, Coudreuse, & Nicol, 2001;Greenleaf, Prange, & Averkin, 1967;Greiwe, Staffey, Melrose, Narve, & Knowlton, 1998;Gutierrez et al., 2003;Hayes & Morse 2010;Montain et al., 1998;Saltin, 1964;Viitasalo et al., 1987), isokinetic force production (Hayes & Morse 2010;Moore et al., 1992), multiset resistance exercise (Judelson, Maresh, Farrell et al., 2007;Kraft et al., 2010), and both sprint (Schmidt, Corrigan, & Melby, 1990) and force production tests to exhaustion (Bijilani & Sharma, 1980;Bosco et al., 1974;Caterisano, Camaione, Murphy, & Gonino, 1988;Ftaiti et al., 2001;Griewe et al., 1998;Moore et al., 1992;Torranin, Smith, & Byrd, 1979). While all these exercise modes are dominated by anaerobic pathways, inherent differences exist (i.e., duration, active muscle volume, specific joint actions, and skill requirements). ...
... One problem in describing the effects of dehydration relative to anaerobic performance is exercise mode variations. Tests of anaerobic performance include the vertical jump Gutierrez, Mesa, Ruiz, Chirosa, & Castillo, 2003;Hayes & Morse, 2010;Hoffman, Stavsky, & Falk, 1995;Judelson, Maresh, Farrell et al., 2007;Viitasalo, Kyrolainen, Bosco, & Alen, 1987;Watson et al., 2005), 10-s maximal cycle sprints (Yoshida et al., 2002), 30-s Wingate Anaerobic Tests (Jacobs, 1980), 50-, 100-, 200-, and 400-m sprints (Watson et al., 2005), Margaria power tests (Szygula & Jurczak, 1993), 1 repetition maximum (1-RM) weight lifting (Schoffstall, Branch, Leutholtz, & Swain, 2001), maximal static contractions (Ahlman & Karvonen, 1961;Bigard et al., 2001;Bijilani & Sharma, 1980;Bosco, Greenleaf, Bernauer, & Card, 1974;Evetovich et al., 2002;Ftaiti, Grelot, Coudreuse, & Nicol, 2001;Greenleaf, Prange, & Averkin, 1967;Greiwe, Staffey, Melrose, Narve, & Knowlton, 1998;Gutierrez et al., 2003;Hayes & Morse 2010;Montain et al., 1998;Saltin, 1964;Viitasalo et al., 1987), isokinetic force production (Hayes & Morse 2010;Moore et al., 1992), multiset resistance exercise (Judelson, Maresh, Farrell et al., 2007;Kraft et al., 2010), and both sprint (Schmidt, Corrigan, & Melby, 1990) and force production tests to exhaustion (Bijilani & Sharma, 1980;Bosco et al., 1974;Caterisano, Camaione, Murphy, & Gonino, 1988;Ftaiti et al., 2001;Griewe et al., 1998;Moore et al., 1992;Torranin, Smith, & Byrd, 1979). While all these exercise modes are dominated by anaerobic pathways, inherent differences exist (i.e., duration, active muscle volume, specific joint actions, and skill requirements). ...
... Therefore, caution should be used when interpreting this as a true measure of anaerobic performance. Torranin et al. (1979) likewise reported a significant decrease in muscular endurance measured by the ability to maintain 75% of maximal voluntary contraction (~ 40 s) after dehydration by 4% via sauna, while Bosco et al. (1974) reported a 9% decrease in muscular endurance (2 min timed sit-up test) after a 5.7% reduction in body mass. Again, increased exercise duration, which magnifies reliance on aerobic (vs. ...
Article
This review examines the influence of dehydration on muscular strength and endurance and on single and repeated anaerobic sprint bouts. Describing hydration effects on anaerobic performance is difficult because various exercise modes are dominated by anaerobic energy pathways, but still contain inherent physiological differences. The critical level of water deficit (∼ 3–4%; mode dependent) affecting anaerobic performance is larger than the deficit (∼ 2%) impairing endurance performance. A critical performance-duration component (> 30 s) may also exist. Moderate dehydration (> 3% body weight; precise threshold depends on work/recovery ratio) impairs repeated anaerobic bouts, which place an increased demand on aerobic metabolism. Interactions between dehydration level, dehydration mode, testing mode, performance duration, and work/recovery ratio during repeated bouts make the dehydration thresh-old influencing anaerobic performance mode dependent. © 2012 by the American Alliance for Health, Physical Education, Recreation and Dance.
... With regard to neuromuscular function, con¯icting results have been reported in the case of dehydration as well as following passive heat exposure. Following dehydration, muscle strength and/or endurance capacity may either decrease (Bosco et al. 1968(Bosco et al. , 1974Houston et al. 1981;Torranin et al. 1979;Viitasalo et al. 1987), increase (Ahlman and Karvonen 1961;Widerman and Hagan 1982), or remain unchanged (Greiwe et al. 1998;Saltin 1964;Serfass et al. 1984;Singer and Weiss 1968). ...
... 100% corresponds to the maximal EMG value recorded in isometric conditions during the control session. *P < 0.05, **P < 0.01 for the pre-post fatigue comparison The present 12%±17% force decrements observed for the knee extension movement in isometric and isokinetic tests at the slowest velocity (Fig. 3) are consistent with earlier reports showing that dehydration (Bosco et al. 1968(Bosco et al. , 1974 and/or a rise in muscle temperature (Edwards 1983;Viitasalo et al. 1987) may impair the maximal capacity of force production in both isometric and dynamic conditions. In the case of moderate dehydration (less than 3% of BML), Bosco et al. (1968) reported similar (10%), but very variable reductions in maximal isometric strength among muscles. ...
Article
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This study examined the combined effect of exercise induced hyperthermia and dehydration on neuromuscular function in human subjects. Six trained male runners ran for 40 min on a treadmill at 65% of their maximal aerobic velocity while wearing a tracksuit covered with an impermeable jacket and pants to impair the evaporation of sweat. These stressful experimental running conditions led the runners to a physiological status close to exhaustion. On average, the 40 min run ended at a heart rate of 196 (SD 8) beats · min−1, a tympanic temperature of 40 (SD 0.3) °C and with a loss of body mass of 2 (SD 0.5)%. Pre- and post-running strength tests included measurements of maximal knee extension and flexion torques in both isometric and isokinetic (at 60 and 240° · s−1) conditions. A 20 s endurance test at 240° · s−1 was also performed. Surface electromyographic (EMG) activity was recorded from six knee extensor and flexor muscles during the entire protocol. The treadmill run led to clear decrements in maximal extension torque and EMG activity both in isometric and at the slowest isokinetic velocity (60° · s−1). However, no differences in these parameters were observed at 240° · s−1. Furthermore, the EMG patterns of the major knee extensor and flexor muscles remained remarkably stable during the treadmill run. These results demonstrate that the exercise-induced hyperthermia and dehydration in the present experiments had only minor effects on the neuromuscular performance. However, it is also suggested that high internal body temperature per se could limit the production of high force levels.
... These investigations were ordered to present a continuum from the lowest to most severe water deficit. Caution should be employed when comparing the results of these different investigations (within Table 3 hypohydration was achieved by fluid restriction in three (12,13,61) and by a combination of exercise and heat exposure in the fourth (144). Therefore, prolonged fluid restriction, perhaps accompanied by a caloric deficit (13,61) was the dehydration method which most often reduced muscular strength. ...
... ).12. WEBSTER It. ...
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During exercise in the heat, sweat output often exceeds water intake resulting in hypohydration, which defined as body fluid deficit. This fluid deficit is comprised of water loss from both the intracellular and extracellular fluid compartments. There is no evidence that hypohydration can benefit exercise performance; in addition, man cannot adapt to chronic dehydration. Exercise tasks that primarily require aerobic metabolism and that are prolonged will more likely be adversely influenced by hypohydration than exercise tasks that require anaerobic metabolism as well as muscular strength and power. Likewise, the warmer the environmental temperature, the greater the potential for hypohydration to cause decrements in all types of exercise performance. Hypohydration causes a greater heat storage and reduces endurance as well as maximal effort exercise performance in comparison to euhydration levels. The greater heat storage is mediated by a decreased sweating rate (evaporative heat loss) as well as by a decreased cutaneous blood flow (dry heat loss). These response decrements have been attributed to both a plasma hyperosmolality and a reduced blood volume. The reduced blood volume also makes it difficult to maintain an adequate cardiac output during exercise-heat stress. Finally, preliminary data indicate that hypohydration does not alter muscle glycogen utilization during exercise or the glycogen resynthesis during recovery from exercise. Keywords: Dehydration; Hypohydration; Exercise performance; Body water requirements; Temperature regulation.
... In fact, the increase in plasma creatinine clearance and decreased GFR are closely related to stage of dehydration (Whiting et al. 1984). Besides these parameters, the reduction in weight gain, low water intake, and decreased urine volume detected in a previous study (da Silva et al. 2013) are related and measure the condition of dehydration (Bosco et al. 1974). ...
Article
Soil ingestion can be an important route of exposure to contaminants present in the environment. This study examined the effects of exposure to contaminants in aqueous soil extracts from an industrial urban settlement in renal biochemical parameters of treated rats. Male Wistar rats were gavaged with an aqueous soil extract, from the municipality of Rio Grande, Southern Brazil. After exposure, plasma and urine concentrations and plasma protein were assessed compared to rats treated with aqueous soil from relatively unpolluted site (control soil). There was increase in plasma creatinine and total protein in urine, and a decreased glomerular filtration rate in treated rats compared to control. It is possible that Cd, Cr, As, Cu, Pb, Zn, and Ni analyzed in the soil samples and unidentified components may have provoked the observed changes in renal biochemistry of the exposed rat. This may suggest that exposure to contaminated soils can cause damage to the viscera in mammals and it is of public health importance.
... Whilst there is a substantial body of literature that documents the effects of hypohydration (reduced total body water) on endurance exercise performance (Sawka et al. 2007), less focus has been diverted to the effects of fluid loss on muscle performance. Some studies have investigated the effects of hypohydration on outcome measures, such as power (Viitasalo et al. 1987; Judelson et al. 2007b; Hayes and Morse 2010), muscular endurance (Bosco et al. 1974; Montain et al. 1998; Greiwe et al. 1998; Bigard et al. 2001; Ftaiti et al. 2001; Montain and Tharion 2010), and strength (Bosco et al. 1974; Greiwe et al. 1998; Montain et al. 1998; Ftaiti et al. 2001; Hayes and Morse 2010), but with equivocal results. These indices of neuromuscular performance are important for athletic endeavours; however, other markers of neuromuscular performance capability, such as electromechanical delay, which is also important in explosive athletic performance but integral in the maintenance of joint stabilisation and injury avoidance, have not been examined. ...
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This study investigated the effects of hypohydration by fluid restriction on voluntary and evoked indices of neuromuscular performance at a functional joint angle. Measures of static volitional peak force (2-3-s maximal muscle actions) and evoked peak twitch force, electromechanical delay, and rate of force development were obtained from the knee extensors (30° knee flexion) of 10 males (age, 24 (4) years; height, 1.76 (0.10) m; body mass, 78.7 (9.13) kg (mean (SD))) prior to and immediately following 24 h of (i) euhydration (EU) and (ii) hypohydration (HYP). Neuromuscular performance was also assessed in response to a fatiguing task (3 × 30-s maximal static knee extensions) following each condition. Repeated-measures ANOVAs showed that HYP was associated with a significant 2.1% loss in body mass (p < 0.001) and a 7.8% reduction in volitional peak force (p < 0.05). Following fatigue, data indicated statistically similar levels of impairment to volitional peak force (11.6%, p < 0.01) and rate of force development (21.0%, p < 0.01) between conditions (EU; HYP). No changes to any other indices of performance were observed. The substantive hypohydration-induced deficits to muscle strength at this functional joint angle might convey a decreased performance capability and should be considered by the hypohydrated athlete. Whilst hypohydration did not affect fatigue-related performance of the knee extensors, the additive changes associated with lower baseline levels of strength performance (7.8%) and fatigue (11.6%) coupled with slower rate of muscle force production (from 0-100 ms) following fatigue may present significant challenges to the maintenance of dynamic knee joint stability, particularly at this vulnerable joint position.
... These results describing SVJ performance do not necessarily reXect the physiological capacity of muscle, because the decreased M b characteristic of hypohydration might oVset the reduced muscular strength observed in this investigation and previous publications (Cheuvront et al. 2006; Gutierrez et al. 2003). Hypohydration signiWcantly decreased peak torque after three or more exposures (2.6 § 0.8% M b loss or more) in isokinetic conditions at 30° s ¡1 and after one exposure (1.0 § 0.5% M b loss or more) in isometric conditions (Table 1), supporting some (Bosco et al. 1974), but not all (Bigard et al. 2001; Viitasalo et al. 1987 ) previous investigations into the eVect of hydration on single, maximal eVort force production. This decrement in peak torque was not observed in the isokinetric contractions at 120° s ¡1 . ...
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This study examined the effect of exercise- and heat-induced dehydration on strength, jump capacity and neuromuscular function. Twelve recreationally active males completed six resistance exercise bouts (baseline and after each 5 exposure sessions) in an increasing state of hypohydration obtained by repeated heat exposure and exercise sessions (5 periods of 20 min jogging at up to approximately 80% age predicted heart rate maximum at 48.5 +/- 0.48 degrees C, relative humidity 50 +/- 4%). Relative to starting values, body mass decreased 1.0 +/- 0.5, 1.9 +/- 0.7, 2.6 +/- 0.8, 3.3 +/- 0.9 and 3.9 +/- 1.0% after exposure 1, 2, 3, 4 and 5, respectively. However, plasma volume remained constant. No significant differences existed amongst trials in vertical jump height, electromyography data or isokinetic leg extension at a rate of 120 degrees s(-1). Isometric leg extensions were significantly reduced (P < 0.05) after the first (1% body mass loss) and subsequent exposures in comparison to baseline. Isokinetic leg extensions at a rate of 30 degrees s(-1) were significantly reduced after the third (2.6% body mass loss) and subsequent exposures compared with baseline. No dose response was identified in any of the tested variables yet a threshold was observed in isometric and isokinetic strength at 30 degrees s(-1). In conclusion, dehydration caused by jogging in the heat had no effect on vertical jumping or isokinetic leg extensions at a rate of 120 degrees s(-1). Alternatively, exercise-induced dehydration was detrimental to isometric and isokinetic leg extensions at a rate of 30 degrees s(-1), suggesting the force-velocity relationship in hypohydration merits further research.
... Factors which, in isolation, are likely to challenge body water balance and when combined, increase the likelihood of dehydration. In nonfirefighting contexts, fluid restricted and hypohydrated individuals have displayed increased cardiovascular strain (Sharkey, 1999), reduced physical work capacity (Adolph, 1947;Bosco et al., 1974;Coyle, 2004;Craig and Cummings, 1966;Houston et al., 1981;Webster et al., 1990), and elevated core temperatures (Sharkey, 1999), which can eventually lead to exhaustion or collapse (Adolph, 1947;Greenleaf and Castle, 1971;Pitts et al., 1944;Sawka et al., 1985). To reduce the likelihood of dehydration and perceived health and safety risks, fire agencies in Australia and elsewhere, prescribe target drinking rates for their firefighters to follow whilst suppressing wildfire (CFS, 2008). ...
Article
Unlabelled: The purpose of this study was to examine 1) wildfire fighters' ability to consume the prescribed fluid volume (1200 mL h(-1)), 2) the effect of fluid intake on plasma sodium and hydration, and 3) the effect of fluid intake on firefighters' heart rate, core temperature and activity during emergency suppression shifts. Methods: Thirty-four firefighters were divided into ad libitum (AD, n = 17) and prescribed (PR, n = 17) drinking groups. Results: PR drinkers did not meet the prescribed fluid target, yet consumed over double the volume of AD drinkers. No differences between groups in plasma sodium or hydration were noted. PR drinking resulted in lower core temperature between 2 and 6 h. This did not coincide with reduced cardiovascular strain, greater work activity or larger distances covered when compared to AD drinkers. Conclusion: Extra fluid consumption (above AD) did not improve firefighter activity or physiological function (though PR firefighters core temperature was lower earlier in their shift). Firefighter can self-regulate their fluid consumption behavior and work rate to leave the fireground euhydrated.
... As an emerging strength training method, vibration training garners increasing attention from experts at home and abroad for it can effectively enhance muscular strength and explosive force with relatively small load. According to a range of researches, Bosco et al. [1] found that vibration training cannot only help improve the muscle's maximum strength but also has positive effects on the muscle's rapid strength and strength endurance. Then some scholars held that [2,3] vibration stimulation can change hormone level in men's blood and thus exert positive influence on improvement of the subjects' balance ability, leaping ability, and proprioception. ...
... Robust fluid loss (5-10% of body weight) can be well tolerated by healthy individuals at rest [3], yet a 2-3% fluid loss impairs exercise performance [3][4][5][6][7][8][9][10][11]. In a study by Armstrong et al. [4], competitive runners were tested in time trials of varying distances as well as time to exhaustion under conditions of hydration and dehydration in a crossover design. ...
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Background In cases of dehydration exceeding a 2% loss of body weight, athletic performance can be significantly compromised. Carbohydrate and/or electrolyte containing beverages have been effective for rehydration and recovery of performance, yet amino acid containing beverages remain unexamined. Therefore, the purpose of this study is to compare the rehydration capabilities of an electrolyte-carbohydrate (EC), electrolyte-branched chain amino acid (EA), and flavored water (FW) beverages. Methods Twenty men (n = 10; 26.7 ± 4.8 years; 174.3 ± 6.4 cm; 74.2 ± 10.9 kg) and women (n = 10; 27.1 ± 4.7 years; 175.3 ± 7.9 cm; 71.0 ± 6.5 kg) participated in this crossover study. For each trial, subjects were dehydrated, provided one of three random beverages, and monitored for the following three hours. Measurements were collected prior to and immediately after dehydration and 4 hours after dehydration (3 hours after rehydration) (AE = −2.5 ± 0.55%; CE = −2.2 ± 0.43%; FW = −2.5 ± 0.62%). Measurements collected at each time point were urine volume, urine specific gravity, drink volume, and fluid retention. Results No significant differences (p > 0.05) existed between beverages for urine volume, drink volume, or fluid retention for any time-point. Treatment x time interactions existed for urine specific gravity (USG) (p < 0.05). Post hoc analysis revealed differences occurred between the FW and EA beverages (p = 0.003) and between the EC and EA beverages (p = 0.007) at 4 hours after rehydration. Wherein, EA USG returned to baseline at 4 hours post-dehydration (mean difference from pre to 4 hours post-dehydration = -0.0002; p > 0.05) while both EC (-0.0067) and FW (-0.0051) continued to produce dilute urine and failed to return to baseline at the same time-point (p < 0.05). Conclusion Because no differences existed for fluid retention, urine or drink volume at any time point, yet USG returned to baseline during the EA trial, an EA supplement may enhance cellular rehydration rate compared to an EC or FW beverage in healthy men and women after acute dehydration of around 2% body mass loss.
... Therefore, caution should be used when interpreting this as a true measure of anaerobic performance. Torranin et al. (1979) likewise reported a significant decrease in muscular endurance measured by the ability to maintain 75% of maximal voluntary contraction (~ 40 s) after dehydration by 4% via sauna, while Bosco et al. (1974) reported a 9% decrease in muscular endurance (2 min timed sit-up test) after a 5.7% reduction in body mass. Again, increased exercise duration, which magnifies reliance on aerobic (vs. ...
Article
This study examined the effects of dehydration on intermittent sprint performance and perceptual responses. Eight male collegiate baseball players completed intermittent sprints either dehydrated (DEHY) by 3% body mass or euhydrated (EU). Body mass was reduced via exercise in the heat with controlled fluid restriction occurring 1day prior to the trial. Participants completed 24, 30m sprints, divided into 3 bouts of 8 sprints with 45sec rest between each sprint and 3min between each bout. Perceived recovery status (PRS) scale was recorded prior to the start of each trial. Heart rate (HR), RPE (0-10 OMNI scale), and perceived readiness (PR) scale was recorded after every sprint and session RPE (SRPE) was recorded 20min after completing the entire session. A 2 (condition) x 3 (bout of sprints) repeated measures ANOVA revealed a significant main effect of condition on mean sprint time (p = 0.03), HR (p < 0.01), RPE (p = 0.01), and PR (p = 0.02). Post-hoc tests showed significantly faster mean sprint times for EU vs DEHY during the second (4.87 ± 0.29 vs 5.03 ± 0.33s; p = 0.01) and third bout of sprints (4.91 ± 0.29 vs 5.12 ± 0.44s; p = 0.02). HR was also significantly lower (p < 0.05) for EU during the second bout and third bout. Post-hoc measures also showed significantly impaired (p < 0.05) feelings of recovery (PRS) prior to exercise and increased (p < 0.05) perceptual strain before each bout (PR) during the second and third bouts of repeated sprint work (i.e., RPE and PR) and following the total session (SRPE) in the DEHY condition. Dehydration impaired sprint performance, negatively altered perception of recovery status prior to exercise, and increased RPE and HR response.
... One element identified with the potential to impair firefighter health, safety and performance is hypohydration (Hendrie et al., 1997). In non-firefighting contexts, hypohydrated individuals display increases in cardiovascular strain (Sharkey, 1999), reductions in physical work capacity (Adolph, 1947;Bosco et al., 1974;Coyle, 2004;Craig and Cummings, 1966;Houston et al., 1981;Webster et al., 1990), and elevations in core temperature (Sharkey, 1999), which can eventually lead to exhaustion or collapse (Adolph, 1947;Greenleaf and Castle, 1971;Pitts et al., 1944;Sawka et al., 1985). Unfortunately there has been limited scientific exploration (Cuddy et al., 2008;Hendrie et al., 1997;Ruby et al., 2003) into hypohydration and its proposed ill-effects on wildfire fighters. ...
Article
Wildfire fighters are known to report to work in a hypohydrated state, which may compromise their work performance and health. To evaluate whether ingesting a bolus of fluid before the shift had any effect on firefighters' fluid consumption, core temperature, or the time they spent in high heart rate and work activity zones when fighting emergency wildfires. Thirty-two firefighters were divided into non-bolus (AD) and pre-shift drinking bolus (PS, 500 ml water) groups. Firefighters began work hypohydrated as indicated by urine colour, specific gravity and plasma osmolality (P(osm)) results. Post-shift, firefighters were classified as euhydrated according to P(osm) and hypohydrated by urinary markers. No significant differences existed between the drinking groups in pre- or post-shift hydration status, total fluid intake, activity, heart rate or core temperature. Consuming a bolus of fluid, pre-shift provided no benefit over non-consumption as both groups had consumed equivalent ad libitum volumes of fluid, 2.5 h into the shift. No benefits of bolus consumption were observed in firefighter activity, heart rate response or core temperature response across the shift in the mild weather conditions experienced. Ad libitum drinking was adequate to facilitate rehydration in firefighters upon completion of their emergency firefighting work shift.
Article
Although many studies have attempted to examine the effect of hypohydration on strength, power, and high-intensity endurance, few have successfully isolated changes in total body water from other variables that alter performance (e.g., increased core temperature), and none have documented the influence of hypohydration on an isotonic, multiset, multirepetition exercise bout typical of resistance exercise training. Further, no investigations document the effect of hypohydration on the ability of the central nervous system to stimulate the musculature, despite numerous scientists suggesting this possibility. The purposes of this study were to examine the isolated effect of hydration state on 1) strength, power, and the performance of acute resistance exercise, and 2) central activation ratio (CAR). Seven healthy resistance-trained males (age = 23 +/- 4 yr, body mass = 87.8 +/- 6.8 kg, body fat = 11.5 +/- 5.2%) completed three resistance exercise bouts in different hydration states: euhydrated (EU), hypohydrated by approximately 2.5% body mass (HY25), and hypohydrated by approximately 5.0% body mass (HY50). Investigators manipulated hydration status via exercise-heat stress and controlled fluid intake 1 d preceding testing. Body mass decreased 2.4 +/- 0.4 and 4.8 +/- 0.4% during HY25 and HY50, respectively. No significant differences existed among trials in vertical jump height, peak lower-body power (assessed via jump squat), or peak lower-body force (assessed via isometric back squat). CAR tended to decrease as hypohydration increased (EU = 95.6 +/- 4.9%, HY25 = 94.0 +/- 3.1%, HY50 = 92.5 +/- 5.1%; P = 0.075, eta(p)(2) = 0.41). When evaluated as a function of the percentage of total work completed during a six-set back squat protocol, hypohydration significantly decreased resistance exercise performance during sets 2-3 and 2-5 for HY25 and HY50, respectively. These data indicate that hypohydration attenuates resistance exercise performance; the role of central drive as the causative mechanism driving these responses merits further research.
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Significant scientific evidence documents the deleterious effects of hypohydration (reduced total body water) on endurance exercise performance; however, the influence of hypohydration on muscular strength, power and high-intensity endurance (maximal activities lasting >30 seconds but <2 minutes) is poorly understood due to the inconsistent results produced by previous investigations. Several subtle methodological choices that exacerbate or attenuate the apparent effects of hypohydration explain much of this variability. After accounting for these factors, hypohydration appears to consistently attenuate strength (by approximately 2%), power (by approximately 3%) and high-intensity endurance (by approximately 10%), suggesting alterations in total body water affect some aspect of force generation. Unfortunately, the relationships between performance decrement and crucial variables such as mode, degree and rate of water loss remain unclear due to a lack of suitably uninfluenced data. The physiological demands of strength, power and high-intensity endurance couple with a lack of scientific support to argue against previous hypotheses that suggest alterations in cardiovascular, metabolic and/or buffering function represent the performance-reducing mechanism of hypohydration. On the other hand, hypohydration might directly affect some component of the neuromuscular system, but this possibility awaits thorough evaluation. A critical review of the available literature suggests hypohydration limits strength, power and high-intensity endurance and, therefore, is an important factor to consider when attempting to maximise muscular performance in athletic, military and industrial settings.
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To present the critical issue of exercise in the heat in a format that provides physiologic foundations (Part I) and then applies the established literature to substantial, usable guidelines that athletic trainers can implement on a daily basis when working with athletes who exercise in the heat (Part II). The databases MEDLINE and SPORT Discus were searched from 1980 to 1999, with the terms "hydration," "heat," "dehydration," "cardiovascular," "thermoregulatory," "physiology," and "exercise," among others. The remaining citations are knowledge base. Part I introduces athletic trainers to some of the basic physiologic and performance responses to exercise in the heat. The medical supervision of athletes who exercise in hot environments requires an in-depth understanding of basic physiologic responses and performance considerations. Part I of this article aims to lay the scientific foundation for efficient implementation of the guidelines for monitoring athletic performance in the heat provided in Part II.
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To present recommendations to optimize the fluid-replacement practices of athletes. Dehydration can compromise athletic performance and increase the risk of exertional heat injury. Athletes do not voluntarily drink sufficient water to prevent dehydration during physical activity. Drinking behavior can be modified by education, increasing accessibility, and optimizing palatability. However, excessive overdrinking should be avoided because it can also compromise physical performance and health. We provide practical recommendations regarding fluid replacement for athletes. Educate athletes regarding the risks of dehydration and overhydration on health and physical performance. Work with individual athletes to develop fluid-replacement practices that optimize hydration status before, during, and after competition.
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To determine weight (water) loss levels for onset of muscular strength and endurance changes during deconditioning. Seven men (27-40 yr) performed maximal shoulder-, knee-, and ankle-joint isometric (0 degree.s(-1) load) and isokinetic (60 degrees, 120 degrees, 180 degrees.s(-1) velocity) exercise tests during ambulatory control (AC), after 6 h of 6 degrees head-down tilt (HDT; dry-bulb temp. = 23.2 +/- SD 0.6 degrees C, relative humidity = 31.1+/- 11.1%) and after 6 h of 80 degrees foot-down head-out water immersion (WI; water temp. = 35.0 +/- SD 0.1 degree C) treatments. Weight (water) loss after HDT (1.10 +/- SE 0.14 kg, 1.4 +/- 0.2% body wt) and WI (1.54+/- 0.19 kg, 2.0 +/- 0.2% body wt) were not different, but urinary excretion with WI (1,354 +/- 142 ml.6 h(-1)) was 28% greater (p < 0.05) than that of 975 +/- 139 ml.6 h(-1) with HDT. Muscular endurance (total work; maximal flexion-extension of the non-dominant knee at 180 degrees.s(-1) for 30 s) was not different between AC and the WI or HDT treatments. Shoulder-, knee-, and ankle-joint strength was unchanged except for three knee-joint peak torques: AC torque (120 degrees.s(-1), 285 +/- 20 Nm) decreased to 268 +/- 21 Nm (delta = -6%, p < 0.05) with WI; and AC torques (180 degrees.s(-1), 260 +/- 19 Nm) decreased to 236 +/- 15 Nm (delta = -9%, p < 0.01) with HDT, and to 235 +/- 19 Nm (delta = -10%, p < 0.01) with WI. Thus, the total body hypohydration threshold level for shoulder- and ankle-joint strength and endurance decrements is more than 2% body weight (water) loss, while significant reduction in knee-joint muscular strength-endurance occurred only at moderate (120 degrees.s(-1) and lighter (180 degrees.s(-1)) loads with body weight loss of 1.4-2.0% following WI or HDT, respectively. These weight (water) losses and knee-joint strength decrements are somewhat less than the mean weight loss of 2.6% and knee-joint strength decrements of 6-20% of American astronauts after Skylab flights to 84 d.
Eight young men were tested for strength, anaerobic capacity and aerobic endurance in a post absorptive state and after a 3.5 day fast. Strength was tested both isokinetically (elbow flexors, 0.52 rad·s−1 and 3.14 rad·s−1) and isometrically. Anaerobic capacity was evaluated by having subjects perform 50 rapidly repeated isokinetic contractions of the elbow flexors at 3.14 rad·s−1. Aerobic endurance was measured as time to volitional fatigue during a cycle ergometer exercise at 45% \(V_{O_{2{\text{max}}} }\). Measures of \(V_{{\text{O}}_{\text{2}} }\), V E, heart rate, and ratings of perceived exertion were obtained prior to and during the cycle exercise. The 3.5 day fast did not influence isometric strength, anaerobic capacity or aerobic endurance. Isokinetic strength was significantly reduced (∼ 10%) at both velocities. \(V_{{\text{O}}_{\text{2}} }\), V E and perceived exertion were not affected by fasting. Fasting significantly increased heart rate during exercise but not at rest. It was concluded that there are minimal impairments in physical performance parameters measured here as a result of a 3.5 day fast.
Chapter
Nutritionists have focused their special attention on work performance and fitness for many reasons during the last two decades. We can mention here some efforts to insure desirable growth and development not only from the point of view of body size but also from the point of view of the functional capacity, care for health, and its prognosis in later periods of life, as well as an active life. Further, there exists also the problem of economic productivity, an important concern both for the individual and for the national economy.
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This study reports measurements of hydration status among firefighters prior to training, documents changes in hydration status after prolonged firefighting training, and reports the utility of salivary measurements to assess changes in hydration in field environments. Nude body mass measurements as well as urinary and salivary measurements of hydration status were taken before and after approximately three hours of firefighting training activities. Initial hydration status was assessed via urinary and salivary measures. Changes in body mass and total body water were measured following firefighting activity and correlated with changes in urinary and salivary measures of hydration. The most important findings of this study were that a high percentage of firefighters arrived at training in a significantly or seriously dehydrated state; that firefighters lost a significant amount of body mass because of firefighting operations; and that portable salivary osmolality measurements showed much stronger correlation with changes in hydration status after firefighting operations than standard urinary measurements did. Firefighters arriving in a dehydrated state are at risk for heat injuries and may be in a physically and/or psychologically compromised state at the outset of firefighter training. Even during cool autumn days with ample fluids available, firefighters experience dehydration during typical firefighting activities, so the ability to measure hydration status throughout such activities may be important. Our data suggest that quantification of changes in hydration status through salivary osmolality measurements may provide a viable field measurement tool for such activities.
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The purpose of this study was to test the effect of acute thermal hypohydration on the muscle endurance performance of three groups of differentially trained subjects. Group I consisted of six anaerobically trained athletes, Group II consisted of five aerobically trained athletes, and Group III consisted of six sedentary individuals. Experimental trials involved maximal leg extensions performed on a Cybex II dynamometer under conditions of euhydration and hypohydration of minus 3% body weight. Integrated electromyographic data were also collected during each trial to factor out motivation as a variable. The maximum number of leg extension repetitions performed at or above 50% of each subject's peak torque output were compared between treatments and among the three groups. A 2 x 3 factorial analysis of variance (ANOVA) showed a significant decrease in muscle endurance when comparing euhydration to hypohydration among the anaerobically trained subjects as well as among the sedentary subjects (P less than 0.05). The aerobically trained subjects showed no significant decline in muscle endurance when comparing performance under both experimental conditions. It was hypothesized that the training adaptations that occur with aerobic conditioning and are primarily associated with increased plasma volume may be the key to explaining these results.
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This study examined firstly, the effects of 24 hours of dehydration on body weight, plasma volume and various urinary variables and compared the efficacy of drinking water and solutions of varying sodium chloride concentration in restoring plasma volume after dehydration; and secondly, the metabolic processes during performance in a maximal rowing trial following partial rehydration with water after rapid weight loss.
Article
To examine the effects of rapid dehydration on isometric muscular strength and endurance, seven men were tested at baseline (control) and after a dehydration (dHST) and a euhydration (eHST) heat stress trial. The dHST consisted of intermittent sauna exposure until 4% of body mass was lost, whereas the eHST consisted of intermittent sauna exposure (same duration as dHST) with water replacement. Peak torque was determined for the knee extensors and elbow flexors during three isometric maximal voluntary contractions. Time to fatigue was determined by holding a maximal voluntary contraction until torque dropped below 50% peak torque for 5 s. Strength and endurance were assessed 3.5 h after the HSTs (no food or water intake). Body mass was decreased 3.8+/-0.4% post dHST and 0.4+/-0.3% post eHST. Plasma volume was decreased 7.5+/-4.6% and 5.7+/-4.4%, 60 and 120 min post dHST, respectively. A small (1.6 mEq x L[-1]) but significant increase was found for serum Na+ concentration 60 min post dHST but had returned to predehydration level 120 min post dHST. Serum K+ and myoglobin concentrations were not affected by HSTs. Peak torque was not different (P > 0.05) among control, dHST, and eHST for the knee extensors (Mean (Nm)+/-SD, 285+/-79, 311+/-113, and 297+/-79) and elbow flexors (79+/-12, 83+/-15, and 80+/-12). Time to fatigue was not different (P > 0.05) among control, dHST and eHST for the knee extensors (Mean (s)+/-SD. 42.4+/-11.5, 45.3+/-7.6, and 41.8+/-6.0) and elbow flexors (48.2+/-8.9, 44.0+/-9.4, and 46.0+/-6.4). These results provide evidence that isometric strength and endurance are unaffected 3.5 h after dehydration of approximately 4% body mass.
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Excessive weight loss just prior to competition can result in reduced performance. Weight reduction, if necessary, should occur pre-season and weight should be maintained throughout the season. This will allow the wrestler to train and compete at his very best. Glycogen loading should be used no more than two or three times a year (if at all) by wrestlers. The coach and athlete should be aware of the undesirable side effects… water retention (with resulting weight gain) and stiffness.
Article
Significant scientific evidence documents the deleterious effects of hypohydration (reduced total body water) on endurance exercise performance; however, the influence of hypohydration on muscular strength, power and high-intensity endurance (maximal activities lasting >30 seconds but <2 minutes) is poorly understood due to the inconsistent results produced by previous investigations. Several subtle methodological choices that exacerbate or attenuate the apparent effects of hypohydration explain much of this variability. After accounting for these factors, hypohydration appears to consistently attenuate strength (by ≈2%), power (by ≈3%) and high-intensity endurance (by ∼10%), suggesting alterations in total body water affect some aspect of force generation. Unfortunately, the relationships between performance decrement and crucial variables such as mode, degree and rate of water loss remain unclear due to a lack of suitably uninfluenced data. The physiological demands of strength, power and high-intensity endurance couple with a lack of scientific support to argue against previous hypotheses that suggest alterations in cardiovascular, metabolic and/or buffering function represent the performance-reducing mechanism of hypohydration. On the other hand, hypohydration might directly affect some component of the neuromuscular system, but this possibility awaits thorough evaluation. A critical review of the available literature suggests hypohydration limits strength, power and highintensity endurance and, therefore, is an important factor to consider when attempting to maximise muscular performance in athletic, military and industrial settings.
Article
Weight categorized athletes use a variety of techniques to induce rapid weight loss (RWL) in the days leading up to weigh in. This study examined the fluid and electrolyte balance responses to 24-hr fluid restriction (FR), energy restriction (ER) and fluid and energy restriction (F+ER) compared with a control trial (C), which are commonly used techniques to induce RWL in weight category sports. Twelve subjects (six male, six female) received adequate energy and water (C) intake, adequate energy and restricted water (~10% of C; FR) intake, restricted energy (~25% of C) and adequate water (ER) intake or restricted energy (~25% of C) and restricted (~10% of C) water intake (F+ER) in a randomized counterbalanced order. Subjects visited the laboratory at 0 hr, 12 hr, and 24 hr for blood and urine sample collection. Total body mass loss was 0.33% (C), 1.88% (FR), 1.97% (ER), and 2.44% (F+ER). Plasma volume was reduced at 24 hr during FR, ER, and F+ER, while serum osmolality was increased at 24 hr for FR and F+ER and was greater at 24 hr for FR compared with all other trials. Negative balances of sodium, potassium, and chloride developed during ER and F+ER but not during C and FR. These results demonstrate that 24 hr fluid and/ or energy restriction significantly reduces body mass and plasma volume, but has a disparate effect on serum osmolality, resulting in hypertonic hypohydration during FR and isotonic hypohydration during ER. These findings might be explained by the difference in electrolyte balance between the trials.
Article
Eleven university wrestlers were tested on three occasions in a 6-min fatigue bout during which the subject squeezed a hand dynamometer maximally and then relaxed every other second until a total of 180 contractions had been completed. Testing was administered (1) following a 5% body weight loss within a 3-day period just prior to testing, (2) after a 5% body weight loss followed by an attempt to rehydrate to the original weight, and (3) under a control condition with no weight loss. All subjects were tested under all conditions with the order of testing assigned at random. One-way ANOVA failed to reveal any effects of the rapid weight loss or attempted rehydration on initial strength, final strength, or the force-time integrals. In addition, a 3 × 13 ANOVA for hydration level across the 13 observation times failed to reveal any interaction between the two factors. A mathematical analysis of the force-time values revealed that fatigue progressed in an exponential pattern described by a curve with two major components.
Chapter
The need to maximize hydration and nutrition is valuable in athletes at all levels, from the weekend warrior to the elite professional athlete. Sports nutrition-associated issues, such as fatigue, loss of strength and stamina, and loss of speed, can negatively affect athletic performance. There is significant science dedicated to the optimal distribution of nutrients and fluids, based on exercise of various intensities and durations. This includes pre-exercise, during exercise, and post-exercise/recovery energy requirements. It is imperative the sports medicine physician, team physician, coach, and athlete understand the distribution of the energy substrates and proper fluid intake. Adequate food and fluid consumed by the athlete will maximize exercise performance and improve recovery time. Knowledge and education for the athlete regarding proper hydration and nutrition will also protect an athlete from serious detrimental effects, including dehydration, heat stroke, hyponatremia, and even death. This chapter reviews the principles for nutritional management for athletes.
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