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Impact of dehydration on a full body resistance exercise protocol

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Abstract

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.

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... Interestingly, in cases where individuals were hypohydrated and heart rate during exercise was controlled, heart rate was significantly elevated after exercise compared with a hydrated control, resulting in a slower recovery rate (8). Similarly, a study examining the effects of dehydration on resistance exercise found that 3% body mass losses resulted in higher preset heart rates and also hindered heart rate recovery (20). ...
... Although research on the impact of hydration on anaerobic activity is not as prevalent, some studies have found decrements in anaerobic performance with fluid deficits ranging from 1 to more than 3% of body mass losses (3,4,11,16,19,20,27). In some studies, fluid deficit resulted in decrements in skill performance during basketball and soccer activities (4,27). ...
... In some studies, fluid deficit resulted in decrements in skill performance during basketball and soccer activities (4,27). Strength and power have also been negatively affected by dehydration (16,19,20). Hayes and Morse (16) found that dehydration had no effect on vertical jumping or isokinetic leg extensions at 120˚per second; however, dehydration impaired isometric and isokinetic leg extensions at 30˚per second. ...
Article
WHEN DEVELOPING FLUID REPLACEMENT GUIDELINES FOR EXERCISING INDIVIDUALS, A VARIETY OF FACTORS SHOULD BE TAKEN INTO CONSIDERATION. THE ENVIRONMENTAL CONDITIONS, INTENSITY LEVEL, DURATION OF EXERCISE, VARIABILITY IN SWEAT RATE, AND LEVEL OF HEAT ACCLIMATIZATION ARE AMONG THOSE FACTORS. DETERMINING INDIVIDUAL SWEAT RATES AND ASSESSING HYDRATION STATUS SHOULD HELP GUIDE SPECIFIC RECOMMENDATIONS. THE TYPE OF EXERCISE TOGETHER WITH THE SPECIFIC NEEDS OF THE INDIVIDUAL WILL HELP DETERMINE THE FLUID REPLACEMENT BEVERAGE THAT WOULD BE MOST BENEFICIAL. EDUCATING INDIVIDUALS ABOUT THEIR OWN FLUID NEEDS WILL ENSURE THAT THEY EXERCISE SAFELY AND PERFORM WELL.
... In 57 out of the 61 trials reviewed, dehydration was accomplished via passive heat exposure (n = 11) [42,47,[50][51][52][53][54][55][56] or physical activity (n = 47), conducted in a thermoneutral laboratory ≤25°C (n = 16) [24,25,29,35,48,55,[57][58][59][60][61], heated environmental chamber (n = 28) [22,29,33,36,37,41,46,49,[62][63][64][65][66][67][68][69][70][71] or environmental conditions not specified (n = 3) [72,73]. The remaining trials reduced body water content through warm water immersion (n = 2) [74,75] or dietary fluid restriction in combination with 2-h moderate intensity exercise 24 h prior to testing performance (n = 2) [76,77]. In 46 trials (74%) [22, 24, 29, 36, 37, 41, 42, 46, 47, 49-53, 55-59, 61-63, 66, 67, 71, 73-77], dehydration yielded BM losses ≥2%. ...
... In 46 trials (74%) [22, 24, 29, 36, 37, 41, 42, 46, 47, 49-53, 55-59, 61-63, 66, 67, 71, 73-77], dehydration yielded BM losses ≥2%. Of these, 27 trials (43%) dehydrated participants by ≥3.0% of initial BM [22,24,29,37,41,42,46,50,52,53,56,61,62,66,67,[74][75][76][77]. Mean BM losses ranged from 1.3 [72] to 4.2% [41]. ...
... Across the 8 trials reviewed, 22 separate performance tests were identified. The majority were knee extension or elbow flexion exercise tasks, at variable intensities (n = 18 tasks) [46,49,52,53,57,66], although 2 trials measured performance via repetition lifts [54,74]. Individuals who were accustomed to performing resistance exercise were rarely studied [54,74]. ...
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Background The deleterious effects of dehydration on athletic and cognitive performance have been well documented. As such, dehydrated individuals are advised to consume fluid in volumes equivalent to 1.25 to 1.5 L kg−1 body mass (BM) lost to restore body water content. However, individuals undertaking subsequent activity may have limited time to consume fluid. Within this context, the impact of fluid intake practices is unclear. This systematic review investigated the effect of fluid consumption following a period of dehydration on subsequent athletic and cognitive performance. Methods PubMed (MEDLINE), Web of Science (via Thomas Reuters) and Scopus databases were searched for articles reporting on athletic (categorized as: continuous, intermittent, resistance, sport-specific and balance exercise) or cognitive performance following dehydration of participants under control (no fluid) and intervention (fluid intake) conditions. Meta-analytic procedures determined intervention efficacy for continuous exercise performance. ResultsSixty-four trials (n = 643 participants) derived from 42 publications were reviewed. Dehydration decreased BM by 1.3–4.2%, and fluid intake was equivalent to 0.4–1.55 L kg−1 BM lost. Fluid intake significantly improved continuous exercise performance (22 trials), Hedges’ g = 0.46, 95% CI 0.32, 0.61. Improvement was greatest when exercise was performed in hotter environments and over longer durations. The volume or timing of fluid consumption did not influence the magnitude of this effect. Evidence indicating a benefit of fluid intake on intermittent (10 trials), resistance (9 trials), sport-specific (6 trials) and balance (2 trials) exercise and on cognitive performance (15 trials) was less apparent and requires further elucidation. Conclusions Fluid consumption following dehydration may improve continuous exercise performance under heat stress conditions, even when the body water deficit is modest and fluid intake is inadequate for complete rehydration.
... Studies have reported anaerobic performance decrements associated with hypohydration (6,14,16,17,21,22,30,45), whereas others show no influence (6,7,14,17,18,44,45). A possible explanation for a portion of these equivocal results is the failure of some studies to achieve the level of body water loss (.3%) associated with diminished anaerobic performance (23,45). ...
... In a review, Kraft et al. (23) points out that it is difficult to determine the exact effects of hypohydration on anaerobic performance because of variations in exercise mode, mode of dehydration, and levels of hypohydration, among previous studies. Tests of anaerobic performance include one-repetition maximum weight lifting (14,30), full-body resistance exercise protocol (21), repeated back squats (18,21), unilateral leg extensions (14), vertical jump (7,14,18,44), 15-second Wingate tests (6,22), 30-second lower-body Wingate tests, and 30-second upper-body Wingate tests (16). In addition, various assessments of reaction time and skill (2,3,31,35,36) have been assessed. ...
... In a review, Kraft et al. (23) points out that it is difficult to determine the exact effects of hypohydration on anaerobic performance because of variations in exercise mode, mode of dehydration, and levels of hypohydration, among previous studies. Tests of anaerobic performance include one-repetition maximum weight lifting (14,30), full-body resistance exercise protocol (21), repeated back squats (18,21), unilateral leg extensions (14), vertical jump (7,14,18,44), 15-second Wingate tests (6,22), 30-second lower-body Wingate tests, and 30-second upper-body Wingate tests (16). In addition, various assessments of reaction time and skill (2,3,31,35,36) have been assessed. ...
Article
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This study examined effects of hypohydration on repeated 40 yard sprint performance. Anaerobically fit current and former Division II male athletes (n = 12) completed 2 bouts of 10 x 40 yard sprints followed by an agility test (AT), dehydrated (∼3% body weight(DT)), or euhydrated (HT). Statistical analysis of group means indicated that hypohydration had little effect on sprint times for either the first (DT: = 5.38 ± 0.37; HT = 5.35 ± 0.34) or second (DT = 5.47 ± 0.39; HT = 5.42 ± 0.39) bout of 10 sprints with only sprint number 2, 5, and 6 of bout 2 reaching statistical significance. However, when individual sprint performance was considered, a greater effect was seen. In all 83% (10 of 12) of subjects experienced a meaningful change (≥ 0.1 s) (positive or negative) in mean sprint time (DT vs. HT) for one or more bout of 10 sprints. RPE was significantly higher (∼ 1 unit on a 10 point scale) for DT in all sprints during bout 1 and the first 2 sprints of bout 2. These results indicate that the effect of hypohydration on repeated sprint performance varies among individuals. Some improved performance with hypohydration, while others experienced detrimental effects. Hypohydration also resulted in a particularly notable negative impact on perceptual measures of exertion even when performance was similar.
... 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. ...
... 2.4.2). Of all 28 manuscripts, only seven made it clear that participants voided their bladders prior to BW measurements before and after the dehydration protocol [8,11,20,25,38,42,43]. No study mentioned controlling for fecal loss during the experiments. ...
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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.
... Haff et al. 25 increased performance through sports drink intake before and during a one-hour session with 16 sets of 10 repetitions involving isokinetic exercise of the hamstrings and quadriceps. In Kraft 26 , 3% dehydration prior to strength training consisting of 3 sets at an intensity of 12 RM to failure and 2 minutes rest between sets, with exercises involving the whole body (bench press, lateral pulldown, military press, bicep curl, tricep extension and leg press), led to significantly fewer repetitions. Therefore, adequate hydration can increase the work performed during training sessions, because the right kind of drink is consumed and dehydration is prevented. ...
... In contrast, in Kraft et al's aforementioned study 26 , the RPE of the group which was dehydrated to 3% body mass significantly increased. These data do not coincide with those from this research, possibly because the body mass loss percentage in HAB (0.44±0.22%) was not as high as in this study. ...
Article
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Introduction: Male artistic gymnastics is a sport practiced individually with 6 different apparatus. It is a modality of high intensity and impact. Adequate hydration is important to avoid a decrease in performance and to reduce the risk of fatigue injuries. Material and method: The hydration patterns of the Spanish artistic gymnastics team are analyzed during training, their individual liquid requirements are calculated, and a personalized hydration is prescribed, with the aim of improve performance. In the research, 9 male elite gymnasts participated. Each one completed 2 equal workouts separated by one week; the first with his usual hydration pattern (HAB) and the second one with an individualized hydration, according to the calculation of their needs with sport drink (POW). All were weighed, and measured the specific gravity and osmolality of urine, before and after training; At the end of each session a rated perceived exertion questionnaire (RPE) was passed and a performance test was carried out. Results: It is observed that: i) POW significantly increased the drink intake in comparison to HAB during training (HAB: 0.57 ± 0.2 L, POW: 0.90 ± 0.2 L), ii) POW increased the number of pull-ups and total repetitions (HAB: 67.13 ± 4.9 repetitions, POW: 72.63 ± 5.7 repetitions), iii) HAB reduced body mass significantly after training iv) POW presented lower values of urine specific gravity after training and the% of body mass lost was negligible (HAB: 0.44 ± 0.2%, POW: 0.01 ± 0.1%), v) There were no differences in the urine osmolality, the PSE, the number of repetitions in hanging pikes and handstand push-ups between HAB and POW. Conclusion: Individualized hydration for each athlete with the appropriate drink improves performance during training.
... At present, a specific recommendation for an optimum rate or timing of carbohydrate ingestion for strength-power athletes before and during any given training session cannot be determined. As with all athletes, strength-power athletes should be encouraged to initiate training in a euhydrated state given that even moderate hypohydration can impair resistance-training work capacity ( Kraft et al., 2010). ...
Article
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Strength and power athletes are primarily interested in enhancing power relative to body weight and thus almost all undertake some form of resistance training. While athletes may periodically attempt to promote skeletal muscle hypertrophy, key nutritional issues are broader than those pertinent to hypertrophy and include an appreciation of the sports supplement industry, the strategic timing of nutrient intake to maximize fuelling and recovery objectives, plus achievement of pre-competition body mass requirements. Total energy and macronutrient intakes of strength-power athletes are generally high but intakes tend to be unremarkable when expressed relative to body mass. Greater insight into optimization of dietary intake to achieve nutrition-related goals would be achieved from assessment of nutrient distribution over the day, especially intake before, during, and after exercise. This information is not readily available on strength-power athletes and research is warranted. There is a general void of scientific investigation relating specifically to this unique group of athletes. Until this is resolved, sports nutrition recommendations for strength-power athletes should be directed at the individual athlete, focusing on their specific nutrition-related goals, with an emphasis on the nutritional support of training.
... Maintaining hydration status is considered important for sports performance as well as physical well-being. Neural, hormonal, metabolic and mechanical aspects involved in any physical training including sprint training are greatly influenced by the level of fluid available in the body (Kraft, et al., 2010). Fluid or water plays a fundamental role in the body as it functions as the solvents for nutrients, transport of nutrients to muscle cells, helps body eliminates waste products, maintenance of constant body temperature and protection of the fetus during pregnancy (Armstrong, 2007;Sawka, et al., 2007). ...
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The aim of this study to investigate the relationships among hydration status level, sprint time performance capabilities and physiological responses [blood pressure, heart rate and rate of perceived exertion (RPE)] during a 15m Repeated Sprint Ability (RSA) training session. Fifteen male participants with a mean age 21 ± 1 years old, total mean body weight of 63.21 ± 8.25kg, and mean body height of 1.68 ± 0.05m voluntarily participated in this study. The participants underwent an RSA session with all measurements of interest were conducted pre, during and post session. Paired sample t-test was used to analyse the hydration status (urine specific gravity), with repeated measure ANOVA was used to compared the sprint time and physiological responses. Pearson correlation was utilised to determine the relationship between hydration status, sprint time, heart rate response, blood pressure and RPE during the training session. The results indicated no significant changes in hydration status. However, there was a significant difference in body mass loss before and after the training. Sprint time performance indicated no significant differences between all sets involved, indicating steady state sprint performance. The physiological responses showed a significance increase during this 15m sprint training. Correlation values for sprint time and RPE versus hydration status demonstrate a significant and strong linear relationship. As a conclusion, 15m RSA for 3 sets of 5 repetitions have no significant effects on hydration status, with sprint time performance are not influenced by hydration during an RSA session. However, as participants trying to maintain sprint time performance, physical stress do increase and thus making it difficult to improves sprint time performance. Further studies on muscle metabolic factors are suggested for future research works.
... Furthermore, the reduction in body mass associated with hypohydration may reduce the work required to accelerate the body, compensating for any reduction in muscular strength/power (Maughan & Shirreffs, 2010). Despite this, longer duration activities undertaken by sprint athletes such as resistance training are impaired by hypohydration (Kraft et al., 2010). On the weight of this evidence, track-sprinting performance does not appear to be influenced by a state of hypohydration within the range of 2-3%, especially among trained individuals (Savoie et al., 2015). ...
Article
Although sprint athletes are assumed to primarily be interested in promoting muscle hypertrophy, it is the ability to generate explosive muscle power, optimization of power-to-weight ratio, and enhancement of anaerobic energy generation that are key outcomes of sprint training. This reflects the physique of track sprinters, being characterized as ecto-mesomorphs. Although there is little contemporary data on sprinters dietary habits, given their moderate energy requirements relative to body mass, a carbohydrate intake within the range of 3-6 g·kg-1·day-1 appears reasonable, while ensuring carbohydrate availability is optimized around training. Similarly, although protein needs may be twice general population recommendations, sprint athletes should consume meals containing ∼0.4 g/kg high biological value protein (i.e., easily digested, rich in essential amino acids) every 3-5 hr. Despite the short duration of competitions and relative long-recovery periods between races, nutrition still plays an important role in sprint performance. As energy expenditure moderates during competition, so too should intake of energy and macronutrients to prevent unwanted weight gain. Further adjustments in macronutrient intake may be warranted among athletes contemplating optimization of power-to-weight ratio through reductions in body fat prior to the competitive season. Other novel acute methods of weight loss have also been proposed to enhance power-to-weight ratio, but their implementation should only be considered under professional guidance. Given the metabolic demands of sprinting, a few supplements may be of benefit to athletes in training and/or competition. Their use in competition should be preceded with trialing in training to confirm tolerance and perceived ergogenic potential.
... Many of the exercises incorporated in a XF workout of the day (WOD) require repeated maximum effort or completion of technical movements. Dehydration has been found to impair performance during traditional resistance training (14,15) and impair motor control (2,10) which may be critical when completing repeated Olympic style lifts. Akin to the repetitive high intensity whole body exercise activities in XF, two recent studies also found decreased performance and increased heart rate and rate of perceived exertion during repeated 40-yard dash efforts in trained sprint-sport athletes (9,11). ...
Article
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This study assessed 30 male and 20 female well-trained CrossFit (XF) athletes’ natural hydration statuses, fluid intake, and absolute and estimated sweat losses during training sessions lasting 30-47 min. Participants provided a pre-workout urine sample for assessment of hydration by urine specific gravity (USG). Nude pre- and post-workout body mass and fluid intakes were measured to determine sweat losses. To evaluate perception of total sweat loss, participants were asked to estimate their total sweat loss to compare against actual sweat loss. Mean sweat losses did not exceed 1% body mass for men (range = 0.31-1.58% body mass) or women (range = 0.53-1.34% body mass), but sweat rates were nearly double for men (1.663 ± 0.478 L/h) vs. women (0.886 ± 0.274 L/h). Preexercise USG indicated euhydration for the majority of participants (32/50 samples = USG < 1.020). Only one participant had a USG >1.030. Mean sweat loss (0.746 ± 0.305 L) and mean sweat loss prediction (0.655 ± 0.404 L) were not significantly different (p = 0.12), and accuracy did not differ (p = 0.44) between men (-9.5 ± 53.7%) and women (+4.3 ± 70.9). No relationship (r = 0.095) was found between sweat loss prediction and fluid intake. Despite high sweat rates, no athletes lost greater than 2% body mass during a strenuous workout. This data combined with consistently normal pre-exercise USG and high fluid intake during exercise suggests ad libitum fluid intake is sufficient to ensure euhydration in the majority of XF participants.
... To allow for transferring conclusions from laboratory-based research to real-life settings, the study design should simulate real life as much as possible (i.e., the external or ecologic validity of the study). One difference between many laboratory studies and real-life settings is that the majority of studies [20][21][22][23][27][28][29][30][31]33,35,[38][39][40][42][43][44][45][47][48][49][50][51][52][53][54][56][57][58]61,62,66,67,[69][70][71]73,77,82,84,86] induced dehydration before exercise, either by exercising the subject in the heat, imposing fluid restrictions of about one to two days, or administering diuretic drugs before the exercise task. This is in contrast to real life, where athletes dehydrate during exercise (exercise-induced dehydration). ...
... Therefore, an alternative view of heat-induced hypo-hydration is proposed as: (a) central drive may be enhanced via reduced cortical inhibition or increased cortical facilitation, in an attempt to compensate for potential force decrements when hypo-hydrated but, (b) this may not be sufficient, particularly during sustained and repeated voluntary contractions where contractile function is impaired (Todd et al. 2005). This may explain why heat-induced hypo-hydration is notably reported to have 'no effect' on brief measures of power and strength (Jacobs 1980;Hoffman et al. 1995;Cheuvront et al. 2006;Watson et al. 2005;Periard et al. 2012;Greiwe et al. 1998;Montain et al. 1998;Evetovich et al. 2002), but consistently impairs performance during repeated or sustained contractions (Bigard et al. 2001;Maxwell et al. 1999;Mohr et al. 2010;Judelsen et al. 2007;Kraft et al. 2010;Periard et al. 2012;Bosco et al. 1968;Torranin et al. 1979;Schofstall et al. 2001). Further studies are required to elucidate the facilitatory and inhibitory responses (in the corticospinal pathway) to hypo-hydration. ...
Article
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Heat-induced hypo-hydration (hyperosmotic hypovolemia) can reduce prolonged skeletal muscle performance; however, the mechanisms are less well understood and the reported effects on all aspects of neuromuscular function and brief maximal contractions are inconsistent. Historically, a 4-6% reduction of body mass has not been considered to impair muscle function in humans, as determined by muscle torque, membrane excitability and peak power production. With the development of magnetic resonance imaging and neurophysiological techniques, such as electromyography, peripheral nerve, and transcra-nial magnetic stimulation (TMS), the integrity of the brain-to-muscle pathway can be further investigated. The findings of this review demonstrate that heat-induced hypo-hydration impairs neuromuscular function, particularly during repeated and sustained contractions. Additionally, the mechanisms are separate to those of hyperthermia-induced fatigue and are likely a result of modulations to corticospinal inhibition, increased fibre conduction velocity, pain perception and impaired contrac-tile function. This review also sheds light on the view that hypo-hydration has 'no effect' on neuromuscular function during brief maximal voluntary contractions. It is hypothesised that irrespective of unchanged force, compensatory reductions in cortical inhibition are likely to occur, in the attempt of achieving adequate force production. Studies using single-pulse TMS have shown that hypo-hydration can reduce maximal isometric and eccentric force, despite a reduction in cortical inhibition, but the cause of this is currently unclear. Future work should investigate the intracortical inhibitory and excitatory pathways within the brain, to elucidate the role of the central nervous system in force output, following heat-induced hypo-hydration.
... Perceptual measures efficacy in resistance training paradigms have received relatively less consideration than for intermittent high intensity sport or endurance type exercise. For example, Impellizzeri et al. (7) concluded that session-RPE is a good (12). Although more repetitions were completed for all LTC between 48 versus 24 h, and general trends of lower RPE were observed at 48h, particularly for MJ vs. SJ, no statistical differences were exhibited for RPE. ...
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International Journal of Exercise Science 8(1) : 85-96, 2015. This study examined muscle recovery patterns between single-joint (SJ) versus multi-joint (MJ), and upper-body (UB) versus lower-body (LB) exercises and the utility of perceptual measures (ratings of perceived exertion (RPE) and perceived recovery scale (PRS)) to assess recovery status. A 10 rep max (10-RM) was determined for 6 SJ and 4 MJ exercises (5 UB and 5 LB) for male recreational weightlifters (n = 10). Participants completed a baseline protocol including 8 repetitions at 85% of 10-RM followed by a set to failure with 100% of 10-RM. In a counterbalanced crossover design, participants returned at 24 or 48 h to repeat the protocol. PRS and RPE were assessed following the first and second sets of each exercise respectively. Wilcoxon matched pair signed-rank tests determined performance improved (p < 0.05) for every lift type category from 24 to 48 h, but the only difference in ∆ repetitions from baseline at the same time point was between MJ (-1.7 ± 1.5 repetitions) and SJ (-0.5 ± 1.8 repetitions) at 24 h (p = 0.037). Higher RPE and lower PRS estimations (p < 0.05) support the utility of perceptual measures to gauge recovery as the only between group differences were also found between MJ and SJ at 24 h. Eighty percent of participants completed within 1 repetition of baseline for all exercises at 48 h except bench press (70%) and deadlift (60%); suggesting 72 h of recovery should be implemented for multi-joint barbell lifts targeting the same muscle groups in slower recovering lifters.
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We examined hormonal and haematological parameters and the profile of mood states (POMS) in top level judoists undertaking a 7-week competitive training period in a real contest. Participants were 10 top level judoists belonging to the Spanish National Team. Training load was calculated by multiplying the training session intensity by the duration of the training session. The judoists competed in two official events on weeks 3 and 6 of the study. Urinary catecholamines increased at the end of the competitive period. Serum cortisol increased during the weeks in which judoists competed, confirming the existence of and anticipatory cortisol response to exercise; although we failed to find serum testosterone increases. Because of leukocyte values did not change, except monocytes, we speculate that the intensity of training was not sufficiently high to evoke injury to muscle tissue. Anger, tension, and fatigue increased according with training load, suggesting that the training exercise led participants into a negative psychological state. Findings indicate that during competitive periods, judoists suffer hormonal and mood changes according to training load and competitive events. Results support the usefulness of monitoring biological and psychological markers during season in order to adjust training loads and periods of recovery.
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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.
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Aerobic exercise capacity is tightly related to the ability of the cardiovascular system to bring enough oxygen to active muscles. This chapter first focuses on skeletal muscle blood flow control and presents its responses to acute and chronic exercise with a particular emphasis on the role of the active muscle mass and environmental factors. The second part describes how blood rheology impacts on the regulation of blood flow and vascular function. The effects of acute and chronic exercise on blood rheology are then discussed including blood viscosity, red blood cell deformability and aggregation. The last part focuses on a selection of nutritional supplements considered to have an impact on the cardiovascular system, blood flow responses, blood rheology and ultimately exercise performance. We discuss how intermediates of the nitric oxide metabolism, anti-oxidants as well as minerals and trace elements could modulate blood flow and blood rheology, and improve endurance exercise performance.
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Objective. — Dehydration impairs aerobic performance but the influence of dehydration andrehydration on cycling peak power is contradictory. The purpose of the study was to evaluate both the influence of body dehydration and the influence of rehydration on the level of cycling peak power. Methods. — Cycling peak power (CPP) was measured 3 times in 12 healthy males: in baseline testing, next after dehydrating the body using passive heat exposure (sauna), and after thesauna, with simultaneous hydration (in random order). Results. — The level of total work, CPP and time to attain peak power were comparable with the dehydration (1.9% of body mass) during and after the sauna combined with the systematic replenishment of isotonic drinks, and was significantly (P < 0.05) higher (with the exception of the time to attain cycling peak power) in relation to the initial measurement. The absolute CPP increased about 20 W on average after dehydration, and 25 W on average after thesauna with rehydration. The relative cycling peak power significantly increased after dehydration (11.6 ± 0.6 W·kg-1) and after passive heat exposure with rehydration (11.6 ± 0.7 W·kg-1) in comparison to the initial level (11.2 ± 0.4 W·kg-1). Conclusion. — The present results suggest that CPP was not affected by body fluid balance alterations. The research results show that moderate dehydration does not impair cycling peakpower.
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Bodybuilding involves an intricate combination of training and dieting focused around periodic mesocycles to tailor time towards preparation and competition. In contrast to other muscle sports (such as weightlifting and powerlifting), bodybuilding competitors are judged on appearance (muscle size, definition and posing) as opposed to physical performance. Professional competitors achieve this by altering training variables (such as intensity and volume) as well as dietary and supplementation strategies throughout the 'season'. These mesocycles follow protocols based on a scientific literature, with the intention to achieve better results and preserve the health of each competitor. In order to achieve the long term improvements to health and skill-related components of fitness, a programme and strategy must be implemented that incorporates components of both dietary restriction as well as systematic variations to training and exercise selection. Because of the nature of body aesthetics and muscularity in bodybuilding, off-season training follows hypertrophic goals to increase muscular size. Increased caloric intake as well as increased training volume and intensity are the most common adaptations to a hypertrophic mesocycle. A positive energetic caloric balance (~10-20%) and high protein consumption provide necessary nutrients for muscle protein synthesis and energy storage and usage. During any cycle, weight gain and loss should not surpass 5% bodyweight per week to reduce the health concerns associated with rapid weight fluctuations. Current literature suggests that macronutrient intakes of protein 1.6-2.2 g•kg-1 •d-1 (25-30% TDC), carbohydrates 5-6 g•kg-1 •d-1 (50-60% TDC) and fat 1-1.5 g•kg-1 •d-1 (20-25% TDC) are suggested as optimal for professional bodybuilders to meet the physiological needs of an off-season mesocycle focusing on lean muscle gain. Bodybuilding • Nutrition • Hypertrophy • Performance • Physique
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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.
Chapter
While the specific nutritional requirements of the strength and power athlete are no doubt sport and athlete-specific, these athletes do have similar overall objectives when it comes to dietary needs: (i) maintain good health, (ii) provide energy for training and competition, (iii) support recovery and adaptation from training and competition, and (iv) safe and effective use of performance-enhancing substances. This chapter highlights what is known about current dietary practices of strength and power athletes, offer insight into how these athletes can optimize nutrition for performance, and identify areas of concern. The most prevalent drugs used by strength and power athletes are those that are intended to increase muscle mass and strength by increasing muscle protein synthesis and/or decreasing protein degradation, such as anabolic androgenic steroids. The chapter focuses on energy intake, macronutrient intake, and positive drug tests and product purity.
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Nutrition plays a number of important roles for sprint athletes. Sprint athletes will benefit from a greater focus on training nutrition given the metabolic demands of training far exceed those of competition. An emphasis should be placed on the strategic timing of nutrient intake before, during, and after exercise to assist sprinters in optimizing resistance training work capacity, recovery, and body composition. While it is often assumed that sprint athletes are primarily interested in promoting muscle hypertrophy, optimization of body composition demands consideration of the effect of any changes in physique traits on power-to-weight and biomechanical efficiency. Nutritional supplements remain very popular among sprinters and there is evidence to support the use of a small number of products to assist sprinters in the training and/or competition environment. However, as with any dietary intervention for sprinters, these need to be trialed in training to assess tolerance and likely individual performance response.
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Gann, JJ, Andre, TL, Gallucci, AR, and Willoughby, DS. Effects of hypohydration on muscular strength, endurance, and power in women. J Strength Cond Res XX(X): 000-000, 2020-The purpose of this study was to determine the effects of dehydration on muscular strength, endurance, power, and perceptual measures in resistance-trained women. Ten resistance-trained women completed 2 bouts of exercise (1 repetition maximum [1RM] for bench press and angled leg press followed by 5 sets to failure of 75% of 1RM and vertical jump), either dehydrated (∼3% body mass) (DT) or heat-exposed with fluid replacement (HT). Paired t-tests revealed bench press 1RM was significantly lower for DT (42.7 ± 14.5 kg) compared with HT (44.1 ± 13.9 kg). No significant difference was found for leg press 1RM (DT = 216.1 ± 55.0 kg; HT = 223.4 ± 55.7 kg). There was also no difference in total reps completed for bench press (DT = 33.5 ± 5.0; HT = 33.0 ± 5.5) or leg press (DT = 42.6 ± 20.3; HT = 45.8 ± 19.7). There was no significant difference for vertical jump height (DT: 45.8 ± 5.2 cm, HT: 46.9 ± 6.0 cm). Ratings of perceived exertion (RPE) and session RPE were not significantly different between trials. Significant differences for perceived recovery status (DT: 5.1 ± 2.2, HT: 7.2 ± 1.1) and perceived readiness (DT: 4.2 ± 1.0, HT: 2.5 ± 0.5) indicate subjects expected impaired performance during DT. The current results suggest that previous night dehydration may have a negative impact on both bench press 1RM performance and perceptual feelings of recovery in resistance-trained women.
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Kwan, K and Helms, E. Prevalence, magnitude, and methods of weight cutting used by world class powerlifters. J Strength Cond Res 36(4): 998-1002, 2022-Powerlifters compete in the squat, bench press, and deadlift, with winners determined by the highest 3-lift total in each weight class. As a weight class-based sport, athletes often compete in classes lower than their habitual weight, using various strategies to make weight. This study's purpose was to examine weight cutting prevalence, magnitude, and methods among 42 male and 22 female powerlifters (25 ± 8 years old; 4 ± 2.2 years of competitive experience) competing at the 2018 International Powerlifting Federation classic world championship. The lifters, 83% of whom cut weight losing an average 2.9 ± 4.3% of body mass, completed a previously validated weight cutting questionnaire. The most frequently used weight cutting methods were gradual dieting (42.18%, 31.25%), fluid restriction after fluid loading (32.8%, 34.4%), restricting fluid ingestion without fluid loading (23.4%, 9.4%), fasting (15.6%, 18.7%), increased activity (9.4%, 24.4%), laxatives (9.4%, 18.7%), sauna (7.8%, 6.3%), diuretics (7.8%, 6.3%), skipping meals (4.7%, 21.9%), and wearing rubber suits (1.6%, 2.6%). Most lifters experienced negative changes in psychological state, with only 9% reporting never experiencing any negative effect on psychological state across the 5 states measured. Lifters reported experiencing fatigue (15.6%, 45.3%), anger (3.2%, 26.6%), feelings of isolation (4.7%, 12.5%), and anxiety (14.1%, 35.95%), and 11 of the 12 lifters who reported a perceived decrement in training performance performed weight cutting. Both weight cutting methods and negative psychological changes experienced were reported as always, sometimes. Therefore, it is vital to provide specific recommendations based on scientific research to improve the efficacy and safety of making weight while minimizing performance decrements.
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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.
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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.
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The regulation of the active form of pyruvate dehydrogenase (PDHa) and related metabolic events were examined in human skeletal muscle during repeated bouts of maximum exercise. Seven subjects completed three consecutive 30-s bouts of maximum isokinetic cycling, separated by 4 min of recovery. Biopsies of the vastus lateralis were taken before and immediately after each bout. PDHa increased from 0.45 +/- 0.15 to 2.96 +/- 0.38, 1.10 +/- 0.11 to 2.91 +/- 0.11, and 1.28 +/- 0.18 to 2.82 +/- 0.32 mmol.min-1.kg wet wt-1 during bouts 1, 2, and 3, respectively. Glycolytic flux was 13-fold greater than PDHa in bouts 1 and 2 and 4-fold greater during bout 3. This discrepancy between the rate of pyruvate production and oxidation resulted in substantial lactate accumulation to 89.5 +/- 11.6 in bout 1, 130.8 +/- 13.8 in bout 2, and 106.6 +/- 10.1 mmol/kg dry wt in bout 3. These events coincided with an increase in the mitochondrial oxidation state, as reflected by a fall in mitochondrial NADH/NAD, indicating that muscle lactate production during exercise was not an O2-dependent process in our subjects. During exercise the primary factor regulating PDHa transformation was probably intracellular Ca2+. In contrast, the primary regulatory factors causing greater PDHa during recovery were lower ATP/ADP and NADH/NAD and increased concentrations of pyruvate and H+. Greater PDHa during recovery facilitated continued oxidation of the lactate load between exercise bouts.
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This study examined the effect of high intensity, moderate duration (40 min) exercise and water restriction on anaerobic power, vertical jumping height, and basketball shooting performance. Ten healthy male basketball players participated in two simulated '2 on 2 full-court' basketball games. Water consumption was permitted in one game (Wa) but not in the other (NWa), in a balanced cross-over design. Subjects began each game euhydrated. All jump tests (squat jump, counter movement jump, and 30 second jump test) were performed prior to, at half-time, and immediately following each game (POST). Performance was measured by both field goal (FG%) and free throw (FT%) percentages recorded during each half. Players incurred a -1.9 +/- 0.4% body weight loss during NWa. No significant differences were observed between WA and NWa in anaerobic power, squat jump, or counter movement jump. However, a 19% difference in anaerobic power (p > 0.05) was observed between Wa (36.1 +/- 4.8 W.kg-1) and NWa (30.4 +/- 6.6 W.kg-1) at POST. No significant differences were observed between Wa and NWa in both FG% and FT% however, an 8.1% decrease (p > 0.05) in FG% was seen between the first and second half during NWa. Although the decreases in anaerobic power and FG% did not reach significance, the results suggest that the combination of high intensity, moderate duration exercise, and fluid restriction might be detrimental to performance.
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To examine the importance of phosphocreatine (PCr) degradation in maintaining power output during maximal intermittent cycling, seven healthy men completed three bouts of isokinetic cycling (30 s, 100 revolutions/min) with 4 min of rest between bouts. After bout 2, blood flow to one leg was occluded by cuffing the thigh (Cuff) during the rest period to prevent PCr resynthesis while the circulation to the other leg was intact (Cont). The cuff was then removed and bout 3 completed. Muscle biopsies were sampled from the vastus lateralis of both legs just before and immediately after bout 3. Total work produced by the Cuff and Cont legs was similar during bouts 1 (9.3 +/- 0.5 and 9.6 +/- 0.5 kJ, respectively) and 2 (8.1 +/- 0.4 and 8.3 +/- kJ, respectively). Cuffing prevented the resynthesis of PCr because pre-bout 3 contents were 20.7 +/- 8.4 and 63.0 +/- 3.3 mmol/kg dry muscle in the Cuff and Cont legs, respectively. Cuffing also resulted in significantly higher muscle levels of lactate, H+ concentration (287 +/- 26 vs. 217 +/- 15 nM), ADP, AMP, and acetyl-CoA before bout 3 but had no effect on other glycolytic intermediates, ATP, or acetylcarnitine. Total work in bout 3 was significantly reduced by 15% in the Cuff leg (5.8 +/- 0.4 vs. 6.8 +/- 0.6 kJ). PCr degradation during bout 3 was 3.1 and 47.5 mmol/kg dry muscle in the Cuff and Cont legs, respectively, and lactate accumulation was minimal in both legs. Changes in all other metabolites during bout 3 were not different between legs. The results suggest that PCr contributed approximately 15% of the total ATP provision during the third 30-s bout of maximal isokinetic cycling and that most of the ATP was provided during the initial 15 s. Muscle glycogenolysis contributed minimally to ATP provision (approximately 10-15%) during the third 30-s bout, suggesting that aerobic metabolism becomes the dominant source of ATP during this model of repeated sprinting.
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This study examined the contribution of phosphocreatine (PCr) and aerobic metabolism during repeated bouts of sprint exercise. Eight male subjects performed two cycle ergometer sprints separated by 4 min of recovery during two separate main trials. Sprint 1 lasted 30 s during both main trials, whereas sprint 2 lasted either 10 or 30 s. Muscle biopsies were obtained at rest, immediately after the first 30-s sprint, after 3.8 min of recovery, and after the second 10-and 30-s sprints. At the end of sprint 1, PCr was 16.9 ± 1.4% of the resting value, and muscle pH dropped to 6.69 ± 0.02. After 3.8 min of recovery, muscle pH remained unchanged (6.80 ± 0.03), but PCr was resynthesized to 78.7 ± 3.3% of the resting value. PCr during sprint 2 was almost completely utilized in the first 10 s and remained unchanged thereafter. High correlations were found between the percentage of PCr resynthesis and the percentage recovery of power output and pedaling speed during the initial 10 s of sprint 2 (r = 0.84, P < 0.05 and r = 0.91, P < 0.01). The anaerobic ATP turnover, as calculated from changes in ATP, PCr, and lactate, was 235 ± 9 mmol/kg dry muscle during the first sprint but was decreased to 139 ± 7 mmol/kg dry muscle during the second 30-s sprint, mainly as a result of a ~45% decrease in glycolysis. Despite this ~41% reduction in anaerobic energy, the total work done during the second 30-s sprint was reduced by only ~18%. This mismatch between anaerobic energy release and power output during sprint 2 was partly compensated for by an increased contribution of aerobic metabolism, as calculated from the increase in oxygen uptake during sprint 2 (2.68 ± 0.10 vs. 3.17 ± 0.13 l/min; sprint 1 vs. sprint 2; P < 0.01). These data suggest that aerobic metabolism provides a significant part (~49%) of the energy during the second sprint, whereas PCr availability is important for high power output during the initial 10 s.
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The crucial role of muscle glycogen as a fuel during prolonged exercise is well established, and the effects of acute changes in dietary carbohydrate intake on muscle glycogen content and on endurance capacity are equally well known. More recently, it has been recognized that diet can also affect the performance of high-intensity exercise of short (2-7 min) duration. If the muscle glycogen content is lowered by prolonged (1-1.5 h) exhausting cycle exercise, and is subsequently kept low for 3-4 days by consumption of a diet deficient in carbohydrate (< 5% of total energy intake), there is a dramatic (approximately 10-30%) reduction in exercise capacity during cycling sustainable for about 5 min. The same effect is observed if exercise is preceded by 3-4 days on a carbohydrate-restricted diet or by a 24 h total fast without prior depletion of the muscle glycogen. Consumption of a diet high in carbohydrate (70% of total energy intake from carbohydrate) for 3-4 days before exercise improves exercise capacity during high-intensity exercise, although this effect is less consistent. The blood lactate concentration is always lower at the point of fatigue after a diet low in carbohydrate and higher after a diet high in carbohydrate than after a normal diet. Even when the duration of the exercise task is kept constant, the blood lactate concentration is higher after exercise on a diet high in carbohydrate than on a diet low in carbohydrate. Consumption of a low-carbohydrate isoenergetic diet is achieved by an increased intake of protein and fat. A high-protein diet, particularly when combined with a low carbohydrate intake, results in metabolic acidosis, which ensues within 24 h and persists for at least 4 days. This appears to be the result of an increase in the circulating concentrations of strong organic acids, particularly free fatty acids and 3-hydroxybutyrate, together with an increase in the total plasma protein concentration. This acidosis, rather than any decrease in the muscle glycogen content, may be responsible for the reduced exercise capacity in high-intensity exercise; this may be due to a reduced rate of efflux of lactate and hydrogen ions from the working muscles. Alternatively, the accumulation of acetyl groups in the carbohydrate-deprived state may reduce substrate flux through the pyruvate dehydrogenase complex, thus reducing aerobic energy supply and accelerating the onset of fatigue.
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It is the position of the American College of Sports Medicine that adequate fluid replacement helps maintain hydration and, therefore, promotes the health, safety, and optimal physical performance of individuals participating in regular physical activity. This position statement is based on a comprehensive review and interpretation of scientific literature concerning the influence of fluid replacement on exercise performance and the risk of thermal injury associated with dehydration and hyperthermia. Based on available evidence, the American College of Sports Medicine makes the following general recommendations on the amount and composition of fluid that should be ingested in preparation for, during, and after exercise or athletic competition: 1) It is recommended that individuals consume a nutritionally balanced diet and drink adequate fluids during the 24-hr period before an event, especially during the period that includes the meal prior to exercise, to promote proper hydration before exercise or competition. 2) It is recommended that individuals drink about 500 ml (about 17 ounces) of fluid about 2 h before exercise to promote adequate hydration and allow time for excretion of excess ingested water. 3) During exercise, athletes should start drinking early and at regular intervals in an attempt to consume fluids at a rate sufficient to replace all the water lost through sweating (i.e., body weight loss), or consume the maximal amount that can be tolerated. 4) It is recommended that ingested fluids be cooler than ambient temperature [between 15 degrees and 22 degrees C (59 degrees and 72 degrees F])] and flavored to enhance palatability and promote fluid replacement. Fluids should be readily available and served in containers that allow adequate volumes to be ingested with ease and with minimal interruption of exercise. 5) Addition of proper amounts of carbohydrates and/or electrolytes to a fluid replacement solution is recommended for exercise events of duration greater than 1 h since it does not significantly impair water delivery to the body and may enhance performance. During exercise lasting less than 1 h, there is little evidence of physiological or physical performance differences between consuming a carbohydrate-electrolyte drink and plain water. 6) During intense exercise lasting longer than 1 h, it is recommended that carbohydrates be ingested at a rate of 30-60 g.h(-1) to maintain oxidation of carbohydrates and delay fatigue. This rate of carbohydrate intake can be achieved without compromising fluid delivery by drinking 600-1200 ml.h(-1) of solutions containing 4%-8% carbohydrates (g.100 ml(-1)). The carbohydrates can be sugars (glucose or sucrose) or starch (e.g., maltodextrin). 7) Inclusion of sodium (0.5-0.7 g.1(-1) of water) in the rehydration solution ingested during exercise lasting longer than 1 h is recommended since it may be advantageous in enhancing palatability, promoting fluid retention, and possibly preventing hyponatremia in certain individuals who drink excessive quantities of fluid. There is little physiological basis for the presence of sodium in n oral rehydration solution for enhancing intestinal water absorption as long as sodium is sufficiently available from the previous meal.
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The purpose of this study was to determine whether hypohydration reduces skeletal muscle endurance and whether increased H+ and Pi might contribute to performance degradation. Ten physically active volunteers (age 21-40 yr) performed supine single-leg, knee-extension exercise to exhaustion in a 1.5-T whole body magnetic resonance spectroscopy (MRS) system when euhydrated and when hypohydrated (4% body wt). 31P spectra were collected at a rate of one per second at rest, exercise, and recovery, and were grouped and averaged to represent 10-s intervals. The desired hydration level was achieved by having the subjects perform 2-3 h of exercise in a warm room (40 degrees C dry bulb, 20% relative humidity) with or without fluid replacement 3-8 h before the experiment. Time to fatigue was reduced (P < 0.05) by 15% when the subjects were hypohydrated [213 +/- 12 vs. 251 +/- 15 (SE) s]. Muscle strength was generally not affected by hypohydration. Muscle pH and Pi/beta-ATP ratio were similar during exercise and at exhaustion, regardless of hydration state. The time constants for phosphocreatine recovery were also similar between trials. In summary, moderate hypohydration reduces muscle endurance, and neither H+ nor Pi concentration appears to be related to these reductions.
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Purpose: The purpose of this investigation was to examine the weight management (WM) behaviors of collegiate wrestlers after the implementation of the NCAA's new weight control rules. Methods: In the fall of 1999, a survey was distributed to 47 college wrestling teams stratified by collegiate division (i.e., I, 11, 111) and competitive quality. Forty-three teams returned surveys for a total of 741 responses. Comparisons were made using the collegiate division, weight class, and the wrestler's competitive winning percentage. Results: The most weight lost during the season was 5.3 kg +/- 2.8 kg (mean +/- SD) or 6.9% +/- 4.7% of the wrestler's weight; weekly weight lost averaged 2.9 kg +/- 1.3 kg or 4.3% +/- 2.3% of the wrestler's weight; post-season, the average wrestler regained 5.5 kg +/- 3.6 kg or 8.6% +/- 5.4% of their weight. Coaches and fellow wrestlers were the primary influence on weight loss methods; however, 40.2% indicated that the new NCAA rules deterred extreme weight loss behaviors. The primary methods of weight loss reported were gradual dieting (79.4%) and increased exercise (75.2%). However, 54.8% fasted, 27.6% used saunas, and 26.7% used rubber/ plastic suits at least once a month. Cathartics and vomiting were seldom used to lose weight, and only 5 met three or more of the criteria for bulimia nervosa. WM behaviors were more extreme among freshmen, lighter weight classes, and Division 11 wrestlers. Compared to previous surveys of high school wrestlers, this cohort of wrestlers reported more extreme WM behaviors. However, compared to college wrestlers in the 1980s, weight loss behaviors were less extreme. Conclusions: The WM practices of college wrestlers appeared to have improved compared to wrestlers sampled previously. Forty percent of the wrestlers were influenced by the new NCAA rules and curbed their weight loss practices. Education is still needed, as some wrestlers are still engaging in dangerous WM methods.
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To assess the effects of rapid weight reduction, four university wrestlers decreased their body weight by 8% over a four-day period by food and liquid intake reductions. Significant decreases in muscle glycogen concentration and dynamic strength, but not aerobic or anaerobic capacity, accompanied weight loss. A three-hour rehydration period did not improve glycogen levels or strength performance. These results suggest that rapid weight reduction may impair wrestling performance.
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Physical work capacity was measured in a standard exercise test on a bicycle ergometer: 50% of VO2 max (maximal oxygen uptake) for 8 min, 70% for 5 min, and 105% until exhaustion. The amount of work performed in the last bout was used as an index of physical work capacity. The subjects performed the test under normal (control) conditions and after: prolonged (90-160 min) bicycle exercise (50% of VO2 max); passive heating in water until a rectal temperature of 38°C was achieved; sauna dehydration until body weight loss and rectal temperature were the same as after prolonged exercise; and after diuretic dehydration to the same weight loss as that obtained in the prolonged exercise. Heart rate, oxygen consumption, rectal and muscle temperatures, and weight loss were measured. Blood samples were taken for determinations of hematocrit, hemoglobin concentration, plasma levels of sodium, potassium and chloride, osmolarity, and blood lactate. It was concluded that the reduction in physical work capacity following prolonged exercise was the result of changes in many variables, partly the depletion of energy stores. However, dehydration and hyperthermia had separate effects in reducing work capacity. Electrolyte shifts and plasma volume changes were also associated with changes in work capacity. For all pretreatments taken together, the best indicator of physical work capacity was the difference between maximal heart rate and the heart rate obtained at 70% of VO2 max in the standard test.
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The activity patterns of many sports (e.g. badminton, basketball, soccer and squash) are intermittent in nature, consisting of repeated bouts of brief (≤-second) maximal/near-maximal work interspersed with relatively short (≤60-second) moderate/low-intensity recovery periods. Although this is a general description of the complex activity patterns experienced in such events, it currently provides the best means of directly assessing the physiological response to this type of exercise. During a single short (5- to 6-second) sprint, adenosine triphosphate (ATP) is resynthesised predominantly from anaerobic sources (phosphocreatine [PCr] degradation and glycolysis), with a small (
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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 ≈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.
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Dehydration by means of exercise, heat, diuretics, semistarvation, or a combination of these is common practice among competitors in weight class sports. Many studies have demonstrated a reduced aerobic work capacity following each of these forms of dehydration. The effects of these practices on performance that requires energy derived primarily from anaerobic sources is not well documented. The purpose of this study was to examine the effects of progressive, acute, thermal dehydration on performance of an anaerobic criterion task. Eleven collegiate wrestlers performed the Wingate Anaerobic Test (WAnT) prior to and after each of the following mean weight losses: 2%, 4%, and 5%. Weight loss was induced by passive thermal dehydration (56°C, 15% RH). Approximately 2 h were required in the environmental chamber to lose the required weight at each stage. There was no significant change (P > 0.05) in the ability to perform the WAnT or its various indices at any stage of dehydration, nor were blood lactate concentrations post WAnT significantly different from predehydration levels. This suggests that anaerobic performance may not be impaired to the extent that aerobic performance is by passive, thermal dehydration to a 5% body weight loss. However, deleterious physiologic effects may result from dehydration practices even though performance levels are maintained.
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Because of the continued prevalence of rapid weight reduction by wrestlers, this study attempted to determine if college wrestlers' strength and muscular endurance were affected by either rehydration or dehydration. Results showed that a loss of five percent of body weight over three days did not affect strength or endurance levels. (JMK)
Article
Purpose: This study measured the effects of sauna-induced dehydration (Dhy) and the effectiveness of rapid rehydration on muscle performance and EMG frequency spectrum changes associated with fatigue during isometric contractions. Methods: Knee extensor muscle strength during isometric maximal voluntary contraction (MVC) and endurance time at 25% and 70% of MVC (ET25 and ET70, respectively) were measured three times in 11 healthy male subjects, under euhydration conditions (Eu), after Dhy, and after rehydration following Dhy (Rhy). Results: Dhy led to a decrease in body weight by 2.95 +/- 0.05%. No significant effect of the hydration status was shown on MVC values. A 23% decrease in ET25 was recorded during Dhy (P < 0.01), whereas ET70 only tended to decrease (-13%, P = 0.06). ET25 was higher during Rhy than Dhy (8%, P < 0.05) but remained lower than during Eu (-17%, P < 0.05). The EMG root mean square (RMS) increased earlier during Dhy than Eu. Opposite changes were shown for the mean power frequency (MPF) of EMG, and Dhy resulted in an accelerated fall in MPF. However, because ET25 decreased with dehydration, RMS and MPF changes were similar during Eu and Dhy when reported to normalized contraction time, exhaustion was thus associated with similar values of RMS and MPF for all conditions. RMS and MPF changes during Rhy showed an intermediate pattern between Eu and Dhy. Conclusions: Dhy induced an increase in muscle fatigue, associated with early changes in EMG spectral parameters. It is not clear whether these alterations could be attributed to biochemical modifications, and the role of increased perception of effort when subjects were dehydrated should be clarified.
Article
This is the first study to demonstrate significant reductions in blood flow to exercising skeletal muscle during prolonged exercise in humans. Previous studies in humans (Kirwan et al. 1987; Nielsen et al. 1990, 1993, 1997), rats (Laughlin & Armstrong, 1983) and miniature swine (Armstrong et al. 1987; McKirnan et al. 1989) have shown that blood flow to active muscles is either maintained or increased when heat stress is superimposed during exercise. This is in contrast to the significant reductions in blood flow to some exercising muscles found in sheep with heat stress (Bell et al. 1983). The main reason for the discrepancy might be that the heat stress used in human and most animal studies did not reduce cardiac output unlike the present study with dehydration and Bell et al. (1983). In previous human studies from this laboratory, it was shown that muscle blood flow in the working leg was not reduced compared with control values when heat stress was imposed during prolonged walking (Nielsen et al. 1990), knee-extension exercise (Savard et al. 1988) or moderate- and high-intensity bicycling exercise in the semirecumbent position (Nielsen et al. 1993, 1997). In all studies, the cardiovascular system responded adequately to the additional demand of an elevated skin blood flow by increasing cardiac output (1–3 l min−1) and possibly reducing splanchnic and renal blood flow as shown by others (Rowell et al. 1965, 1971; Ho et al. 1997). Further support for unaltered muscle perfusion in these previous studies was found in the observations that femoral a-vO2 difference, leg V̇O2 and lactate release were unchanged (Savard et al. 1988; Nielsen et al. 1990, 1993, 1997). The present design used upright, moderately intense prolonged exercise in the heat with the aim of taxing the cardiovascular system to the extent where cardiac output declines markedly (Sawka et al. 1979; Montain & Coyle, 1992; González-Alonso et al. 1995).
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.
Article
Thesis (M.S.)--Old Dominion University, 1998. Includes bibliographical references.
Article
Thermal dehydration is a technique that is used frequently by wrestlers and jockeys to lose weight rapidly. This is done in order to qualify for competition in a lower weight classification. Despite occasional warnings of the potential dangers associated with rapid dehydration, there is somewhat incomplete research to guide athletes, coaches tainers, and physicians in an objective evaluation of the practice, either from the standpoint of the athlete's health or his physiological readiness to perform. The primary purpose of this study was to evaluate the effect of dehydration and subsequent rehydration on local muscular endurance during isometric and isotonic exercise. Twenty subjects, age 21-30 years, were randomly assigned to isometric and isotonic groups. Experimental subjects for isometric work served as controls for isotonic exercise, and vice versa. Muscular endurance time (ET) was evaluated at 75% of maximum voluntary contraction (MVC) at euhydration, after a weight loss of approximately 4%, and following full fluid replacement. Hand grip, arm curl, bench press, and leg press activities were investigated. Results revealed that following dehydration, muscular endurance time, averaged over all muscle groups, was significantly shorter during isometric (-31%) and isotonic (-29%) work. The results also suggested that dehydration decreased the endurance of some muscle groups more than others. After rehydration, isometric ET (-13%) and isotonic ET (-21%) were still significantly below predehydration levels. It was concluded that rapid, thermal dehydration is not a desirable practice for atheletes since it substantially decreases the isometric and insotonic endurance of skeletal muscles at 75% MVC. Further, four hours of rehydration is not sufficient time to restore these variables to control levels.
Article
There are at least 5 metabolic causes of fatigue, a decrease in the phosphocreatine level in muscle, proton accumulation in muscle, depletion of the glycogen store in muscle, hypoglycaemia and an increase in the plasma concentration ratio of free tryptophan/branched-chain amino acids. Proton accumulation may be a common cause of fatigue in most forms of exercise and may be an important factor in fatigue in those persons who are chronically physically inactive and also in the elderly: thus, the aerobic capacity markedly decreases under these conditions, so that ATP must be synthesized by the much less efficient anaerobic system. A marked increase in the plasma fatty acid level, which may occur when liver glycogen store is depleted and when hypoglycaemia results, or during intermittent exercise when the rate of fatty acid oxidation may not match the mobilisation of fatty acids, could be involved indirectly in fatigue. This is because such an increase in the plasma level of fatty acids raises the free plasma concentration of tryptophan, which can increase the entry of tryptophan into the brain, which will increase the brain level of 5-hydroxytryptamine: there is evidence that the latter may be involved in central fatigue. In this case, provision of branched-chain amino acids in order to maintain the resting plasma concentration ratio of free tryptophan/branched-chain amino acids should delay fatigue--there is prima facie evidence in support of this hypothesis. This hypothesis may have considerable clinical importance.
Article
This study was conducted to develop a testing protocol which would determine the extent of upper-body power output decrements in subjects following weight loss. Five athletes who had trained via upper-body exercise performed a 6-minute variable intensity arm crank test on an isokinetic ergometer before and after a 3-day, 4.5% body weight loss. Blood samples were drawn from a forearm vein pre- and 1, 3, and 5 min post-arm cranking for assessment of lactate, pH, hemoglobin, and hematocrit. The work performed pre-weight loss was significantly (paired t-test, p less than 0.05) greater than that performed post-weight loss. Repeated measures ANOVA yielded no significant differences in blood variables; however, pre-weight loss lactate values were higher and hemoglobin, hematocrit, and pH values were lower than post-weight loss values. It was concluded that a 4.5% body weight reduction resulted in performance decrements during this arm crank test. Survey information obtained from collegiate wrestlers (n = 14) subsequently tested under this protocol indicates the physical demands of this test approximate the physical demands of actual wrestling competition. It would therefore be appropriate to use this protocol during future testing of wrestlers in weight loss studies.
Article
Twelve competitive wrestlers restricted their caloric intake (92 kJ/kg FFW/day) for 7 days, using a high (HC) or normal (NC) carbohydrate diet to determine the acute effect of caloric deficiency on aerobic and anaerobic exercise performance as well as growth hormone (hGH) and insulin-like growth factor 1 (IGF-1) levels. The subjects were tested while on a eucaloric diet and at the end of the dietary restriction. Neither the dietary restriction nor composition had an effect on the ability to complete an 8-minute run at 85% of maximal capacity, but both produced an increased fat utilization during the run. The responses to the Wingate Anaerobic Test indicated that the NC group had a significant reduction in total and mean power output (-7% & -6%, respectively; p less than 0.05), whereas the HC group maintained all power measures. The caloric restriction, regardless of dietary composition, increased the exercise hGH response more for the NC group than the HC group (p less than 0.05). IGF-1 levels were significantly lowered by the diet, but the diet composition had no effect. These results indicate that even during caloric restriction, a high carbohydrate diet better maintains anerobic exercise performance. Furthermore, the composition of the diet appears to have no effect on the resting hGH and IGF-1 responses to caloric deficits. However, carbohydrate composition may have an effect on the gGH response to exercise.
Article
To assess current weight loss practices in wrestlers, 63 college wrestlers and 368 high school wrestlers completed a questionnaire that examined the frequency and magnitude of weight loss, weight control methods, emotions associated with weight loss, dieting patterns, and preoccupation with food. Clear patterns emerged showing frequent, rapid, and large weight loss and regain cycles. Of the college wrestlers, 41% reported weight fluctuations of 5.0-9.1 kg each week of the season. For the high school wrestlers, 23% lost 2.7-4.5 kg weekly. In the college cohort, 35% lost 0.5-4.5 kg over 100 times in their life, and 22% had lost 5.0-9.1 kg between 21 and 50 times in their life. Of the high school wrestlers, 42% had already lost 5.0-9.1 kg 1-5 times in their life. A variety of aggressive methods wer used to lose weight including dehydration, food restriction, fasting, and, for a few, vomiting, laxatives, and diuretics. "Making weight" was associated with fatigue, anger, and anxiety. Thirty to forty percent of the wrestlers, at both the high school and college level, reported being preoccupied with food and eating out of control after a match. The tradition of "making weight" still appears to be integral to wrestling. The potential physiological, psychological, and health consequences of these practices merit further attention.
Article
The effects of weight loss (dehydration) techniques (which mimicked techniques used prior to actual competition) used by intercollegiate wrestlers on selected physiological parameters (strength, anaerobic power, anaerobic capacity, the lactate threshold (LT), and peak aerobic power) were examined in seven intercollegiate wrestlers. During the 36 h weight loss period, subjects lost 3.3 kg (4.9% body weight), all of which occurred during the 12 h prior to weigh-in, using exercise in a rubberized sweat suit. Weight loss resulted in a reduction in upper body but not lower body strength measures (peak torque and average work per repetition). Anaerobic power and anaerobic capacity were significantly reduced in a dehydrated state (81.4 kgm.s-1, normal weight; 63.9 kgm.s-1, weight loss; 1984.3 kgm.40 s-1, normal weight; 1791.4 kgm.40 s-1, weight loss). Analyses of treadmill data revealed the following: 1) velocity was decreased at LT (4.4%) and peak (6.5%) during weight loss (P less than 0.05); 2) VO2 peak was significantly reduced with weight loss (6.7%, P less than 0.05); 3) treadmill time to exhaustion was significantly reduced in the weight loss state (12.4%) (35.7 min, normal weight; 31.3 min, weight loss). It was concluded that typical wrestling weight loss techniques result in deleterious effects on strength, anaerobic power, anaerobic capacity, the lactate threshold, and aerobic power.
Article
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.
Article
The effects of three weight reduction methods on maximal strength, rate of force development, vertical jumping height, and mechanical power were studied in track and field athletes and volleyball players. The three methods were sauna, diet with diuretic, and diuretic alone. The reductions in weight achieved were 3.4%, 5.8%, and 3.8% of body weight after sauna, diet + diuretic, and diuretic, respectively (P less than 0.001). Maximal isometric leg strength and the rate of isometric force development were decreased after the sauna and diet + diuretic treatments. Dehydration caused by the diuretic method alone did not impair neuromuscular performances. As had been expected from theoretical calculations, the rise of the body center of gravity in vertical jumping was slightly improved with all three treatments, the improvement being the greatest following the diuretic treatment (7.1%, P less than 0.001). However, when the work performed was extended for 15 s, an improved power output could be observed only with the diet + diuretic treatment (P less than 0.01). No explanation for the results observed could be made in terms of physiologic parameters.
Article
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.
Article
Observations on hematocrit (Hct) and hemoglobin (Hb) were made in 6 men before and after running long enough to cause a 4% decrease in body weight. Subscripts B and A were used to denote before dehydration and after dehydration, respectively. Relations were derived between BV(b), BV(a), HB(b), Hb(a), Hct(b), and Hct(a) with which the percentage decreases in BV, CV, and PV can be calculated, as well as the concentration of hemoglobin in red cells, g/100 ml-1 (MCHC). When subjects reach the same level of dehydration the water loss from the various body compartments may vary reflecting the difference in salt losses in sweat. Changes in PV calculated from the increase in plasma protein concentration averaged -7.5% compared with -12.2% calculated from changes in Hb and Hct. The difference could be accounted for by a loss of 6% plasma protein from the circulation.
Article
Eighteen girth, skinfold, cardiovascular, cable tension strength, and response time measurements were obtained in order to assess the effects of weight reduction on a group of college wrestlers. In 10 of the 18 measurements mean differences were found to be significant at the .05 level from the statistical analysis provided by a repeated measures analysis of variance. It was generally concluded that for the ten subjects studied up to 7 percent of body weight may be lost without adversely affecting factors apparently related to wrestling performance —strength, cardiovascular endurance, and response time.
Article
The physiological effects on submaximal and maximal exercise of three methods commonly used by athletes for achieving rapid weight loss were determined by measuring cardiorespiratory variables in 62 nonendurance athletes. A mean weight loss of 4.1% was achieved by those who followed either a sauna (SAU), diuretic (DIU), or exercise (ACT) protocol, compared with the average weight loss of 1.2% in the control group. At maximal exercise O2 consumption, O2 pulse, blood lactate concentration, and work load decreased in SAU and DIU groups relative to the ACT group, whereas only a few differences were observed at the aerobic threshold. Weight loss achieved over a 48-h period was less detrimental to an athlete than was a more rapid (24-h) weight reduction achieved through sauna bathing or the use of diuretics. We conclude that not only the quantity of weight loss but also the method itself may limit physical performance.
Article
A 21-yr-old male wrestler was studied for 2 months as he trained and dieted for the 1981 Maccabiah Games trials and the 1981 National AAU Wrestling Tournament trials. Measurements of body composition, anthropometry, pulmonary function, muscular strength, serum plasma constituents, and maximal aerobic power were made 53, 31, and 3 d prior to the AAU tournament. Training consisted of two workouts daily, running 3.2-9.7 km each morning and wrestling 1-2.5 h each afternoon. In addition, the subject recorded his weight daily and maintained a log of food consumption. As a result of a low-fat, high-protein, high-carbohydrate diet and continued training, his weight decreased from 54.88 to 50.59 kg while body fat decreased from 4.8 to 1.1%. This loss consisted of 2.21 kg of lean tissue and 2.08 kg of fat tissue. The day prior to AAU competition, an additional 2.73 kg were lost by dehydration to meet the 48.0-kg weight classification. Despite the subject's loss of lean and fat tissue, maximal aerobic power (approximately 67 ml X min-1 X kg-1) and muscular strength were maintained. These findings indicated that this wrestler was able to undergo a weight loss of approximately 8.0% and still maintain a high level of muscular strength and maximal aerobic power.
The present study was prompted by the controversy about the effect of heat-induced dehydration on human performance, and the popular Indian belief that it is not advisable to take water immediately after prolonged exertion in the sun. The points investigated were: (i) the effect of dehydration on some aspects of physical and mental performance, and (ii) variation in the post-dehydration performance caused by the timing of rehydration. Dehydration amounting to 2% of body weight did not impair mechanical efficiency while 3% dehydration reduced the endurance time for isometric contraction of extensors of the forearm. The maximum isometric tension and mental performance, measured by proof reading and a choice reaction time experiment, were not affected. The studies suggested that once dehydration had been produced, rehydration or its timing did not make any difference. Analysis of the results in terms of the sequence in which the experiments were done suggested the influence of psychological factors on the performance measured.
Article
With increased interest and participation in physical activity, particularly in activities that develop and maintain cardiorespiratory fitness and control body weight and fat, evaluation of physical fitness has become an important aspect of preventive and rehabilitative medicine. The term physical fitness has many meanings; cardiorespiratory fitness, body composition, muscular strength, endurance, and flexibility are considered the most important components when assessing the average adult. A close estimate of fitness enables the practitioner to make sound decisions concerning exercise prescription and health management. Energy expenditure in treadmill exercise, bicycle ergometry and in the step test are discussed. Information on the measurement of body composition is also presented.
Article
Athletes reduce bodyweight for several reasons: to compete in a lower weight class; to improve aesthetic appearance; or to increase physical performance. Rapid bodyweight reduction (dehydration in 12 to 96 hours), typically with fluid restriction and increased exercise, is used by athletes competing in weight-class events. Gradual bodyweight reduction (over >1 week) is usually achieved by cutting energy intake to 75 to 130 kJ/kg/day. An intake of 100 kJ/kg/day results in a weekly bodyweight loss of roughly 1kg. Aerobic endurance capacity decreases after rapid bodyweight reduction, but might increase after gradual bodyweight reduction. Maximal oxygen uptake (V̇O2max) measured as L/min is unchanged or decreased after bodyweight loss, but V̇O2max measured as ml/kg/min may increase after gradual bodyweight reduction. Anaerobic performance and muscle strength are typically decreased after rapid bodyweight reduction with or without 1 to 3 hours rehydration. When tested after 5 to 24 hours of rehydration, performance is maintained at euhydrated levels. A high carbohydrate diet during bodyweight loss may help in maintaining performance. Anaerobic performance is not affected and strength can increase after gradual bodyweight reduction. Reductions in plasma volume, muscle glycogen content and the buffer capacity of the blood explain decreased performance after rapid bodyweight reduction. During gradual bodyweight loss, slow glycogen resynthesis after training, loss of muscle protein and stress fractures (caused by endocrinological disorders) may affect performance. Athletes’ bodyweight goals should be individualised rather than by comparing with other athletes. If the time between weigh-in and competition is
This study investigated the effects of post-exercise rehydration with fluid alone or with a meal plus fluid. Eight healthy volunteers (five men, three women) were dehydrated by a mean of 2.1 (SEM 0.0)% of body mass by intermittent cycle exercise in a warm [34 (SEM 0) degrees C], humid [55 (SEM 1)% relative humidity] environment. Over 60 min beginning 30 min after exercise, the subjects ingested a commercially-available sports drink (21 mmol.l-1 Na+, 3.4 mmol.l-1 K+, 12 mmol.l-1 Cl-) on trials A and B: on trial C a standard meal [63 kJ.kg-1 body mass (53% CHO, 28% fat, 19% protein; 0.118 mmol.kJ-1 Na+, 0.061 mmol.kJ-1 K+)] plus drink (1 mmol.l-1 Na+, 0.4 mmol.l-1 K+, 1 mmol.l-1 Cl-) were consumed. Water intake (in millilitres) was 150% of the mass loss (in grams). The trials took place after an overnight fast and were separated by 7 days. Blood and urine samples were collected at intervals throughout the study. Blood was analysed for haematocrit, haemoglobin concentration, serum osmolality, Na+, K+ and Cl- concentrations and plasma angiotensin II concentration. Urine volume, osmolality and electrolyte concentrations were measured. Dehydration resulted in a mean 5.2 (SEM 1.3)% reduction in plasma volume. With the exception of serum osmolality, which was higher on trial B than A at the end of the rehydration period, no differences were recorded for any of the measured parameters between trials A and B. Cumulative urine output following rehydration was lower (P < 0.01) on trial C [median 665 (range 396-1190)ml] than on trial B [median 934 (range 550-1403)ml] which was not different (P = 0.44) from trial A [median 954 (range 474-1501)ml]. Less urine was produced over the 1-h period ending 2 h after rehydration on trial C than on B (P = 0.01). On trials A and B the subjects were in net negative fluid balance by 337 (range 779-minus 306) ml and 373 (range 680-minus 173)ml, respectively (P < 0.01): on trial C the subjects were no different from their initial euhydrated state [median minus 29 (range minus 421-137)ml] 6 h after the end of rehydration (P = 1.00). A larger fraction of total water intake was retained when the standard meal plus drink was consumed. This may have been due to the larger quantities of Na+ and K+ ingested with the meal [mean 63 (SEM 4) mmol Na+, 21.3 (SEM 1.3)mmol K+] than with the drink [mean 42(SEM 2)mmol Na+, 6.8 (SEM 0.4)mmol K+]. There was no difference between trials B and C in any of the measured blood parameters, but urinary Na+ and K+ excretion were both higher on trial C and B. These results suggest that post-exercise fluid replacement can be achieved by ingestion of water if consumed in sufficient volume together with a meal providing significant amounts of electrolytes.
Article
Collegiate wrestlers (N = 12) consumed a formula, hypoenergy diet (18 kcal.kg-1, 60% carbohydrate) without dehydration for 72 h. For the next 5 h, the athletes were fed either a 75% (HC) or a 47% (MC) carbohydrate formula diet of 21 kcal.kg-1. Each wrestler performed three anaerobic arm ergometer performance tests (TEST1, before weight loss; TEST2, after weight loss; TEST3, after refeeding). Blood withdrawn just before and after each test was analyzed for pH, bicarbonate, base excess, glucose, and lactate. Both groups had a similar significant reduction in total work done during TEST2 (92.4% of TEST1). Work done in TEST3 by HC was 99.1% of TEST1 while MC did 91.5% of their initial work (P = 0.1). Peak power was unaffected by the treatment. Plasma lactate significantly increased during the performance test from 1.72 to 21.91 mmol.l-1 as did plasma glucose from 4.88 to 5.25 mmol.l-1 when groups and trials were collapsed. Lactate accumulation was diminished during TEST2 compared with the other tests. Although the exercise bout reduced pH, bicarbonate, and base excess, there was no difference in the effect by group. In conclusion, weight loss by energy restriction significantly reduced anaerobic performance of wrestlers. Those on a high carbohydrate refeeding diet tended to recover their performance while those on a moderate carbohydrate diet did not. The changes in performance were not explained by the acid/base parameters measured.
Article
Overtraining is primarily related to sustained high load training, often coupled with other stressors. Studies in animal models have suggested that unremittingly heavy training (monotonous training) may increase the likelihood of developing overtraining syndrome. The purpose of this study was to extend our preliminary observations by relating the incidence of illnesses and minor injuries to various indices of training. We report observations of the relationship of banal illnesses (a frequently cited marker of overtraining syndrome) to training load and training monotony in experienced athletes (N = 25). Athletes recorded their training using a method that integrates the exercise session RPE and the duration of the training session. Illnesses were noted and correlated with indices of training load (rolling 6 wk average), monotony (daily mean/standard deviation), and strain (load x monotony). It was observed that a high percentage of illnesses could be accounted for when individual athletes exceeded individually identifiable training thresholds, mostly related to the strain of training. These suggest that simple methods of monitoring the characteristics of training may allow the athlete to achieve the goals of training while minimizing undesired training outcomes.