Hydration and Muscular Performance

The Autoregulation Rest-Redistribution Training Method Mitigates Sex Differences in Neuromuscular and Perceived Fatigue During Resistance Training

PURPOSE

To examine the sex differences in performance and perceived fatigue during resistance training prescribed using traditional (TRA) and autoregulation rest-redistribution training (ARRT) approaches.

METHODS

Twelve resistance-trained men and 12 women completed 2 sessions including the bench-press exercise matched for load (75% of 1-repetition maximum), volume (24 repetitions), and total rest (240 s). Sessions were performed in a counterbalanced randomized design with TRA consisting of 3 sets of 8 repetitions with 120-second interset rest and ARRT employing a personalized combination of clusters, repetitions per cluster, and between-clusters rest regulated with a 20% velocity-loss threshold. The effects of TRA and ARRT on velocity loss, unilateral isometric peak force, and rating of fatigue (ROF) were compared between sexes.

RESULTS

The velocity loss was generally lower during ARRT compared with TRA (-0.47% [0.11%]), with velocity loss being mitigated by ARRT to a greater extent among males compared with females (-0.37% [0.15%]). A smaller unilateral isometric peak force decline was observed after ARRT than TRA among males compared with females (-38.4 [8.4] N). Lower ROF after ARRT than TRA was found among males compared to females (-1.97 [0.55] AU). Additionally, males reported greater ROF than females across both conditions (1.92 [0.53] AU), and ARRT resulted in lower ROF than TRA overall (-0.83 [0.39] AU).

CONCLUSIONS

The ARRT approach resulted in decreased velocity loss, peak force impairment, and ROF compared with TRA in both sexes. However, male subjects exhibited more pronounced acute within-session benefits from the ARRT method.

Partial and Complete Fluid Replacement Maintains Exercise Performance in a Warm Environment Following Prolonged Cold-Water Immersion

ABSTRACT

Wheelock, CE, Stooks, J, Schwob, J, Hess, HW, Pryor, RR, and Hostler, D. Partial and complete fluid replacement maintains exercise performance in a warm environment following prolonged cold-water immersion. J Strength Cond Res 38(2): 290-296, 2024-Special warfare operators may be exposed to prolonged immersion before beginning a land-based mission. This immersion will result in substantial hypohydration because of diuresis. This study tested the hypothesis that both partial and full postimmersion rehydration would maintain performance during exercise in the heat. Seven men (23 ± 2 years; V̇o2max: 50.8 ± 5.3 ml·kg-1·min-1) completed a control trial (CON) without prior immersion and 3 immersion (18.0°C) trials without rehydration (NO) or with partial (HALF) or full (FULL) rehydration. After immersion, subjects completed a 60-minute weighted ruck march (20.4 kg; 5.6 kph) and a 15-minute intermittent exercise protocol (iEPT) in a warm environment (30.0°C and 50.0% relative humidity). The primary outcome was distance (km) covered during the iEPT. A priori statistical significance was set to p ≤ 0.05. Immersion resulted in 2.3 ± 0.4% loss of body mass in all immersion trials (p < 0.01). Distance covered during the first 13-minute interval run portion of iEPT was reduced in the NO rehydration trial (1.59 ± 0.18 km) compared with all other conditions (CON: 1.88 ± 0.18 km, p = 0.03; HALF: 1.80 ± 0.18 km, p < 0.01; FULL: 1.86 ± 0.28 km, p = 0.01). During the final 2 minutes of the iEPT, distance in the NO rehydration trial (0.31 ± 0.07 km) was reduced compared with the FULL rehydration trial (0.37 ± 0.07 km; p < 0.01) but not compared with CON (0.35 ± 0.07 km; p = 0.09) or HALF (0.35 ± 0.07 km; p = 0.08). Both partial and full postimmersion fluid replacement maintained intermittent exercise performance and should be applied as rehydration strategies.

Analysis of potential hydration opportunities during future football tournaments based on data from the 2018 FIFA World Cup

The World Cup is traditionally held oppressive thermal conditions. Therefore, teams should follow heat strain mitigation strategies, including optimal fluid ingestion. The objective of this analysis was to assess and visually communicate match-based World Cup player hydration opportunities and behaviors. Broadcast recordings of the 2018 World Cup (June-July) were analyzed. Descriptive data were reported for match duration, the number, type, and duration of breaks, and player-initiated hydration moments, as well as environmental conditions categorized as 'no thermal stress' and 'thermal heat stress.' The median number and interquartile range of total match breaks were 7 [5-8] during official breaks, with a duration of 42 [23-72] seconds. There were 2 [1-3] player-initiated hydration moments per game, with a duration of 77 [55-100] seconds. On top of the 29% (#126) of breaks in which drinking occurred, an additional 26% (#33) of self-initiated drinking was registered with a duration of 7 [4-28] seconds without an official break. There was no significant difference (P = 0.22) in self-initiated hydration between thermal conditions. Relative percentages showed suboptimal use of substitution (14%) and VAR (38%) breaks vs. injury breaks (75%). In conclusion, football players did not sufficiently use available breaks to hydrate.

Perceptions of the importance of sports nutrition knowledge and barriers in implementing them: a qualitative study among track and field stakeholders in Sri Lanka

BACKGROUND

Integrating the core aspects of sports nutrition knowledge [SNK] into the multidisciplinary team is critical to improving an athlete's performance and well-being. Conducting in-depth interviews with members of the sports-related team is a comprehensive method of gathering information on various aspects of SNK. This qualitative study aimed to examine the opinions and beliefs of stakeholders in athletics regarding the importance of SNK.

METHODS

Fifteen professional track and field athletes and stakeholders were recruited into the study. Separate in-depth interviews were conducted to collect information within four key themes. Practical difficulties in getting an appropriate meal were included in an additional theme. Thematic analysis was performed using NVIVO v10.0.

RESULTS

All participants were mindful of the importance of proper food habits for overall athletic outcomes and reported different opinions on meal timing and composition. The opinions on supplements were heterogeneous and both positive and negative claims were reported. Beliefs regarding hydration demonstrated that the cohort was well aware of the significance of adequate hydration plus the signs and consequences of dehydration with many reporting experiences of the negative consequences of dehydration. All respondents reported that both alcohol and smoking may have an adverse impact on performance and health.

CONCLUSIONS

All respondents emphasized the importance of proper food habits for sports performance and well-being, but also identified barriers to optimizing nutrition.

Isolate Whey Protein Promotes Fluid Balance and Endurance Capacity Better Than Isolate Casein and Carbohydrate-Electrolyte Solution in a Warm, Humid Environment

Protein ingestion is known to enhance post-exercise hydration. Whether the type of protein (i.e., whey, casein) can alter this response is unknown. Accordingly, this study aimed to compare the effects of the addition of milk-derived whey isolate or casein protein to carbohydrate-electrolyte (CE) drinks on post-exercise rehydration and endurance capacity. Thirty male soldiers (age: 24 ± 2.1 y; VO2max: 49.3 ± 4.7 mL/kg/min) were recruited. Upon losing ~2.2% of body mass by running in warm and humid conditions (32.3 °C, 76% relative humidity [RH]), participants ingested either a CE solution (66 g/L carbohydrate [CHO]), or CE plus isolate whey protein (CEW, 44 g/L CHO, 22 g/L isolate whey), or CE plus isolate casein protein (CEC, 44 g/L CHO, 22 g/L isolate casein) beverage in a volume equal to 150% of body mass loss. At the end of the 3 h rehydration period, a positive fluid balance was higher with CEW (0.22 L) compared to CEC (0.19 L) and CE (0.12 L). Overall mean fluid retention was higher in CEW (80.35%) compared with the CE (76.67%) and CEC trials (78.65%). The time of the endurance capacity test [Cooper 2.4 km (1.5 miles) run test] was significantly higher in CEC (14.25 ± 1.58 min) and CE [(12.90 ± 1.01 min; (p = 0.035)] than in CEW [(11.40 ± 1.41 min); (p = 0.001)]. The findings of this study indicate that the inclusion of isolate whey protein in a CE solution yields superior outcomes in terms of rehydration and enhanced endurance capacity, as compared to consuming the CE solution alone or in conjunction with isolate casein protein.

Prediction of body water compartments by raw bioelectrical impedance parameters in athletes: Comparison between series and parallel measurements

BACKGROUND

The aim of this study was to determine the predictive role of series and parallel bioelectrical impedance-derived parameters in predicting total body (TBW), intracellular (ICW), and extracellular water (ECW) in athletes.

METHODS

This cross-sectional study analyzed 134 male (21.33 ± 5.11 years) and 64 female (20.45 ± 5.46 years) athletes. Using dilution techniques, TBW and ECW were determined while ICW was the difference between both. Raw and standardized for height (/H) bioelectrical resistance (R), reactance (Xc), and impedance (Z) values were obtained using a phase-sensitive device at a single frequency in a series array (s). These were mathematically transformed in a parallel array (p) and capacitance (CAP). Fat-free mass (FFM) was assessed by dual-energy X-ray absorptiometry.

RESULTS

Multiple regressions adjusted for age and FFM show that R/Hs, Z/Hs, R/Hp, and Z/Hp were significant predictors of TBW (p < 0.001 in females and males). While Xc/Hs did not predict ICW, Xc/Hp was a predictor (p < 0.001 in females and Males). In females, R/H and Z/H predicted similarly TBW, ICW, and ECW. In males, R/Hs was considered a better predictor than R/Hp for TBW and ICW, and the Xc/Hp was considered the best predictor for ICW. Another significant predictor of ICW was CAP (p < 0.001 in females and males).

CONCLUSION

This study highlights the potential value of parallel bioelectrical impedance values to identify fluid compartments in athletes as an alternative to the regularly used series measurements. Moreover, this study supports Xc in parallel, and ultimately CAP, as valid indicators of cell volume.

Carbohydrate or Electrolyte Rehydration Recovers Plasma Volume but Not Post-immersion Performance Compared to Water After Immersion Diuresis

INTRODUCTION

We tested the hypothesis that a carbohydrate (CHO: 6.5%) or carbohydrate-electrolyte (CHO + E: 6.5% + 50 mmol/L NaCl) drink would better recover plasma volume (PV) and exercise performance compared to water (H2O) after immersion diuresis.

METHODS

Twelve men (24 ± 2 years; 82.4 ± 15.5 kg; and V̇O2max: 49.8 ± 5.1 mL · kg-1 · min-1) completed four experimental visits: a no-immersion control (CON) and three 4-h cold-water (18.0 °C) immersion trials (H2O, CHO, and CHO + E) followed by exercise in a warm environment (30 °C, 50% relative humidity). The exercise was a 60-minute loaded march (20.4 kg; 55% VO2max) followed by a 10-minute intermittent running protocol. After immersion, subjects were rehydrated with 100% of body mass loss from immersion diuresis during the ruck march. PV is reported as a percent change after immersion, after the ruck march, and after the intermittent running protocol. The intermittent running protocol distance provided an index of exercise performance. Data are reported as mean ± SD.

RESULTS

After immersion, body mass loss was 2.3 ± 0.7%, 2.3 ± 0.5%, and 2.3 ± 0.6% for H2O, CHO, and CHO + E. PV loss after immersion was 19.8 ± 8.5% in H2O, 18.2 ± 7.0% in CHO, and 13.9 ± 9.3% in CHO + E, which was reduced after the ruck march to 14.7 ± 4.7% (P = .13) in H2O, 8.8 ± 8.3% (P < .01) in CHO, and 4.4 ± 10.9% (P = .02) in CHO + E. The intermittent running protocol distance was 1.4 ± 0.1 km in CON, 1.4 ± 0.2 km in H2O, 1.4 ± 0.1 km in CHO, and 1.4 ± 0.2 km in CHO + E (P = .28).

CONCLUSIONS

Although CHO and CHO + E better restored PV after immersion, post-immersion exercise performance was not augmented compared to H2O, highlighting that fluid replacement following immersion diuresis should focus on restoring volume lost rather than fluid constituents.

Prompted hands-free drinking improves simulated race car driving in a hot environment

Race car drivers are often hypohydrated during a race. The FluidLogic drink system is a hands-free, prompted drinking system that is hypothesized to increase the likeliness of drivers' consuming fluids and thereby mitigating hypohydration. To test the hypothesis, 20 elite professional race car drivers participated in a 2-day cross-over study in which they drove on a race simulator in an environmental chamber that was heated to regulation cockpit temperature (38°C). Drivers used either the FluidLogic drink system or a standard in-car water bottle system (Control) on one of each testing day. The results indicated that there was consistent fluid consumption with the FluidLogic system, while the Control condition elicited fluid consumption in bolus doses. The Control condition was associated with moderate (0.5%) increased core body temperature (P < 0.05) and substantial (3.3%) increased urine-specific gravity (P < 0.001) as compared to the FluidLogic condition. Driving performance metrics indicated that lap times during the Control Condition were 5.1 ± 1.4 (4.1%) seconds slower (P < 0.05) than the FluidLogic Condition, due to driving errors that occurred in the high-speed corners. Based on these results, prompted hands-free drinking can mitigate hypohydration and performance loss in automobile racing drivers.

Effects of Different Rapid Weight Loss Strategies and Percentages on Performance-Related Parameters in Combat Sports: An Updated Systematic Review

Most combat sports (CS) are structured in weight categories, and it is very common to carry out body weight adjustment strategies in order to compete in lower weight categories. For this reason, different rapid weight loss (RWL) strategies are usually performed to pass the pre-competition weigh-in test, and then a replenishment of fluids and carbohydrate-rich foods is conducted in an attempt to recover the weight and avoid a performance loss. In this context, no clear references have been found on whether these types of strategies have negative effects, impairing the athlete's combat and/or physical performance. For this reason, the aim of this study was to review the scientific literature on the effect of rapid weight reduction strategies on the performance of CS athletes. A literature search was performed through four different databases (PubMed, SPORTDiscus, Web of Science and ScienceDirect). Four inclusion criteria were established as follows: (1) the subjects had to be competitors in the CS and carry out RWL strategies; (2) at least two measurement points, that is, normal conditions and dehydration condition; (3) measurements in a real competition or simulating the same conditions; (4) original research articles written in English or Spanish and available in full text. Finally, a total of 16 articles were finally included in this research. All subjects (n = 184) were athletes from combat disciplines, with a minimum of 3-4 years of practice, as well as with certain experience in RWL. Six of the studies reported that an RWL strategy of around 5% of body weight loss did not affect performance parameters. However, the other ten studies with RWL between 3 and 6% or even higher reported negative effects or impairments on different parameters related to performance and/or athlete's psychophysiology, such as perceived fatigue, mood states, strength and power production, as well as changes in hormonal, blood and urine parameters, body composition, or the kinematics of the technical gesture. Although there is still no clear answer to the issue approached in this research, in general terms, it seems that in order to guarantee an acceptable athletic performance of the competitor, the weight loss should not exceed 3% to ≤5% of body weight together with ≥24 h for adequate (or at least partial) recovery and rehydration processes. In addition, it is highly recommended to lose weight progressively over several weeks, especially focusing on competitions lasting several days, as well as multiple rounds or qualifying stages.

Comparison between digital and paper urine color to assess hydration status

PURPOSE

The purpose of this study was to investigate associations between digital urine color and paper urine color with other urine indices to assess hydration status.

METHODS

Twelve male subjects (mean ± standard deviation; age, 26 ± 8 years; body mass, 57.8 ± 5.3 kg; height, 177.5 ± 8.9 cm; VO_2max, 57.8 ± 5.8 ml·kg^-1·min^-1) performed four exercise trials in the heat. Before and following exercise trials, subjects provide urine samples. Urine samples were measured using a digital urine color chart on a portable device screen. Urine samples were also assessed with urine specific gravity (USG), urine osmolality (UOsmo), and a validated paper urine color chart.

RESULTS

There were extremely large associations found between digital urine color and paper urine color (r = 0.926, p < 0.001). Correlation coefficients showing associations with USG and UOsmo were similar between digital urine color (USG, r = 0.695, p < 0.001; UOsmo, r = 0.555, p < 0.001) and paper urine color (USG, r = 0.713, p < 0.001; UOsmo, r = 0.570, p < 0.001). Bland-Altman analysis indicated that no proportional bias was observed between digital and paper urine colors (bias, - 0.148; SD of bias, 0.492; 95% LOA, - 1.11, 0.817; p = 0.094).

CONCLUSIONS

Strong associations were found between digital and paper urine colors with no proportional bias. Furthermore, the degree of associations with USG and UOsmo was similar between digital and paper urine color. These results indicate that digital urine color is a useful tool to assess hydration status and this method could be used as an alternative method to using paper urine color.

Personalizing Resistance Training Mitigates Neuromuscular and Perceived Fatigue: The Autoregulation Cluster Training Method

PURPOSE

To compare predetermined and autoregulated resistance training sessions on velocity loss and perceived fatigue.

METHODS

Twenty-six resistance-trained men completed 3 sessions including the back-squat and bench-press exercises matched for load (75% of 1-repetition maximum), volume (24 repetitions), and total rest (240 s). Sessions were randomly performed as traditional set (TRA), 3 sets of 8 repetitions with 120-second interset rests; cluster interset-rest redistribution (IRR), 6 clusters of 4 repetitions with 48-second between-clusters rests; and autoregulation cluster training (ACT), a personalized combination of clusters, repetitions per cluster, and between-clusters rest regulated on a velocity loss threshold. The comparative effects were evaluated on velocity loss outputs measured with a linear encoder and perceived fatigue responses reported using a single-item scale.

RESULTS

IRR and ACT induced less velocity loss than TRA (b = -2.09, P < .001). ACT also mitigated velocity loss more than IRR (b = -2.31, P < .001). The back squat resulted in greater velocity loss compared to the bench press (b = 1.83, P < .001). Perceived fatigue responses mirrored the pattern observed for the velocity loss outputs (IRR and ACT vs TRA: b = -0.64, P < .001; ACT vs IRR: b = -1.05, P < .001; back squat vs bench press: b = 0.46, P = .005).

CONCLUSIONS

IRR and ACT reduced neuromuscular and perceived fatigue, likely due to their cluster-set structures' embedding frequent windows of interset rest. However, the ACT was overall more effective, presumably given its personalized structure.

Exercise-related hemoconcentration and hemodilution in hydrated and dehydrated athletes: An observational study of the Hungarian canoeists

Hemoconcentration during exercise is a well-known phenomenon, however, the extent to which dehydration is involved is unclear. In our study, the effect of dehydration on exercise-induced hemoconcentration was examined in 12 elite Hungarian kayak-canoe athletes. The changes of blood markers were examined during acute maximal workload in hydrated and dehydrated states. Dehydration was achieved by exercise, during a 120-minute extensive-aerobic preload. Our research is one of the first studies in which the changes in blood components were examined with a higher time resolution and a wider range of the measured parameters. Hydration status had no effect on the dynamics of hemoconcentration during both the hydrated (HS) and dehydrated (DHS) load, although lower maximal power output were measured after the 120-minute preload [HS Hemoglobin(Hgb)Max median 17.4 (q1 17.03; q3 17.9) g/dl vs. DHS HgbMax median 16.9 (q1 16.43; q3 17.6) g/dl (n.s); HS Hematocrit(Hct)Max 53.50 (q1 52.28; q3 54.8) % vs. DHS HctMax 51.90 (q1 50.35; q3 53.93) % (n.s)]. Thirty minutes after the maximal loading, complete hemodilution was confirmed in both exercises. Dehydration had no effect on hemoconcentration or hemodilution in the recovery period [HS HgbR30' 15.7 (q1 15.15; q3 16.05) g/dl (n.s.) vs. DHS HgbR30' 15.75 (q1 15.48; q3 16.13) g/dl (n.s.), HS HctR30' 48.15 (q1 46.5; q3 49.2) % vs. DHS HctR30' 48.25 (q1 47.48; q3 49.45) % (n.s.)], however, plasma osmolality did not follow a corresponding decrease in hemoglobin and hematocrit in the dehydrated group. Based on our data, metabolic products (glucose, lactate, sodium, potassium, chloride, bicarbonate ion, blood urea nitrogen) induced osmolality may not play a major role in the regulation of hemoconcentration and post-exercise hemodilution. From our results, we can conclude that hemoconcentration depends mainly on the intensity of the exercise.

Effects of Elevated Body Temperature on Selected Physiological Indices and Thermal Stress in Athletes and Non-Athletes

The purpose of this study was to determine the effects of active and passive overheating. A group of athletes (A) and non-athletic men (N) underwent an exercise stress test at elevated ambient temperature and sauna bathing until an increase in rectal temperature of 1.2°C was observed. It was shown that group A performed physical exercise for a longer period of time, which elicited significantly higher amounts of work performed in the stress test. Both forms of overheating caused a significant decrease in BM and a significant change in plasma volume, while greater dehydration was observed after active overheating. Changes observed in group A were higher than in group N. MCV levels were initially higher in group A. The levels in both groups decreased after sauna bathing, although in non-athletes the decrease was greater. Both forms of overheating increased Hb, HCT, and SBP, while only the non-athletic group showed a decrease in DBP after the exercise stress test. However, a decrease in DBP was observed in both groups after sauna bathing. The PSI increased after both tests, yet to a higher extent after the stress test than after sauna bathing. The PSI was negatively correlated with VO2max in both groups. The increase in cortisol concentration was higher after sauna bathing. There was a correlation between cortisol levels and the work performed during the stress test in group A. Endurance training resulted in more efficient thermoregulatory mechanisms in athletes.

A questionnaire study on the knowledge, attitudes, and practices of fluid replacement and urination among Chinese elite athletes

OBJECTIVE

To evaluate the knowledge, attitudes and practices (KAP) of Chinese elite athletes about fluid replacement and urination.

METHODS

A cross-section study was carried out among Chinese national and national youth teams from March to April 2020, using a pretested questionnaire. The 42-questions questionnaire was designed to assess the KAP regarding fluid replacement and urination. The questionnaire included knowledge of fluid replacement (KFR), attitudes of fluid replacement (AFR), knowledge of urination (KU), and attitudes of urination (AU), which were awarded 20 scoring points. Descriptive statistics, independent samples t-tests, one-way ANOVA, Pearson's correlation analysis, Multiple linear stepwise regression and Chi-square test were performed.

RESULTS

A total of 779 valid questionnaires were collected and the effective rate is 98.4%. We finally conducted an assessment of 646 questionnaires of elite athletes. The mean score for KFR, AFR, KU, and AU was 2.8±1.3, 2.3±0.6, 3.0±1.5, and 2.1±0.8, respectively, with higher scores indicating positive hydration knowledge and attitudes. KFR and AFR scores of winter sports athletes were higher than those of summer sports athletes(P<0.05). Athletes who had lower athletic grades and training years had a worse KFR(P<0.05). Only 31.0% athletes knew that rehydration should be carried out before, during, and after training, which was scarcer among women, lower-athletic grades athletes, or athletes with lower training years (P<0.05). Male athletes had a worse KU but a better AU than female athletes(P<0.05). And athletes who were international-class athletic grades had the highest KU scores(P<0.05). The athletic grades and sport events were the main factors influencing the total scores of knowledge and attitudes (P<0.05, 95% CI -0.789--0.168,95% CI 0.025-1.040). Most of athletes tend to get hydration knowledge from internet. In practices, thirst is the main reason for rehydration (77.9%). The percentages of athletes with normal urine color (42.0%), frequency (75.0%,) and volume (20.0%) were low.

CONCLUSIONS

These findings indicate that Chinese elite athletes did not have sufficient KAP on fluid replacement and urination, more marked in the individuals who were summer sport events, the lower athletic grades and in lower training years. It is recommended that education should be provided in the early stages of professional training for athletes.

Countermovement jump, handgrip, and balance performance change during euhydration, mild-dehydration, rehydration, and ad libitum drinking

Objective

To examine the effects of euhydration, mild-dehydration, rehydration, and ad libitum drinking on countermovement jump (CMJ), handgrip strength, and performance of balance error scoring system test (BESS).

Methods

Eighteen healthy male subjects (mean[M]±standard deviation[SD]; age, 23±3y; body mass, 80.1 ± 9.7 kg; height, 175.8 ± 5.7 cm) participated in this study. Participants reported to the laboratory to perform CMJ, handgrip strength, and BESS with different hydration statuses (euhydrated, EUH; when they initially sensed thirst, THIRST; dehydrated, DEH; following 30 minutes of rehydration, REH; and following 24-h ad libitum drinking, AD).

Results

CMJ at EUH (M±SD; 54.6 ± 3.0 cm) was significantly higher than DEH (52.8 ± 3.0 cm, p = 0.027) and REH (52.6 ± 2.8 cm, p < 0.001). However, there was no difference between DEH and REH (p = 0.643). CMJ at THIRST (54.9 ± 3.0 cm, p = 0.004) was higher than REH. Also, AD (53.8 ± 2.8 cm, p = 0.027) was higher than REH. In left handgrip strength, THIRST (48.6 ± 9.5 kg) was higher than EUH (46.7 ± 10.1 kg, p = 0.018), DEH (45.8 ± 10.0 kg, p = 0.013), REH (46.1 ± 9.5 kg, p = 0.004), and AD (47.1 ± 9.7 kg, p = 0.05). Additionally, in the single-leg stance on a foam pad, more BESS errors were found at THIRST (6 ± 2) compared to EUH (5 ± 2, p = 0.007) and AD (5 ± 2, p = 0.002).

Conclusion

The findings of this study were: ∼2% of mild dehydration induced by 24-h fluid restriction decreased lower body power measured by CMJ, acute rehydration did not restore the loss of lower body power induced by dehydration, and ∼0.5–0.9% of dehydration did not decrease lower body power.

Computational Study of the Impact of Dehydration-Induced Vocal Fold Stiffness Changes on Voice Production

OBJECTIVE

Systemic vocal fold dehydration is known to increase vocal fold stiffness, which has been hypothesized to have important effect on voice production. However, it remains unclear whether the dehydration-induced vocal fold stiffness changes can have a noticeable impact on phonation, particularly in normal phonation conditions. The goal of this study was to investigate the impact of vocal fold stiffness changes due to vocal fold systemic dehydration and its significance in daily communication.

METHODS

Parametric computational simulation using a three-dimensional vocal fold model, in which the vocal fold stiffness was varied as a function of systemic dehydration levels based on previously-reported experimental data.

RESULTS

The results showed that systemic dehydration had significant effects on voice production only at high levels of dehydration, at which dehydration increased the phonation threshold pressure and fundamental frequency, and decreased glottal opening area, vocal intensity and glottal efficiency. The effect depended mainly on the overall dehydration level but was also slightly affected by the dehydration distribution and muscular control. However, for dehydration levels typical of normal phonation conditions, the effect was negligible.

CONCLUSIONS

The results indicated that dehydration-induced vocal fold stiffness change likely is not an important mechanism through which vocal fold systemic dehydration affects voice production. Nevertheless, a large decrease in glottal efficiency implies a possible perceived increase of vocal effort under a realistic dehydration condition.

The Influence of a Competitive Field Hockey Match on Cognitive Function

Despite the known positive effects of acute exercise on cognition, the effects of a competitive team sport match are unknown. In a randomized crossover design, 20 female and 17 male field hockey players (19.7 ± 1.2 years) completed a battery of cognitive tests (Visual Search, Stroop, Corsi Blocks, and Rapid Visual Information Processing) prior to, at half-time, and immediately following a competitive match (or control trial of seated rest); with effect sizes (ES) presented as raw ES from mixed effect models. Blood samples were collected prior to and following the match and control trial, and analyzed for adrenaline, noradrenaline, brain derived neurotrophic factor (BDNF), cathepsin B, and cortisol. The match improved response times for a simple perception task at full-time (ES = –14 ms; P < 0.01) and response times on the complex executive function task improved at half-time (ES = –44 ms; P < 0.01). Working memory declined at full-time on the match (ES = –0.6 blocks; P < 0.01). The change in working memory was negatively correlated with increases in cortisol (r = –0.314, P = 0.01; medium), as was the change in simple perception response time and the change in noradrenaline concentration (r = –0.284, P = 0.01; small to medium). This study is the first to highlight the effects a competitive hockey match can have on cognition. These findings have implications for performance optimization, as understanding the influence on specific cognitive domains across a match allows for the investigation into strategies to improve these aspects.

Bioelectrical Impedance Vector and Creatine Phosphokinase Changes Induced by a High-Intensity Training Session in Rink Hockey Players

This study aimed to analyze anthropometric and whole-body/muscle-localized bioelectrical impedance vector analysis (BIVA) adaptations and their relation to creatine kinase (CK) as a biomarker of muscle damage in a group of seven male players in the maximum category of professional rink hockey. There were three checkpoint assessments in relation to a high-intensity training session: pre-session (PRE), post-session (POST), and 24 h-post-session (POST24H). The resistance, reactance, and impedance module were adjusted by height (R/h, Xc/h, and Z/h, respectively). The Wilcoxon signed-rank test was used to compare the data at baseline and follow-up, while Spearman correlation was used to explore the relationship between CK and the rest of the parameters. The results registered a decrease in body mass at POST (p = 0.03) and a reestablishment at POST24H (p = 0.02). Whole-body BIVA registered a significant increase in R/h between PRE–to–POST (p = 0.02) and returned to baseline values at POST24H (p = 0.02), which was expected since this parameter is related to hydration processes. Muscle-localized BIVA in the rectus femoris muscle showed an increase in both Xc/h and phase angle in POST (p = 0.04 and p = 0.03, respectively) and a decrease in Xc/h at POST24H (p = 0.02). CK correlated with R/h in the rectus femoris at all the checkpoints (PRE–to–POST: r = 0.75, p = 0.05; PRE–to–POST24H: r = 0.81, p = 0.03; POST–to–POST24H: r = 0.82, p = 0.02). Our results indicate that BIVA is a sensitive methodology to assess general and muscle-localized hydration induced by a high-intensity training session in rink hockey players. A correlation between BIVA and CK was also reported.

Effects of Mental Training Through Imagery on the Competitive Anxiety of Adolescent Tennis Players Fasting During Ramadan: A Randomized, Controlled Experimental Study

This study aimed to analyze the effects of mental training through imagery on the competitive anxiety of adolescent tennis players fasting during Ramadan. This is an experimental study conducted with 38 male tennis players, randomly allocated to two groups: an experimental group (EG, n = 18), aged 16.9 ± 0.6 years, and a control group (CG, n = 20), aged 16.7 ± 0.8 years. The study was designed as a randomized, controlled experimental trial (registration code PACTR 202006847771700). CG watched historical videos of the Olympics, while EG performed mental training. The competitive anxiety state assessment was recorded four times. The first measurement was carried out 1 week before Ramadan, the second measurement during the first week of the month, the third measurement at the end of the second week, and, finally, the fourth measurement during the fourth week of Ramadan. Our results revealed a significant interaction (time × groups) for all competitive anxiety subscales. Higher intensity and direction scores for the cognitive and somatic anxiety subscales during Ramadan compared with before Ramadan for both groups could be reported at P < 0.001. Higher intensity and direction scores for the cognitive and somatic anxiety subscales during Ramadan compared with pre-Ramadan for both groups could be found at P < 0.01. This increase in scores was greater for the CG than for the EG in the middle and at the end of Ramadan at P < 0.001. Finally, for the self-confidence subscale score, results revealed that intensity and direction scores were lower during Ramadan compared with pre-Ramadan for the two groups at P < 0.01. The score for the intensity of self-confidence was higher for the EG compared with the CG at the end of Ramadan at P < 0.001. It was concluded that mental imagery training was effective in reducing anxiety (cognitive and somatic) and increasing self-confidence in the intensity dimension of adolescent tennis players who fast during Ramadan.

Weight-Cutting Implications for Competition Outcomes in Mixed Martial Arts Cage Fighting

ABSTRACT

Brechney, GC, Chia, E, and Moreland, AT. Weight-cutting implications for competition outcomes in mixed martial arts cage fighting. J Strength Cond Res 35(12): 3420-3424, 2021-Weight cutting is common among amateur and professional mixed martial arts (MMA) competitors because of the belief that it provides an advantage in combat sports. This study aimed to identify whether fight outcome (win vs. loss vs. type of loss) was influenced by magnitudes of body mass (BM) lost through weight cutting and BM regained before the fight after official weigh-in in amateur and professional MMA athletes with previous weight-cutting experience. Body mass data were collected using self-report from 75 MMA athletes (59 amateur and 16 professional) before commencing weight-cutting practices 7 days before weigh-in, by the regulating body at their official weigh-in 24 hours before the fight and through direct measurement immediately before competition. Data were analyzed according to win; loss by technical knockout or knockout (KO); loss by submission; or loss by the judge's decision. Athletes who lost their fight cut significantly more BM (10.6%) compared with athletes who won (8.6%) (p = 0.04, d = 0.48, 95% confidence interval [CI] = 0.02-0.93), but there were no differences between types of loss. There were no significant differences in recovered BM between athletes who won (6.8%) vs. lost (7.4%), or type of loss. Furthermore, there was a significant relationship between greater magnitudes of BM cut and greater likelihood of losing the fight (B = -0.12, P = 0.048), odd ratio 0.89 (95% CI: 0.79-1.00). This study provides the first line of evidence that excessive weight cutting may be detrimental to fight outcome in MMA.

Nutritional approaches to counter performance constraints in high-level sports competition

New Findings

What is the topic of this review?

The nutritional strategies that athletes use during competition events to optimize performance and the reasons they use them.

What advances does it highlight?

A range of nutritional strategies can be used by competitive athletes, alone or in combination, to address various event‐specific factors that constrain event performance. Evidence for such practices is constantly evolving but must be combined with understanding of the complexities of real‐life sport for optimal implementation.

Abstract

High‐performance athletes share a common goal despite the unique nature of their sport: to pace or manage their performance to achieve the highest sustainable outputs over the duration of the event. Periodic or sustained decline in the optimal performance of event tasks, involves an interplay between central and peripheral phenomena that can often be reduced or delayed in onset by nutritional strategies. Contemporary nutrition practices undertaken before, during or between events include strategies to ensure the availability of limited muscle fuel stores. This includes creatine supplementation to increase muscle phosphocreatine content and consideration of the type, amount and timing of dietary carbohydrate intake to optimize muscle and liver glycogen stores or to provide additional exogenous substrate. Although there is interest in ketogenic low‐carbohydrate high‐fat diets and exogenous ketone supplements to provide alternative fuels to spare muscle carbohydrate use, present evidence suggests a limited utility of these strategies. Mouth sensing of a range of food tastants (e.g., carbohydrate, quinine, menthol, caffeine, fluid, acetic acid) may provide a central nervous system derived boost to sports performance. Finally, despite decades of research on hypohydration and exercise capacity, there is still contention around their effect on sports performance and the best guidance around hydration for sporting events. A unifying model proposes that some scenarios require personalized fluid plans while others might be managed by an ad hoc approach (ad libitum or thirst‐driven drinking) to fluid intake.

Evaluation of the Body Composition and Selected Physiological Variables of the Skin Surface Depending on Technical and Tactical Skills of Kickboxing Athletes in K1 Style

BACKGROUND

Kickboxing is a combat sport with high demands on fitness and coordination skills. Scientific research shows that kickboxing fights induce substantial physiological stress. Therefore, it is important to determine the body composition of athletes before competitions and to analyze the skin temperature and skin pH during the fight.

METHODS

This study aimed to determine the body composition, skin temperature, and skin pH in kickboxers during a fight according to K1 rules. A total of 24 kickboxers (age range: 19 to 28 years) competing in a local K1 kickboxing league participated in the present study.

RESULTS

Changes in skin temperature and pH were observed and significant correlations were found between body composition and weight category.

CONCLUSIONS

Changes in skin temperature and pH were demonstrated after each round of the bout. Level of body fat and muscle tissue significantly correlates with technical-tactical skills of the K1 athletes studied.

Dehydration and Rapid Weight Gain Between Weigh-in and Competition in Judo Athletes: The Differences between Women and Men

This study aimed to investigate the sex differences in short-term weight change and hydration status in judo athletes. Thirty-five men and 15 women judo athletes voluntarily participated in this descriptive and repeated measures design study. Body mass, urine-specific gravity (USG), and body composition of the athletes were measured at the official weigh-in and the competition day's morning. Body mass of the athletes increased during recovery time between official weigh-in and before the competition (time factor; F_1-48 = 71.81, p < 0.001), this increase was higher in men athletes compared to women athletes (time-sex interaction; F_1-48 = 6.56, p = 0.01). With RWG, USG values of the women and men athletes decreased (time factor; F_1-48 = 8.53, p = 0.005). However, most of the athletes were still in significant or serious dehydration state. Unchanged values of total body water rates (TBW) supported dehydration in athletes before the competition (time factor, F_1-48 = 2.9, p = 0.091; time-sex interaction; F_1-48= 2.4, p = 0.122). The findings of the study indicated that RWG was higher in men athletes compared to women athletes, but hydration status was not affected by sex factor.Notwithstanding 15 hours of recovery between official weigh-in and the start of the competition, judo athletes were still in dehydrated state despite remaining within the limit set for RWG.

A quasi-experimental examination of weight-reducing dehydration practices in collegiate male rowers

Background

Lightweight rowers commonly utilize weight loss techniques over 24-h before competition to achieve the qualifying weight for racing. The objective was to investigate, using a quasi-experimental design, whether changes in weight resulting from dehydration practices are related to changes in proxies of bodily systems involved in rowing and whether these relationships depend on the dehydration technique used.

Methods

Twelve elite male rowers performed a power test, an incremental VO₂max test, and a visuomotor battery following: weight loss via thermal exposure, weight loss via fluid abstinence and then thermal exposure, and no weight loss. The total percent body mass change (%BMC), %BMC attributable to thermal exposure, and %BMC attributable to fluid abstinence were used to predict performance variables.

Results

Fluid abstinence but not thermal exposure was related to a lower total wattage produced on a incremental VO₂max test (b = 4261.51 W/1%BMC, 95%CI = 1502.68–7020.34), lower wattages required to elicit 2 mmol/L (b = 27.84 W/1%BMC, 95%CI = 14.69–40.99) and 4 mmol/L blood lactate (b = 20.45 W/1%BMC, 95%CI = 8.91–31.99), and slower movement time on a visuomotor task (b = -38.06 ms/1%BMC, 95%CI = -62.09–-14.03).

Conclusions

Dehydration related weight changes are associated with reductions in some proxies of bodily systems involved in rowing but depend on the dehydration technique used.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13102-021-00344-7.

Relationships Between WUT (Body Weight, Urine Color, and Thirst Level) Criteria and Urine Indices of Hydration Status

BACKGROUND

A Venn diagram consisting of percentage body mass loss, urine color, and thirst perception (weight, urine, thirst [WUT]) has been suggested as a practical method to assess hydration status. However, no study to date has examined relationships between WUT and urine hydration indices. Thus, the purpose of this study was to investigate relationships between urine specific gravity, urine osmolality, and the WUT criteria.

HYPOTHESIS

Urine specific gravity and urine osmolality indicate hypohydration when the WUT criteria demonstrate hypohydration (≥2 markers).

STUDY DESIGN

Laboratory cohort study.

LEVEL OF EVIDENCE

Level 3.

METHODS

A total of 22 women (mean ± SD; age, 20 ± 1 years; mass, 65.4 ± 12.6 kg) and 21 men (age, 21 ± 1 years; body mass, 78.7 ± 14.6 kg) participated in this study. First morning body mass, urine color, urine specific gravity, urine osmolality, and thirst level were collected for 10 consecutive days in a free-living situation. Body mass loss >1%, urine color >5, and thirst level ≥5 were used as the dehydration thresholds. The number of markers that indicated dehydration levels were counted and categorized into either 3, 2, 1, or 0 WUT markers that indicated dehydration. One-way analysis of variance with Tukey pairwise comparisons was used to assess the differences in urine specific gravity and urine osmolality between the different number of WUT markers.

RESULTS

Urine specific gravity in 3 WUT markers (mean ± SD [effect size], 1.021 ± 0.007 [0.57]; P = 0.025) and 2 WUT markers (1.019 ± 0.010 [0.31]; P = 0.026) was significantly higher than 1 WUT marker (1.016 ± 0.009). Urine mosmolality in 2 WUT markers (705 ± 253 mOsmol [0.43]; P = 0.018) was significantly higher than 1 WUT (597 ± 253 mOsmol). Meeting at least 2 WUT markers resulted in sensitivities of 0.652 (2 WUT criteria met) and 0.933 (3 WUT criteria met) to detect urine osmolality >700 mOsmol.

CONCLUSION

These results suggest that when 3 WUT markers are met, urine specific gravity and urine osmolality were greater than euhydration cutoff points. The WUT criterion is a useful tool to use in field settings to assess hydration status when first morning urine sample was used.

CLINICAL RELEVANCE

Athletes, coaches, sports scientists, and medical professionals can use WUT criteria to monitor dehydration with reduced cost and time.

Nutritional Risks among Adolescent Athletes with Disordered Eating

In their attempt to achieve the optimum weight or body shape for their activity, athletes frequently use harmful weight-control practices that may lead to the development of disordered eating or eating disorders. These practices are linked to several medical and mental consequences that may be more serious in adolescent athletes, as their bodies must meet both intensive growth demands and training requirements at the same time. Among other consequences, adolescent athletes may be at nutritional risk, due to their high nutrient needs and unhealthy eating behaviors. A literature review was conducted to examine the main nutritional risks and malnutrition issues faced by adolescent athletes that present disordered eating attitudes or eating disorders. Most studies refer to adult elite athletes, however research on adolescent athletes also indicates that the most common nutritional risks that may arise due to disordered eating include energy, macronutrient and micronutrient deficiencies, dehydration and electrolyte imbalances and changes in body composition that may lead to menstrual abnormalities, and decreased bone mass density. Educational programs and early detection of disordered eating and eating disorders are crucial to avoid the emergence and ensure timely management of nutrition-related problems in the vulnerable group of adolescent athletes.

Hydration to Maximize Performance and Recovery: Knowledge, Attitudes, and Behaviors Among Collegiate Track and Field Throwers

Hydration plays an important role in performance, injury prevention, and recovery for athletes engaged in competitive sports. Therefore, it is important that strength and conditioning coaches understand an athlete’s hydration needs to prevent illness and enhance performance. The purpose of this study was to identify hydration knowledge, attitudes, and behaviors of collegiate track and field throwers, as well as identify barriers to hydration and sources of nutritional information. The Rehydration and Refueling in Collegiate Track and Field Throwers Survey was sent to 271 track and field thrower coaches with a request to forward the email to current track and field throwers. Pearson correlation coefficients were calculated regarding knowledge, attitude, and behavior scores among the participants in this sample. Differences among response patterns were assessed via Chi-square analysis. Alpha level was set at p = .05. Results demonstrated that 97.3% (n = 287) of respondents knew that dehydration would decrease performance, but 50.5% (n = 149) erroneously believed thirst was the best indicator of dehydration. Chi-square analysis demonstrated a significant difference in reported values between participants who intended to eat a performance-enhancing diet and those who consumed less fluid than recomended values (207 – 295 m)l in the 2-3 hours prior to competition (χ2 = 10.87, p < .05). Pearson correlation coefficients demonstrated a large association between knowledge and behavior (r = .70, p < .05), a medium association between knowledge and attitude (r = .41, p < .05), and a small association between attitude and behavior (r = .21, p < .05). This suggests that strength and conditioning coaches and health staff need to educate and monitor hydration behaviors among collegiate track and field throwers to optimize performance.

Noninvasive Estimation of Hydration Status in Athletes Using Wearable Sensors and a Data-Driven Approach Based on Orthostatic Changes

Dehydration beyond 2% bodyweight loss should be monitored to reduce the risk of heat-related injuries during exercise. However, assessments of hydration in athletic settings can be limited in their accuracy and accessibility. In this study, we sought to develop a data-driven noninvasive approach to measure hydration status, leveraging wearable sensors and normal orthostatic movements. Twenty participants (10 males, 25.0 ± 6.6 years; 10 females, 27.8 ± 4.3 years) completed two exercise sessions in a heated environment: one session was completed without fluid replacement. Before and after exercise, participants performed 12 postural movements that varied in length (up to 2 min). Logistic regression models were trained to estimate dehydration status given their heart rate responses to these postural movements. The area under the receiver operating characteristic curve (AUROC) was used to parameterize the model's discriminative ability. Models achieved an AUROC of 0.79 (IQR: 0.75, 0.91) when discriminating 2% bodyweight loss. The AUROC for the longer supine-to-stand postural movements and shorter toe-touches were similar (0.89, IQR: 0.89, 1.00). Shorter orthostatic tests achieved similar accuracy to clinical tests. The findings suggest that data from wearable sensors can be used to accurately estimate mild dehydration in athletes. In practice, this method may provide an additional measurement for early intervention of severe dehydration.

Effects of Ultratrail Running on Neuromuscular Function, Muscle Damage and Hydration Status. Differences According to Training Level

The status of trail running races has exponentially grown in recent years. The present study aimed to: (a) evaluate the acute response of ultratrail racing in terms of neuromuscular function, muscle damage and hydration status; (b) analyze if responses could differ according to training levels. Twenty runners participated in the present study. The participants were divided into amateur training level (n = 10; 43.30 ± 4.52 years) or high level competitors (n = 10; 41.40 ± 6.18). Neuromuscular response (squat jump, countermovement jump and Abalakov jump), muscle damage (alanine aminotransferase, bilirubin, creatine kinase and leukocytes) and hydration status (sodium and creatinine) were evaluated before and after the Guara Somontano Ultratrail Race (108 km distance, with an accumulated slope of 5800 m). The height and power achieved by vertical jumps were lower after the race (p < 0.001). The post-race muscle damage and creatinine parameters increased in both groups (p < 0.001). The high-level group obtained lower percentages of change in squat jump and countermovement jump than the amateur-level group (p < 0.05). However, the increase in creatinine was greater for the high-level group (p < 0.05). Ultratrail racing reduces neuromuscular function and increases muscle damage. High-level runners showed less neuromuscular fatigue compared to amateur ones.

Chronic Ingestion of Bicarbonate-Rich Water Improves Anaerobic Performance in Hypohydrated Elite Judo Athletes: A Pilot Study

In combat sports, anaerobic power and anaerobic capacity determine sport performance and the dominant metabolic pathways. The decline in performance during exercise that is attributed to the cumulative effects of fatigue, including excessive accumulation of metabolites, depletion of energy substrates, and water and electrolyte disturbances, seems to be of greatest significance. In our experiment, we evaluated the effectiveness of three weeks of bicarbonate-rich water ingestion on anaerobic performance in a state of hydration and dehydration in elite judo athletes. Eight male, elite judo athletes participated in two single-blind, repeated-measures trials. They were assigned to two hydration protocols, ingesting low mineralized table water and bicarbonate-rich water. Anaerobic performance was evaluated by two 30 s Wingate tests for lower and upper limbs, respectively, under conditions of hydration as well as exercise-induced dehydration. Resting, post-ingestion, and post-exercise concentrations of bicarbonate (HCO₃), urine osmolality (U_OSM), urine specific gravity (U_GRAV), and lactate (La) were measured. The current investigation assessed two related factors that impair anaerobic performance-hypohydration and buffering capacity. High-bicarbonate water ingestion improved buffering capacity, and we demonstrated the potential role of this mechanism and its phenomenon in masking the adverse effects of dehydration in the context of repeated high-intensity anaerobic exercise (HIAE).

Validity of water compartments estimated using bioimpedance spectroscopy in athletes differing in hydration status

We aimed to validate bioelectrical impedance spectroscopy (BIS), compared with tracer dilution measurements, for assessing total body water (TBW), intracellular water (ICW), and extracellular water (ECW) in athletes differing in hydration status. A total of 201 athletes participated. Reference TBW and ECW were determined by deuterium and bromide dilution methods, respectively; ICW was calculated as TBW-ECW. Water compartments were estimated by BIS. Urine specific gravity (USG) classified athletes into well-hydrated (WH) (USG < 1.023), euhydrated (EH) (USG:1.024-1.026), and dehydrated (DH) (USG>1.027). No significant differences were found between BIS and the reference methods for WH, EH, and DH athletes for TBW, ICW nor ECW (p>0.05). Concordance of TBW and its compartments by method was significant (p < 0.001) with coefficients of determination ranging by hydration classification [EH:52-96%;DH:56-98%;WH:71-96%]. Bland-Altman analyses showed no trend for TBW and its compartments with the exception of ICW in the WH athletes. The 95% confidence BIS intervals for the WH group ranged from -3.08 to 2.68 kg for TBW, -4.28 to 4.14 kg for ICW, and -3.29 to 3.02 kg for ECW. For the EH athletes, the 95% confidence intervals ranged from -2.78 to 2.24 kg for TBW, -4.10 to 3.94 kg for ICW, and -3.44 to 3.06 kg for ECW. In DH group, TBW ranged between -1.99 and 2.01 kg, ICW between -3.78 and 6.34 kg, and ECW between -6.22 and 3.74 kg. These findings show that BIS is useful at a group level in assessing water compartments in athletes differing in hydration status. However, the usefulness of BIS is limited at an individual level, especially in dehydrated athletes.

Physical performance and loading for six playing positions in elite female football: full-game, end-game, and peak periods

The present study investigated the position-specific match demands and heart rate response of female elite footballers, with special focus on the full-game, end-game, and peak-intensity periods. In total, 217 match observations were performed in 94 players from all eight teams of the best Danish Women's League, that is, goalkeepers (GK, n = 10), central defenders (CD, n = 23), full-backs (FB, n = 18), central midfielders (CM, n = 28), external midfielders (EM, n = 18), and forwards (FW, n = 11). Positional data (GPS; 10 Hz Polar Team Pro) and HR responses were collected. HR_mean and HR_peak were 87%-89% and 98%-99% of HR_max , for outfield players, with no positional differences. CM, EM, and FB covered 8%-14% greater (P < .001) match distances than CD. EM, FW, FB, and CM performed 40%-64% more (P < .05) high-speed running and 41%-95% more (P < .01) very-high-speed running (VHSR) than CD. From the first to the last 15-minute period, total distance, except for FW, number of VHSR, except FB, peak speed and sum of accelerations and sum of decelerations decreased (P < .05) for all outfield positions. In the most intense 5-minute period, EM, FB, and CM performed 25%-34% more (P < .01) HSR than CD, whereas EM, FW, and FB performed 36%-49% more (P < .01) VHSR than CD. In conclusion, competitive elite female matches impose high physical demands on all outfield playing positions, with high aerobic loading throughout matches and marked declines in high-speed running and intense accelerations and decelerations toward the end of games. Overall physical match demands are much lower for central defenders than for the other outfield playing positions, albeit this difference is minimized in peak-intensity periods.

Rehydration during Endurance Exercise: Challenges, Research, Options, Methods

During endurance exercise, two problems arise from disturbed fluid-electrolyte balance: dehydration and overhydration. The former involves water and sodium losses in sweat and urine that are incompletely replaced, whereas the latter involves excessive consumption and retention of dilute fluids. When experienced at low levels, both dehydration and overhydration have minor or no performance effects and symptoms of illness, but when experienced at moderate-to-severe levels they degrade exercise performance and/or may lead to hydration-related illnesses including hyponatremia (low serum sodium concentration). Therefore, the present review article presents (a) relevant research observations and consensus statements of professional organizations, (b) 5 rehydration methods in which pre-race planning ranges from no advanced action to determination of sweat rate during a field simulation, and (c) 9 rehydration recommendations that are relevant to endurance activities. With this information, each athlete can select the rehydration method that best allows her/him to achieve a hydration middle ground between dehydration and overhydration, to optimize physical performance, and reduce the risk of illness.

Evidence that variations in pre-training hydration status are related to the frequency of endurance training in elite adolescent sprinters

BACKGROUND

Although the effect of dehydration on performance is widely studied, limited data concerning the levels of risk training types pose to hydration status exists. This study sought to determine: (a) pre-training hydration status in adolescent sprinters relative to non-athletes, (b) changes in hydration markers across a season of adolescent sprinters relative to non-athletes, and (c) if frequency of training type explains unique variance in hydration.

METHODS

Hydration [via pre-training urine osmolality (UOsm) and thirst perception (TP)], daily water intake (TWI) [via 24-h food/fluid diaries] and frequencies of resistance, endurance and sprint training types (via training regime questionnaires) were assessed in 26 sprinters (age: 15.6±1.9 years) and 26 non-athletes (age: 16.0±1.6 years), during 4 mesocycles [general (T1) and specific (T2) preparation; pre-competitive (T3) and peaking (T4) phases], over 26 weeks.

RESULTS

Most athletes (62%-81%) and non-athletes (73%-92%) were underhydrated (UOsm>700 mOsmol/kg) pre-training across the season, despite a low TP. There were significant time (p =.042) and group (p =.006) effects, and a main group by time interaction for UOsm (p =.006) but not TP across the season, after controlling for TWI. Greater UOsm (in mOsmol/kg) were observed during T1 (906.3±250.1) and T2 (934.5±257.0) compared to T3 (852.1±268.8) and T4 (854.2±218.8). There was no significant change across the season for non-athletes. Frequencies of endurance training were positively associated with UOsm and explained unique variances across the season (R2 range from 7%-16%).

CONCLUSIONS

Underhydration is high in the adolescent population. Training type may be related to the variations in hydration throughout a season, which may help to inform hydration practices of sprint athletes.

Predictors of Athlete's Performance in Ultra-Endurance Mountain Races

Background: In previous studies, ultra-endurance performance has been associated with training and psychological variables. However, performance under extreme conditions is understudied, mainly due to difficulties in making field measures. Aim: The aim of this study was to analyze the role of training, hydration, nutrition, oral health status, and stress-related psychological factors in athletes’ performance in ultra-endurance mountain events. Methods: We analyzed the variables of race time and training, hydration state, nutrition, oral health status, and stress-related psychological factors in 448 ultra-endurance mountain race finishers divided into three groups according to race length (less than 45 km, 45–90 km, and greater than 90 km), using a questionnaire. Results: Higher performance in ultra-endurance mountain races was associated with better oral health status and higher accumulative altitude covered per week as well as higher positive accumulative change of altitude per week during training. In longer distance races, experience, a larger volume of training, and better hydration/nutrition prior to the competition were associated with better performance. Conclusions: Ultra-endurance mountain athletes competing in longer races (>90 km) have more experience and follow harder training schedules compared with athletes competing in shorter distances. In longer races, a larger fluid intake before the competition was the single best predictor of performance. For races between 45 and 90 km, training intensity and volume were key predictors of performance, and for races below 45 km, oral health status was a key predictor of performance. Psychological factors previously reported as ultra-endurance mountain race performance predictors were inconsistent or failed to predict the performance of athletes in the present research.

Different Waters for Different Performances: Can We Imagine Sport-Related Natural Mineral Spring Waters?

Preserving the hydration status means to balance daily fluids and salt losses with gains, where the losses depend on several physiological and environmental factors. Especially for athletes, these losses could be relevant and negatively influence the performance: therefore, their hydro-saline status must be preserved with personalized pre- and rehydration plans all along the performance period. Scientific literature in this field is mainly dedicated to artificial sport drinks. Different territories in most world areas are rich in drinking natural mineral spring waters with saline compositions that reflect their geological origin and that are used for human health (often under medical prescription). However, scarce scientific attention has been dedicated to the use of these waters for athletes. We therefore reviewed the existing literature from the innovative viewpoint of matching spring water mineral compositions with different athletic performances and their hydro-saline requirements.

Practices of Athletic Trainers Using Weight Charts to Determine Hydration Status and Fluid-Intervention Strategies

CONTEXT

Determining an athlete's hydration status allows hydration-related concerns to be identified before significant medical or performance concerns arise. Weight charts are an accurate measure of hydration status changes, yet their clinical use by athletic trainers (ATs) is unknown.

OBJECTIVE

To investigate ATs' use of weight charts in athletic settings and describe their subsequent clinical decisions.

DESIGN

Cross-sectional survey.

SETTING

High schools and National Collegiate Athletic Association Divisions I, II, III and National Association Intercollegiate Athletics colleges.

PATIENTS OR OTHER PARTICIPANTS

A total of 354 ATs (men = 162, women = 175; 17 respondents did not answer the demographic questions) responded across athletic settings (Division I [45.7%]; Division II, Division III, National Association Intercollegiate Athletics combined [n = 19.9%]; and high school [34.4%]).

MAIN OUTCOME MEASURE(S)

The 26-question online survey was developed by content experts and pilot tested before data collection. Participants answered questions focused on weight-chart use (implementation, timing, and calculations) and clinical decision processes (policies, interventions, and referral). Frequency statistics were calculated.

RESULTS

The majority of ATs (57.2%) did not use weight charts. Of those who did, most (76.0%) used charts with football, soccer (28%), and wrestling (6%) athletes. They calculated changes as either an absolute (42.2%) or percentage (36.7%) change from prepractice to postpractice; only 11.7% used a baseline weight for calculations. Of those who used the percentage change in body mass, 66.0% selected a threshold of -3% to -4% for an intervention. Most ATs (97.0%) intervened with verbal education, whereas only one-third (37.0%) provided specific fluid amounts based on body mass changes.

CONCLUSIONS

Typically, ATs in athletic settings did not use weight charts. They considered a body mass change of -3% the indication for intervention but did not specify rehydration amounts for hypohydrated athletes. Educational workshops or technology applications could be developed to encourage ATs to use weight charts and calculate appropriate individual fluid interventions for their athletes.

The Effect of Training Status on Adaptations to 11 Weeks of Block Periodization Training

Some controversy exists as to the most efficacious method of training to achieve enhanced levels of sport performance. Controversy concerning the efficacy of periodization and especially block periodization (BP) likely stems from the use of poorly or untrained subjects versus trained who may differ in their responses to a stimulus. The purpose of this study was to investigate the effect of training status on performance outcomes resulting from 11 weeks of BP training. Fifteen males were recruited for this study and placed into strong (age = 24.3 ± 1.9 years., body mass (BM) = 87.7 ± 8.7 kg, squat: body mass = 1.96 ± 0.16), moderate (age = 25.3 ± 2.7 years., body mass = 100.2 ± 15.5 kg, squat: body mass = 1.46 ± 0.14), or weak (age = 23.2 ± 3.9 yrs., body mass = 83.5 ± 17.1 kg, squat: body mass = 1.17 ± 0.07) groups based on relative strength. Testing was completed at baseline, and after each block which consisted of 1 repetition maximum (1RM) squat, 0 kg static jump (SJ), 0 kg countermovement jump (CMJ), 20 kg SJ, and 20 kg CMJ. Absolute and relative strength were strongly correlated with rates of improvement for absolute strength, relative strength, 0 kg, and 20 kg vertical jumps. All subjects substantially improved back squat (p < 0.001), relative back squat (p < 0.001) with large–very large effect sizes between groups for percent change favoring the weak group over the moderate and strong group for all performance variables. All subjects showed statistically significant improvements in 0 kg SJ (p < 0.001), 0 kg CMJ (p < 0.001), 20 kg SJ (p = 0.002), and 20 kg CMJ (p < 0.001). Statistically significant between group differences were noted for both 20 kg SJ (p = 0.01) and 20 kg CMJ (p = 0.043) with the strong group statistically greater jump heights than the weak group. The results of this study indicate BP training is effective in improving strength and explosive ability. Additionally, training status may substantially alter the response to a resistance training program.

The Impact of a Motor Imagery-Based Training Program on Agility, Speed, and Reaction Time in a Sample of Young Tennis Athletes during Ramadan Fasting: Insights and Implications from a Randomized, Controlled Experimental Trial

The objective of this study was to explore whether a training program incorporating motor imagery could have an effect on physical performance outcomes in terms of agility, speed, and reaction time in a sample of tennis athletes who fasted during the month of Ramadan. Recruited subjects were 27 young male tennis players, randomly allocated to two groups: the imaging training group (n = 13) and a control group (n = 14). The study was designed as a randomized, controlled experimental study. The control group was engaged in watching videos concerning the history of the Olympic Games, whereas the motor imagery group followed a motor imagery-based training program. Physical performance outcomes were assessed during four sessions (one before Ramadan and three during Ramadan) by means of field tests. Our results revealed a drop in all performance outcomes measured in the middle and at the end of Ramadan for both groups (p < 0.01). The effect of the group × time interaction (p < 0.01) was reported for all physical performance outcomes measured for the two groups. This drop in performance was greater for the control group compared to the motor imagery group in the middle and at the end of Ramadan. This study showed that fasting during Ramadan reduced agility, speed, and reaction time performance for tennis players. A motor imagery-based training program could be an effective approach to reduce the effect of fasting during Ramadan and stabilize physical performance outcomes in terms of agility, speed, and reaction time for male tennis players.

UEFA expert group statement on nutrition in elite football. Current evidence to inform practical recommendations and guide future research

Football is a global game which is constantly evolving, showing substantial increases in physical and technical demands. Nutrition plays a valuable integrated role in optimising performance of elite players during training and match-play, and maintaining their overall health throughout the season. An evidence-based approach to nutrition emphasising, a 'food first' philosophy (ie, food over supplements), is fundamental to ensure effective player support. This requires relevant scientific evidence to be applied according to the constraints of what is practical and feasible in the football setting. The science underpinning sports nutrition is evolving fast, and practitioners must be alert to new developments. In response to these developments, the Union of European Football Associations (UEFA) has gathered experts in applied sports nutrition research as well as practitioners working with elite football clubs and national associations/federations to issue an expert statement on a range of topics relevant to elite football nutrition: (1) match day nutrition, (2) training day nutrition, (3) body composition, (4) stressful environments and travel, (5) cultural diversity and dietary considerations, (6) dietary supplements, (7) rehabilitation, (8) referees and (9) junior high-level players. The expert group provide a narrative synthesis of the scientific background relating to these topics based on their knowledge and experience of the scientific research literature, as well as practical experience of applying knowledge within an elite sports setting. Our intention is to provide readers with content to help drive their own practical recommendations. In addition, to provide guidance to applied researchers where to focus future efforts.

Impact of Mild Hypohydration on 100 m Front Crawl Performance and Starting Block Peak Force Production in Competitive University-Level Swimmers

Unstructured, ad libitum drinking may predispose some athletes to start exercise already slightly hypohydrated (decreased body water). The impact of pre-exercise mild hypohydration on subsequent swimming performance is still unknown. Hence, the goal of this study was to examine its effect on peak force production on the starting block and 100 m front crawl swimming performance in competitive university-level swimmers. At least one hour after having been passively exposed to heat where a body mass loss of 1.5% was induced or euhydration (normal body water) maintained, nine participants (age: 22 ± 2 years) underwent an assessment of their peak force production on the starting block and 100 m front crawl performance. One hour following hypohydration, rectal temperature had returned to baseline in each condition. Urine osmolality and specific gravity were higher (p < 0.05) with hypohydration than euhydration (995 ± 65 vs. 428 ± 345 mOsmol/kg; 1.027 ± 0.003 vs. 1.016 ± 0.007 g/mL) prior to exercise testing, as was perceived thirst. Swimming performance (p = 0.86) and peak force production (p = 0.72) on the starting block did not differ between the hypohydration and euhydrated condition (63.00 ± 4.26 vs. 63.09 ± 4.52 s; 1322 ± 236 vs. 1315 ± 230 N). The current results indicate that mild hypohydration, which may occur with ad libitum drinking, does not impede peak force production on the starting block and 100 m front crawl performance in university-level competitive swimmers. Planned drinking is not required prior to such an event.

The Effect of Acute Hypohydration on Indicators of Glycemic Regulation, Appetite, Metabolism and Stress: A Systematic Review and Meta-Analysis

Evidence synthesizing the effects of acute body water losses on various markers of glycemic regulation, appetite, metabolism, and stress is lacking. Thus, the purpose of this review was to summarize the response of various hormonal changes involved in these physiologic functions to dehydration. A comprehensive literature search for peer-reviewed research in the databases PubMed, Scopus, CINAHL, and SportDiscus was conducted. Studies were included if they contained samples of adults (>18 years) and experimentally induced dehydration as measured by acute body mass loss. Twenty-one articles were eligible for inclusion. Findings suggested cortisol is significantly elevated with hypohydration (standard mean difference [SMD] = 1.12, 95% CI [0.583, 1.67], p < 0.0001). Testosterone was significantly lower in studies where hypohydration was accompanied by caloric restriction (SMD= -1.04, 95% CI [-1.93, -0.14], p = 0.02), however, there were no changes in testosterone in studies examining hypohydration alone (SMD = -0.17, 95% CI [-0.51 0.16], p = 0.30). Insulin and ghrelin were unaffected by acute total body water losses. Acute hypohydration increases markers of catabolism but has a negligible effect on markers of glycemic regulation, appetite, anabolism and stress. Given the brevity of existing research, further research is needed to determine the impact of hydration on glucagon, leptin, peptide YY and the subsequent outcomes relevant to both health and performance.

Effects of Motor Mental Imagery Training on Tennis Service Performance during the Ramadan Fasting: a Randomized, Controlled Trial

The objective of the present study is to analyze the effects of motor mental imagery training on tennis service performance among tennis athletes who fast during Ramadan. Participants were 38 young male tennis players, randomly divided into two groups: Imaging Training (IMG, n = 18) and control group (CG, n = 20). The CG has watched videos on the history of the Olympic Games, while IMG has followed a training program in motor imagery. The performance of the tennis service was obtained by the product between accuracy and speed of typing (accuracy × average speed of all shots (km/h)). The effect of group/time interaction (p < 0.01) was identified for all performance indicators (accuracy, running speed and performance (speed × precision)), with improvement only in IMG (p = 0.01). The results showed that motor imagery training could be an effective strategy for mitigating/counteracting the negative effects of Ramadan on the tennis service performance.

The Effects of Dehydration on Metabolic and Neuromuscular Functionality During Cycling

This study aimed to determine the effects of dehydration on metabolic and neuromuscular functionality performance during a cycling exercise. Ten male subjects (age 23.4 ± 2.7 years; body weight 74.6 ± 10.4 kg; height 177.3 ± 4.6 cm) cycled at 65% VO_2max for 60 min followed by a time-to-trial (TT) at 95% VO_2max, in two different conditions: dehydration (DEH) and hydration (HYD). The bioelectrical impedance vector analysis (BIVA) and body weight measurements were performed to assess body fluid changes. Heart rate (HR), energy cost, minute ventilation, oxygen uptake, and metabolic power were evaluated during the experiments. In addition, neuromuscular activity of the vastus medialis and biceps femoris muscles were assessed by surface electromyography. After exercise induced dehydration, the bioimpedance vector significantly lengthens along the major axis of the BIVA graph, in conformity with the body weight change (-2%), that indicates a fluid loss. Metabolic and neuromuscular parameters significantly increased during TT at 95% VO_2max with respect to constant workload at 65% of VO_2max. Dehydration during a one-hour cycling test and subsequent TT caused a significant increase in HR, while neuromuscular function showed a lower muscle activation in dehydration conditions on both constant workload and on TT. Furthermore, a significant difference between HYD and DEH for TT duration was found.

The Predictive Role of Raw Bioelectrical Impedance Parameters in Water Compartments and Fluid Distribution Assessed by Dilution Techniques in Athletes

The aims of this study were to analyze the usefulness of raw bioelectrical impedance (BI) parameters in assessing water compartments and fluid distribution in athletes. A total of 202 men and 71 female athletes were analyzed. Total body water (TBW) and extracellular water (ECW) were determined by dilution techniques, while intracellular water (ICW) was calculated. Fluid distribution was calculated as the ECW/ICW ratio (E:I). Phase angle (PhA), resistance (R) and reactance (Xc) were obtained through BI spectroscopy using frequency 50kHz. Fat (FM) and fat-free mass (FFM) were assessed by dual-energy X-ray absorptiometry. After adjusting for height, FM, FFM, age and sports category we observed that: PhA predicted ICW (females: β = 1.62, p < 0.01; males: β = 2.70, p < 0.01) and E:I (males and females: β = −0.08; p < 0.01); R explained TBW (females: β = −0.03; p < 0.01; males: β = −0.06; p < 0.01) and ECW (females: β = –0.02, p < 0.01; males: β = −0.03, p < 0.01) and ICW (females: β = –0.01, p < 0.053; males: β = –0.03 p < 0.01); and Xc predicted ECW (females: β = −0.06, p < 0.01; males: β = −0.12, p < 0.01). A higher PhA is a good predictor of a larger ICW pool and a lower E:I, regardless of body composition, age, height, and sports category. Lower R is associated with higher water pools whereas ECW expansion is explained by lower Xc. Raw BI parameters are useful predictors of total and extracellular pools, cellular hydration and fluid distribution in athletes.