The Reliability and Validity of a Portable Three-Dimensional Scanning System to Measure Leg Volume.

(1) Background: The study examined the reliability (test-retest, intra- and inter-day) and validity of a portable 3D scanning method when quantifying human leg volume. (2) Methods: Fifteen males volunteered to participate (age, 24.6 ± 2.0 years; stature, 178.9 ± 4.5 cm; body mass, 77.4 ± 6.5 kg; mean ± standard deviation). The volume of the lower and upper legs was examined using a water displacement method (the criterion) and two consecutive 3D scans. Measurements were taken at baseline, 1 h post-baseline (intra-day) and 24 h post-baseline (inter-day). Reliability and validity of the 3D scanning method was assessed using Bland-Altman limits of agreement and Pearson's product moment correlations. (3) Results: With respect to the test-retest reliability, the 3D scanning method had smaller systematic bias and narrower limits of agreement (±1%, and 3-5%, respectively) compared to the water displacement method (1-2% and 4-7%, respectively), when measuring lower and upper leg volume in humans. The correlation coefficients for all reliability comparisons (test-retest, intra-day, inter-day) would all be regarded as 'very strong' (all 0.94 or greater). (4) Conclusions: The study's results suggest that a 3D scanning method is a reliable and valid method to quantify leg volume.

Training and Match Demands of Elite Rugby Union.

ABSTRACT: Cousins, BEW, Morris, JG, Sunderland, C, Bennett, AM, Shahtahmassebi, G, and Cooper, SB. Training and match demands of elite rugby union. J Strength Cond Res 37(1): 141-148, 2023-This study aimed to examine training and match demands associated with elite Rugby Union. Eighty-nine elite players were monitored using subjective (session ratings of perceived exertion) and objective (global positioning systems: distance and high-speed running [defined as >70% of individual maximum speed] distance) methods, alongside key performance indicator variables in matches (e.g., number of tackles made). These were compared between positions (forwards vs. backs) and league of competition (Premiership vs. Championship). Statistical significance was accepted as p < 0.05. Analysis revealed that backs covered greater distance (by 704 m, p < 0.001) in training and greater distance (by 7.6 m·min-1, p < 0.001) and high-speed running distance (by 1.22 m·min-1, p < 0.001) in matches, compared with forwards. In matches, the forwards experience greater key performance indicator demand (tackles: 78%; tackle assists: 207%; breakdown entries: 324%; contact events: 117%; all p < 0.001) compared with backs. The number of tackles (53%, p < 0.001) and tackles missed (35%, p = 0.001) were greater, whereas contact carries (12%, p = 0.010) and breakdown entries (10%, p = 0.024) were lower, in the Premiership compared with the Championship. Overall, these findings confirm that the running demands of Rugby Union are higher in backs, whereas contact actions are higher in forwards, with further differences between the Premiership and Championship. This comprehensive examination of the demands of elite Rugby Union could be used to ensure the specificity of training protocols for elite Rugby Union clubs, specific to both playing position (forward or back) and level of competition (Premiership or Championship).

Associations of Self-Control with Physical Activity, Physical Fitness, and Adiposity in Adolescents.

The associations between self-control and objective measures of physical activity, physical fitness, and adiposity are yet to be explored in young people; this is a gap in the literature that the present study aimed to address. The study employed a cross-sectional design. A total of 101 young people participated in the study. Participants completed the Brief Self-Control Scale as a measure of trait self-control. Free-living physical activity was assessed using an ActiGraph GT3X + triaxial accelerometer, which was worn for 7 days. Participants also completed the 15-meter version of the multistage fitness test as a measure of physical fitness. For the assessment of adiposity, three criterion measures were used: body mass index (BMI), sum of skinfolds, and waist circumference. Data were analyzed using the glm function in the open access software R. Higher levels of trait self-control were associated with higher levels of physical fitness (measured by distance run on the multistage fitness test) and lower adiposity (BMI, waist circumference, and sum of skinfolds) in adolescents. There was a tendency for a positive association between self-control and time spent in vigorous physical activity, although this did not reach statistical significance. In a combined model, self-control was also associated with both physical fitness and waist circumference, with these effects independent of each other. These findings suggest that self-control is associated with healthy behaviors and characteristics in adolescents and is thus potentially an attractive target for future interventions aimed at increasing physical activity and physical fitness and reducing adiposity in this population.

Predictors of postprandial glycaemia, insulinaemia and insulin resistance in adolescents.

Postprandial glycaemia and insulinaemia are important risk factors for type 2 diabetes. The prevalence of insulin resistance in adolescents is increasing, but it is unknown how adolescent participant characteristics such as BMI, waist circumference, fitness and maturity offset may explain responses to a standard meal. The aim of the present study was to examine how such participant characteristics affect the postprandial glycaemic and insulinaemic responses to an ecologically valid mixed meal. Data from the control trials of three separate randomised, crossover experiments were pooled, resulting in a total of 108 participants (fifty-two boys, fifty-six girls; aged 12·5 (SD 0·6) years; BMI 19·05 (SD 2·66) kg/m2). A fasting blood sample was taken for the calculation of fasting insulin resistance, using the homoeostatic model assessment of insulin resistance (HOMA-IR). Further capillary blood samples were taken before and 30, 60 and 120 min after a standardised lunch, providing 1·5 g/kg body mass of carbohydrate, for the quantification of blood glucose and plasma insulin total AUC (tAUC). Hierarchical multiple linear regression demonstrated significant predictors for plasma insulin tAUC were waist circumference, physical fitness and HOMA-IR (F(3,98) = 36·78, P < 0·001, adjusted R2 = 0·515). The variance in blood glucose tAUC was not significantly explained by the predictors used (F(7,94) = 1·44, P = 0·198). Significant predictors for HOMA-IR were BMI and maturity offset (F(2,102) = 14·06, P < 0·001, adjusted R2 = 0·021). In summary, the key findings of the study are that waist circumference, followed by physical fitness, best explained the insulinaemic response to an ecologically valid standardised meal in adolescents. This has important behavioural consequences because these variables can be modified.

Detrimental effects of prior self-control exertion on subsequent sporting skill performance.

The prior exertion of self-control has previously been shown to negatively affect physical performance, yet the effects on complex sporting skill performance have not been examined. Therefore, this study examined whether prior self-control exertion influences performance on a field hockey task, alongside measuring plasma cortisol concentration and attention as potential mechanisms to explain any effects. Following familiarization, 13 male hockey players (20 ± 1 years) participated in a randomized, order-balanced, crossover design. For the manipulation of self-control, participants completed an incongruent (self-control exertion trial) or a congruent (control trial) Stroop task. Skill performance was assessed using a field hockey skills task. Capillary blood samples, for the determination of plasma cortisol concentration, were taken at baseline, post-Stroop task, and post-field hockey skills task. Cognitive tests of attention (RVIP and Flanker tasks) were completed following the field hockey skills task. Participants made more errors in the latter stages of the field hockey skills task following self-control exertion (trial*time interaction, p = 0.041). Participants also made more errors on the RVIP task following self-control exertion (p = 0.035); yet the time taken to complete the hockey skills task, performance on the flanker task, and plasma cortisol concentrations were unaffected (all p > 0.05). Overall, these findings suggest that prior self-control exertion has detrimental effects on subsequent sporting skill performance (more errors made on the field hockey task), which may be explained by poorer sustained attention (lower accuracy on the RVIP task). This suggests that athletes should aim to avoid self-control exertion before a competitive match to optimize performance.

Effect of acute football activity and physical fitness on glycaemic and insulinaemic responses in adolescents.

The present study examined the metabolic responses to an acute bout of football and the overall and moderating role of physical fitness on these responses, in adolescents. Thirty-six adolescents (16 girls, 20 boys; 12.6±0.5 y) completed two trials (60-min football and 60-min seated rest) separated by 7-d. Capillary blood samples were taken at baseline (60-min prior to exercise/rest), immediately, 30- and 60-min post-exercise and 30-, 60- and 120-min following a standardised lunch (1.5-, 2- and 3-h post-exercise), for the determination of blood glucose and plasma insulin concentrations. The median split of distance covered on the multi-stage fitness test was used to define high- and low-fit groups. Overall plasma insulin tAUC following lunch was lower in high-fit participants compared to low-fit (high-fit: 3784.2±1653.1 pmol·L-1x120min, low-fit: 6457.3±3290.7 pmol·L-1x120min; p<0.001), although there was no acute effect of the football session (p>0.05). Football reduced blood glucose concentration 1-h post-exercise compared to control (exercise: 3.8±0.6 mmol·L-1, rest: 4.6±0.8 mmol·L-1; p<0.001), but this was similar for the high- and low-fit participants (p>0.05). Blood glucose tAUC was not affected by exercise or physical fitness (p>0.05). These data emphasise the importance of physical fitness for metabolic health in adolescents, as well as the utility of football as a popular form of games-based activity for improving glucose regulation.

Effect of Changing Match Format from Halves to Quarters on the Performance Characteristics of Male University Field Hockey Players.

The study examined whether the performance characteristics of male university field hockey players differed when the match format was 2 × 35 min halves compared to 2 × 2 × 17.5 min quarters. Thirty-five male university field hockey players (age 21.2 ± 3.0 years, height 1.81 ± 0.07 m, body mass 75.1 ± 8.9 kg), competing at national level in the UK, were monitored over 52 matches played across the 2018-2019 (2 × 35 min halves) and 2019-2020 (2 × 2 × 17.5 min quarters) seasons using 15 Hz Global Positioning System units and heart rate monitors. Total distance, high-speed running distance (≥15.5 km·h-1), accelerations (≥2 m·s-1), decelerations (≤-2 m·s-1), average heart rate and percentage of time spent at >85% of maximum heart rate were recorded during both match formats. Two-level random intercept hierarchal models (Match-level 1, Player-level 2) suggested that the change in format from 2 × 35 min halves (2018-2019 season) to 2 × 2 × 17.5 min quarters (2019-2020 season) resulted in a reduction in total distance and high-speed running distance completed during a match (by 221 m and 120 m, respectively, both p < 0.001). As no significant cross-level interactions were observed (between season and half), the change from 35 min halves to 17.5 min quarters did not attenuate the reduced physical performance evident during the second half of matches (total distance: -235 m less in second half; high-speed running distance: -70 m less in second half; both p < 0.001). Overall, the findings suggest that the change in match format did alter the performance characteristics of male university field hockey players, but the quarter format actually reduced the total distance and high-speed running distance completed during matches, and did not attenuate the reduction in performance seen during the second half of matches.

Effect of football activity and physical fitness on information processing, inhibitory control and working memory in adolescents.

BACKGROUND: Whilst an acute bout of exercise has been shown to enhance subsequent cognition, including in adolescents, the effects of team games (of which Football is the most popular) has received little attention. Therefore, this study examined: the effect of an acute bout of outdoor Football activity on information processing, inhibitory control, working memory and circulating brain-derived neurotrophic factor (BDNF) in adolescents; the effect of physical fitness on cognition and; the moderating effect of physical fitness on the acute exercise responses. METHODS: Following familiarisation, 36 adolescents (16 girls) took part in two trials (60-min Football and 60-min seated rest) separated by 7-d in a counterbalanced, crossover design. Information processing and inhibitory control (Stroop Test), and working memory (Sternberg Paradigm) were assessed 30-min before exercise/rest and immediately, 45- and 90-min post-exercise/rest. Capillary blood samples were obtained before exercise/rest and up to 120-min post-exercise/rest. The median split of distance covered on the MSFT was used to divide the group into high- and low-fit groups. RESULTS: Performance on the cognitive function tasks was similar between Football and seated rest (trial*time interactions; all p > .05). However, the high-fit group had overall quicker response times on both levels of the Stroop Task and all three levels of the Sternberg Paradigm (main effect of fitness; all p < .001). Furthermore, the exercise-cognition relationship was moderated by physical fitness, with improvements in working memory response times seen post-exercise, only in the high-fit group (trial*time*fitness interaction, p < .05). Circulating BDNF was unaffected by the Football activity and physical fitness (p > .05). CONCLUSION: The present study shows that higher levels of physical fitness are beneficial for cognitive function and provides novel evidence that an ecologically valid, and popular, form of exercise is beneficial for working memory following exercise, in high-fit participants only.

Identifying playing talent in professional football using artificial neural networks.

The aim of the current study was to objectively identify position-specific key performance indicators in professional football that predict out-field players league status. The sample consisted of 966 out-field players who completed the full 90 minutes in a match during the 2008/09 or 2009/10 season in the Football League Championship. Players were assigned to one of three categories (0, 1 and 2) based on where they completed most of their match time in the following season, and then split based on five playing positions. 340 performance, biographical and esteem variables were analysed using a Stepwise Artificial Neural Network approach. The models correctly predicted between 72.7% and 100% of test cases (Mean prediction of models = 85.9%), the test error ranged from 1.0% to 9.8% (Mean test error of models = 6.3%). Variables related to passing, shooting, regaining possession and international appearances were key factors in the predictive models. This is highly significant as objective position-specific predictors of players league status have not previously been published. The method could be used to aid the identification and comparison of transfer targets as part of the due diligence process in professional football.

Psychological characteristics of developing excellence in elite youth football players in English professional academies.

This mixed-longitudinal prospective study examined the development of psychological characteristics of developing excellence in relation to the career progression of elite youth football players. In a 20-month period, 111 academy football players aged 11-16 completed the Psychological Characteristics of Developing Excellence Questionnaire (PCDEQ) on 1-5 occasions. This combination of single and repeated assessments resulted in a mixed-longitudinal sample of 226 completed PCDEQs. Players were then prospectively tracked, and their scholarship status assessed at follow-up, at age U17. Multilevel modelling revealed that coping with performance and developmental pressures scores increased with age, and that Category 1-2 academy scholars (4.35 ± 0.61) scored higher than Category 3-4 academy scholars (3.99 ± 0.67) and non-scholars (4.02 ± 0.78) (p < .05). Evaluating performances and working on weaknesses scores increased with age for Category 1-2 academy scholars (U12-U14 vs. U15-U16 = 5.16 ± 0.48 vs. 5.38 ± 0.45), compared to non-scholars (U12-U14 vs. U15-U16 = 5.11 ± 0.59 vs. 5.03 ± 0.71) (p < .05). Imagery use during practice and competition scores decreased with age (U12-U14 vs. U15-U16 = 4.45 ± 0.66 vs. 4.29 ± 0.70) (p < .05). A blend of PCDEs may facilitate optimal career progression. Football academies should develop players' PCDEs, with a particular focus on developing their coping skills and their ability to realistically evaluate performances and work on weaknesses.

Predicting Wins, Losses and Attributes' Sensitivities in the Soccer World Cup 2018 Using Neural Network Analysis.

Predicting the results of soccer competitions and the contributions of match attributes, in particular, has gained popularity in recent years. Big data processing obtained from different sensors, cameras and analysis systems needs modern tools that can provide a deep understanding of the relationship between this huge amount of data produced by sensors and cameras, both linear and non-linear data. Using data mining tools does not appear sufficient to provide a deep understanding of the relationship between the match attributes and results and how to predict or optimize the results based upon performance variables. This study aimed to suggest a different approach to predict wins, losses and attributes' sensitivities which enables the prediction of match results based on the most sensitive attributes that affect it as a second step. A radial basis function neural network model has successfully weighted the effectiveness of all match attributes and classified the team results into the target groups as a win or loss. The neural network model's output demonstrated a correct percentage of win and loss of 83.3% and 72.7% respectively, with a low Root Mean Square training error of 2.9% and testing error of 0.37%. Out of 75 match attributes, 19 were identified as powerful predictors of success. The most powerful respectively were: the Total Team Medium Pass Attempted (MBA) 100%; the Distance Covered Team Average in zone 3 (15-20 km/h; Zone3_TA) 99%; the Team Average ball delivery into the attacking third of the field (TA_DAT) 80.9%; the Total Team Covered Distance without Ball Possession (Not in_Poss_TT) 76.8%; and the Average Distance Covered by Team (Game TA) 75.1%. Therefore, the novel radial based function neural network model can be employed by sports scientists to adapt training, tactics and opposition analysis to improve performance.

Cytokine, glycemic, and insulinemic responses to an acute bout of games-based activity in adolescents.

An acute bout of endurance exercise in adults stimulates a same-day anti-inflammatory response which may affect low-grade chronic inflammation and insulin resistance and benefit cardio-metabolic health. The anti-inflammatory responses to intermittent games-based exercise and to exercise in young people beyond 2 hours post-exercise are unknown. Thus, the purpose of the present study is to examine the anti-inflammatory, glycemic and insulinemic response to games-based activity in adolescents. Following ethical approval and familiarization, 39 adolescents (12.3 ± 0.7 years) completed an exercise (E) and rested (R) trial in a counterbalanced, randomized crossover design. Following a standardized breakfast, participants completed 1-hour games-based activity. Capillary blood samples were taken at baseline, immediately and 1 hour post-exercise, and 30, 60 and 120 minutes following a standardized lunch. A final blood sample was taken the next morning. Data were analyzed using repeated measures ANOVA. IL-6 concentration was higher on day one of the exercise trial (E:3.4 ± 0.4, R:2.7 ± 0.4 pg/mL; P = 0.006), as was the anti-inflammatory IL-6:TNF-α ratio (E:5.53 ± 0.93, R:3.75 ± 0.45; P = 0.027). Levels of the anti-inflammatory cytokine IL-10 increased on day two of the exercise trial (E:2.11 ± 0.23, R:1.66 ± 0.16 pg/mL; P = 0.032). Insulin sensitivity was enhanced on the exercise trial with a reduction in iAUC following the standardized lunch (E:2310 ± 834, R:3122 ± 1443 mU/L × 120 minutes; P < 0.001). Games-based activity stimulated an anti-inflammatory response up to 24 hours post-exercise and improved insulin sensitivity in response to a standardized meal in healthy adolescents. These novel findings suggest that games-based activity is an ecologically valid mode of exercise to elicit beneficial effects on cardio-metabolic risk factors in young people.

Effects of situational variables on the physical activity profiles of elite soccer players in different score line states.

The aim of this study were to investigate the effects of playing position, pitch location, team ability and opposition ability on the physical activity profiles of English premier league soccer players in difference score line states. A validated automatic tracking system (Venatrack Ltd.) was used to track players in real time (at 25 Hz) for total distance covered, high speed running distance and sprint distance. This is the first study to include every team from an entire season in the English premier league, resulting in 376 games, 570 players and 35 000 rows of data from the 2011-12 season being analyzed using multi-level modelling. Multi-level regression revealed an inverted "u" shaped association between total distance covered and goal difference (GD), with greater distances covered when GD was zero and reduced distances when GD was either positive or negative. A similar "u" shaped association was found with high speed distance covered at home. In addition distance covered (both at home and away) were predicted by playing position. All activity profiles (with the exception of sprint distance at home) were predicted by pitch location and time scored. Lastly, distance away from home and high speed running at home were predicted by opposition ability. Score line appears to effect player activity profiles across a number of situational factors and thus should be considered by managers when preparing and selecting teams to maximize performance. The current study also highlighted the need for more sensitive score line definitions in which to consider score line effects.

High intensity intermittent games-based activity and adolescents' cognition: moderating effect of physical fitness.

BACKGROUND: An acute bout of exercise elicits a beneficial effect on subsequent cognitive function in adolescents. The effect of games-based activity, an ecologically valid and attractive exercise model for young people, remains unknown; as does the moderating effect of fitness on the acute exercise-cognition relationship. Therefore, the aim of the present study was to examine the effect of games-based activity on subsequent cognition in adolescents, and the moderating effect of fitness on this relationship. METHODS: Following ethical approval, 39 adolescents (12.3 ± 0.7 year) completed an exercise and resting trial in a counterbalanced, randomised crossover design. During familiarisation, participants completed a multi-stage fitness test to predict VO2 peak. The exercise trial consisted of 60-min games-based activity (basketball), during which heart rate was 158 ± 11 beats∙min- 1. A battery of cognitive function tests (Stroop test, Sternberg paradigm, trail making and d2 tests) were completed 30-min before, immediately following and 45-min following the basketball. RESULTS: Response times on the complex level of the Stroop test were enhanced both immediately (p = 0.021) and 45-min (p = 0.035) post-exercise, and response times on the five item level of the Sternberg paradigm were enhanced immediately post-exercise (p = 0.023). There were no effects on the time taken to complete the trail making test or any outcome of the d2 test. In particular, response times were enhanced in the fitter adolescents 45-min post-exercise on both levels of the Stroop test (simple, p = 0.005; complex, p = 0.040) and on the three item level of the Sternberg paradigm immediately (p = 0.017) and 45-min (p = 0.008) post-exercise. CONCLUSIONS: Games-based activity enhanced executive function and working memory scanning speed in adolescents, an effect particularly evident in fitter adolescents, whilst the high intensity intermittent nature of games-based activity may be too demanding for less fit children.

Activity Profile and Between-Match Variation in Elite Male Field Hockey.

Sunderland, CD and Edwards, PL. Activity profile and between-match variation in elite male field hockey. J Strength Cond Res 31(3): 758-764, 2017-This study aimed to (a) provide a position-specific activity profile for elite male hockey players, (b) determine if the activity profile was altered by the introduction of the "self-pass" rule, and (c) provide information relating to match-to-match variability in elite male field hockey. The activity of 28 elite male field hockey players was analyzed over 2 seasons totaling 395 player-match analyses using Global Positioning Satellite technology. Total distance, high-speed running (>15.5 km·h), sprinting (>20 km·h), and mean speed were recorded. Players were categorized into 4 positions: fullback (FB), halfback (HB), midfield (M), and forward (F). Data were analyzed using a 2-way analysis of variance (season, position) and between-match coefficients of variation (CV). The time played differs with position (FB: 65.5 ± 5.3, HB: 49.5 ± 11.5, M: 45.9 ± 7.1, F: 39.5 ± 5.4 minutes; p < 0.0005) and thus affected the activity profile. Total distance covered was greater for fullbacks (FB: 8,001 ± 447, HB: 6,435 ± 1,399, M: 6,415 ± 908, F: 5,844 ± 762 m, p < 0.001), and mean speed and percentage time spent high-speed running and sprinting were greater for forwards than all other positions (HSR: FB: 6.8 ± 1.0, HB: 8.8 ± 1.3, M: 10.7 ± 1.2, F: 13.5 ± 1.8%, p < 0.001). The activity profile did not differ with the introduction of the self-pass. Match-to-match variability (CV) ranged from 5.0% to 22.0% for total and sprint distance, respectively. This is the first study to present an activity profile of elite men's field hockey and its associated variability and demonstrates that each position is unique, and therefore, training and recovery should be position specific.

Immediate pre-meal water ingestion decreases voluntary food intake in lean young males.

PURPOSE: Consuming 375-500 ml of water 30 min before a meal has been shown to reduce energy intake in older, but not younger adults. This study investigated the effects of ingesting a water preload immediately pre-meal (<1 min before eating) on within-meal ad libitum energy intake in non-obese young males. METHODS: Fourteen healthy males [mean (SD) age 27 (3) years, height 1.83 (0.05) m, body weight 80.47 (9.89) kg, body fat 17.5 (4.0) %, body mass index 24.0 (2.5) kg/m(2)] completed a familiarisation trial and two experimental trials in randomised counterbalanced order. Subjects arrived at the laboratory overnight fasted and consumed an ad libitum porridge breakfast. Immediately prior to the meal, subjects consumed either a 568 ml (1 pint) water preload (preload trial) or no preload (control trial). Visual analogue scale questionnaires to assess hunger, fullness and satisfaction were completed before and after the meal in both trials, as well as after the water preload. RESULTS: Ad libitum energy intake was greater (P < 0.001) during control [2551 (562) kJ] than preload [1967 (454) kJ]. Ad libitum water intake was also greater (P < 0.001) during control [318 (226-975) ml] than preload [116 (0-581) ml]. The water preload increased fullness and satisfaction and decreased hunger compared to pre-trial (P < 0.001) and the control trial (P < 0.001). CONCLUSION: This study demonstrates that consumption of a 568 ml water preload immediately before a meal reduces energy intake in non-obese young males. This might therefore be an effective strategy to suppress energy intake in this population and possibly assist with weight management.

Effect of hydration status and fluid availability on ad-libitum energy intake of a semi-solid breakfast.

This study investigated the effects of hydration status and fluid availability on appetite and energy intake. Sixteen males completed four 24 h trials, visiting the laboratory overnight fasted on two consecutive days. Standardised foods were provided during the 24 h and on day two an ad-libitum semi-solid porridge breakfast was provided. Water intake during the 24 h (0 or 40 mL⋅kg(-1)) and fluid provision during the ad-libitum breakfast were manipulated so subjects were euhydrated with (EU-F) and without fluid (EU-NF) available at breakfast; and hypohydrated with (HYPO-F) and without fluid (HYPO-NF) available at breakfast. Blood samples (0 and 24 h), urine samples (0-24 h) and subjective responses (0, 24 and 24.5 h) were collected. HYPO trials decreased body mass by ~1.8%. Serum and urine osmolality increased and plasma volume decreased during HYPO trials (P <0.001). Total urine output was greater during EU than HYPO trials (P <0.001). Ad-libitum energy intake was not different between trials: 2658 (938) kJ (EU-F), 2353 (643) kJ (EU-NF), 2295 (529) kJ (HYPO-F), 2414 (954) kJ (HYPO-NF), (P = 0.131). Fluid intake was ~200 mL greater during HYPO-F than EU-F (P <0.01). There was an interaction effect for thirst (P < 0.001), but not hunger or fullness. These results demonstrate that mild hypohydration produced by inadequate fluid intake and fluid availability during eating does not influence ad-libitum energy intake of a semi-solid breakfast, at least in healthy young males.

The effect of cooling prior to and during exercise on exercise performance and capacity in the heat: a meta-analysis.

Exercise is impaired in hot, compared with moderate, conditions. The development of hyperthermia is strongly linked to the impairment and as a result various strategies have been investigated to combat this condition. This meta-analysis focused on the most popular strategy: cooling. Precooling has received the most attention but recently cooling applied during the bout of exercise has been investigated and both were reviewed. We conducted a literature search and retrieved 28 articles which investigated the effect of cooling administered either prior to (n=23) or during (n=5) an exercise test in hot (wet bulb globe temperature >26°C) conditions. Mean and weighted effect size (Cohen's d) were calculated. Overall, precooling has a moderate (d=0.73) effect on subsequent performance but the magnitude of the effect is dependent on the nature of the test. Sprint performance is impaired (d=-0.26) but intermittent performance and prolonged exercise are both improved following cooling (d=0.47 and d=1.91, respectively). Cooling during exercise has a positive effect on performance and capacity (d=0.76). Improvements were observed in studies with and without cooling-induced physiological alterations, and the literature supports the suggestion of a dose-response relationship among cooling, thermal strain and improvements in performance and capacity. In summary, precooling can improve subsequent intermittent and prolonged exercise performance and capacity in a hot environment but sprint performance is impaired. Cooling during exercise also has a positive effect on exercise performance and capacity in a hot environment.

The effect of hydration status on appetite and energy intake.

This study investigated the effect of hypohydration produced by exercise and sub-optimal rehydration on appetite and energy intake. Ten males lost ~2% body mass through evening exercise in the heat (35°C). Over the next 13 h, participants were re-fed and either rehydrated (RE: water equal to 175% of body mass loss (BML)) or remained hypohydrated (HYPO: 200 ml water), until the following morning. Urine samples, blood samples and subjective feelings were collected pre-exercise, post-exercise and 13 h post-exercise, with an ad libitum breakfast provided 13 h post-exercise. Total BML at 13 h post-exercise was greater during HYPO (2.8 (0.5)%) than RE (0.5 (0.5)%). Energy intake at the ad libitum breakfast was similar between trials (RE: 4237 (1459) kJ; HYPO: 4612 (1487) kJ; P = 0.436), with no difference in energy consumed in foods (P = 0.600) or drinks (P = 0.147). Total water ingestion at the ad libitum breakfast meal was greater during HYPO (1641 (367) ml) than RE (797 (275) ml) (P < 0.001), with this being explained by increased water intake through fluids (P < 0.001). Thirteen hours post-exercise, participants reported greater thirst (P < 0.001) and lower fullness (P < 0.01) during HYPO. Alterations in hydration status produced by exercise are unlikely to influence post-exercise food intake and consequently other aspects of recovery or adaptation.