PGC-1α alternative promoter (Exon 1b) controls augmentation of total PGC-1α gene expression in response to cold water immersion and low glycogen availability.

This investigation sought to determine whether post-exercise cold water immersion and low glycogen availability, separately and in combination, would preferentially activate either the Exon 1a or Exon 1b Peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) promoter. Through a reanalysis of sample design, we identified that the systemic cold-induced augmentation of total PGC-1α gene expression observed previously (Allan et al. in J Appl Physiol 123(2):451-459, 2017) was largely a result of increased expression from the alternative promoter (Exon 1b), rather than canonical promoter (Exon 1a). Low glycogen availability in combination with local cooling of the muscle (Allan et al. in Physiol Rep 7(11):e14082, 2019) demonstrated that PGC-1α alternative promoter (Exon 1b) expression continued to rise at 3 h post-exercise in all conditions; whilst, expression from the canonical promoter (Exon 1a) decreased between the same time points (post-exercise-3 h post-exercise). Importantly, this increase in PGC-1α Exon 1b expression was reduced compared to the response of low glycogen or cold water immersion alone, suggesting that the combination of prior low glycogen and CWI post-exercise impaired the response in gene expression versus these conditions individually. Data herein emphasise the influence of post-exercise cooling and low glycogen availability on Exon-specific control of total PGC-1 α gene expression and highlight the need for future research to assess Exon-specific regulation of PGC-1α.

TRIM63 (MuRF-1) gene polymorphism is associated with biomarkers of exercise-induced muscle damage.

Unaccustomed strenuous exercise can lead to muscle strength loss, inflammation and delayed-onset muscle soreness, which may be influenced by genetic variation. We investigated if a missense single nucleotide polymorphism (A>G, rs2275950 ) within the TRIM63 gene (encoding MuRF-1 and potentially affecting titin mechanical properties) was associated with the variable response to unaccustomed eccentric exercise. Sixty-five untrained, healthy participants (genotyped for rs2275950 : AA, AG, and GG) performed 120 maximal eccentric knee extensions (ECC) to induce muscle damage. Isometric and isokinetic maximal voluntary knee extension contractions (MVCs) and muscle soreness were assessed before, immediately after, and 48 h after ECC. AA homozygotes were consistently stronger [baseline isometric MVC: 3.23 ± 0.92 Nm/kg (AA) vs. 2.09 ± 0.67 Nm/kg (GG); P = 0.006] and demonstrated less muscle soreness over time ( P = 0.022) compared with GG homozygotes. This may be explained by greater titin stiffness in AA homozygotes, leading to intrinsically stronger muscle fibers that are more resistant to eccentric damaging contractions.

Variations of collagen-encoding genes are associated with exercise-induced muscle damage.

We investigated whether single nucleotide polymorphisms (SNPs) within genes encoding the alpha-1 chain of type I ( COL1A1, rs2249492 ; rs1800012 ), type II ( COL2A1, rs2070739 ), and type V (COL5A1, rs12722 ) collagen were associated with the variable response to exercise-induced muscle damage (EIMD). Knee extensor muscle strength and soreness were assessed pre-, post-, and 48 h post-EIMD (120 maximal eccentric knee extensor contractions) in 65 young healthy participants, who were genotyped for the aforementioned SNPs. We found that COL1A1 (minor) T-allele carriers ( rs1800012 ) and (major) T-allele homozygotes ( rs2249492 ) were generally weaker ( P ≤ 0.019); and (minor) A-allele carriers of COL2A1 ( P = 0.002) and (major) T-allele carriers of COL5A1 ( P = 0.004) SNPs reported greater muscle soreness, all compared with their respective major ( rs1800012 ; rs2070739 ) and minor ( rs2249492 ; rs12722 ) allele homozygote counterparts. To conclude, the risk alleles of these four SNPs appear to negatively influence muscle strength and post-EIMD recovery, possibly via a dysregulated collagen network affecting the muscle's mechanical properties.

Passive and post-exercise cold-water immersion augments PGC-1α and VEGF expression in human skeletal muscle.

PURPOSE: We tested the hypothesis that both post-exercise and passive cold water immersion (CWI) increases PGC-1α and VEGF mRNA expression in human skeletal muscle. METHOD: Study 1 Nine males completed an intermittent running protocol (8 × 3-min bouts at 90 % [Formula: see text], interspersed with 3-min active recovery (1.5-min at 25 % and 1.5-min at 50 % [Formula: see text]) before undergoing CWI (10 min at 8 °C) or seated rest (CONT) in a counterbalanced, randomised manner. Study 2 Ten males underwent an identical CWI protocol under passive conditions. RESULTS: Study 1 PGC-1α mRNA increased in CONT (~3.4-fold; P < 0.001) and CWI (~5.9-fold; P < 0.001) at 3 h post-exercise with a greater increase observed in CWI (P < 0.001). VEGFtotal mRNA increased after CWI only (~2.4-fold) compared with CONT (~1.1-fold) at 3 h post-exercise (P < 0.01). Study 2 Following CWI, PGC-1α mRNA expression was significantly increased ~1.3-fold (P = 0.001) and 1.4-fold (P = 0.0004) at 3 and 6 h, respectively. Similarly, VEGF165 mRNA was significantly increased in CWI ~1.9-fold (P = 0.03) and 2.2-fold (P = 0.009) at 3 and 6 h post-immersion. CONCLUSIONS: Data confirm post-exercise CWI augments the acute exercise-induced expression of PGC-1α mRNA in human skeletal muscle compared to exercise per se. Additionally CWI per se mediates the activation of PGC-1α and VEGF mRNA expression in human skeletal muscle. Cold water may therefore enhance the adaptive response to acute exercise.

The challenge and impact of engaging hard-to-reach populations in regular physical activity and health behaviours: an examination of an English Premier League 'Football in the Community' men's health programme.

OBJECTIVES: To investigate the challenges that men from hard-to-reach (HTR) populations encounter when attempting to commit to regular participation in physical activity and health behaviours, and to explore the psychological and social effects of participation in a twelve week football-led health improvement intervention. STUDY DESIGN: A twelve week football specific physical activity intervention targeting men from HTR populations was delivered by Everton Football Clubs' Football in the Community (FitC) scheme as part of a national programme of men's health delivered in/by English Premier League (EPL) football clubs. Men living in homeless shelters and/or recovering from substance misuse were recruited over a period of three months. The programme consisted of a two hour football session, twice weekly, alongside the dissemination of healthy living messages. Football sessions were conducted by a qualified FitC coach. METHODS: This research was conducted during a twelve week period of immersed practitioner-research. Ethnographic and observational methodologies were adopted. Psychosocial issues were discussed with participants through informal client-researcher interactions and data were logged via field notes. Records of attendance were logged. Participants who failed to attend a session were contacted and their reason(s) for non-attendance were recorded. Data were analysed using deductive and inductive reasoning. RESULTS: Despite the apparent ambition of the participants to regularly participate in the FitC programme, adherence to the programme was poor. Economic, environmental and social barriers to engagement in the programme were apparent. Engagement in the programme resulted in positive psychosocial developments; the development of structure, social interaction and social capital. CONCLUSION: Community based football-led health improvement programmes endorsed by professional football clubs appear well positioned to connect with, and attract, men from HTR populations. The evidence suggests that such programmes can improve psychosocial health amongst these populations. However, a bottom-up programme design and management strategy is required in order to reduce the challenges facing HTR participants when attempting to regularly engage in physical activity and health behaviours.

Asymmetry after hamstring injury in English Premier League: issue resolved, or perhaps not?

Hamstring injuries constitute one of the most concerning injuries in English Premier League football, due to its high primary incidence but also its recurrence. Functional methods assessing hamstring function during high-risk performance tasks such as sprinting are vital to identify potential risk factors. The purpose of this study was to assess horizontal force deficits during maximum sprint running on a non-motorized treadmill in football players with previous history of hamstring strains as a pre-season risk-assessment in a club setting. 17 male football players from one Premier League Club were divided into 2 groups, experimental (n=6, age=24.5±2.3 years) and control (n=11, age=21.3±1.2 years), according to history of previous hamstring injury. Participants performed a protocol including a 10-s maximum sprint on a non-motorized treadmill. Force deficits during acceleration phase and steady state phases of the sprint were assessed between limbs and between groups. The main outcome measures were horizontal and vertical peak forces during the acceleration phase or steady state. There were no significant differences in peak forces between previously injured and non-injured limbs, or between groups, challenging the ideas around functional force deficits in sprint running as a diagnostic measure of hamstring re-injury risk.

Seasonal changes in multiple indices of body composition in professional football players.

We examined the seasonal variability of indicators of adiposity and generic and population-specific equations of estimating body fat in professional football players. Anthropometric data of 35 outfield players (age, 20±4 years; stature, 1.82±0.06 m; body mass 77.1±7.3 kg) were collected over a playing season. There were a significant main effects for time for all indicators (p<0.001). Post hoc analysis revealed significant changes in body composition between July and mid-August (∑4SF-DW: 1.6 mm, p<0.001; ∑4SF-R: 2.4 mm, p=0.002; ∑5SF: 2.0 mm, p<0.002; ∑8SF: 3.8 mm, p=0.001; Reilly et al.: 0.4%, p=0.001; Durnin and Wormsley: 0.7%, p<0.001). Although all indicators were sensitive to detect small changes in body composition between training mesocycles, we advocate the use of the sum of 4 skinfolds by Reilly et al. to monitor changes in body composition in professional football players; if an estimate of percent body fat is required, the population-specific equation by Reilly et al. may be utilised.

Long-term soccer-specific training enhances the rate of physical development of academy soccer players independent of maturation status.

The aim of the study was to compare 3-year changes in physical performance between junior soccer players selected for an elite academy and age-matched controls. The 3-year changes in indicators of the physical performance were quantified in 12-16-year-old Premier League Academy (n=27) and non-academy soccer players (n=18). Data were analysed with an age-group×competitive level general linear model, covariate-adjusted for initial performance level and change in maturation. Covariate adjusted mean±SD changes were greater (standardised effect size>0.7) for the academy players in terms of countermovement jump (7.3±2.6 vs. 5.4±2.5 cm), 10 m sprint (- 0.15±0.05 vs. - 0.10±0.04 s), 20 m sprint (- 0.30±0.16 s vs. - 0.15±0.13 s), agility (- 0.19±0.01 s vs. - 0.08±0.08 s), repeated sprint (- 0.60±0.26 s vs. - 0.41±2.1 s) and intermittent endurance capacity (1 128±406 vs. 315±370 m). These data indicate that a 3-year programme of training in an elite soccer academy is associated with greater changes in physical performance indicators independently from the initial performance level of the child and change in maturation over the same period of time.

A meta-analytic approach to quantify the dose-response relationship between melatonin and core temperature.

A melatonin-mediated reduction in body temperature could be useful as a "pre-cooling" intervention for athletes, as long as the melatonin dose is optimised so that substantial soporific effects are not induced. However, the melatonin-temperature dose-response relationship is unclear in humans. Individual studies have involved small samples of different sexes and temperature measurement sites. Therefore, we meta-analysed the effects of exogenous melatonin on body core temperature to quantify the dose-response relationship and to explore the influence of moderating variables such as sex and measurement site. Following a literature search, we meta-analysed 30 data-sets involving 193 participants and 405 ingestions of melatonin. The outcome was the mean difference (95 % confidence limits) in core temperature between the melatonin and placebo-controlled conditions in each study, weighted by the reciprocal of each standard error of the difference. The mean (95 % confidence interval) pooled reduction in core temperature was found to be 0.21 °C (0.18-0.24 °C). The dose-response relationship was found to be logarithmic (P < 0.0001). Doses of 0-5 mg reduced temperature by ~0.00-0.22 °C. Any further reductions in temperature were negligible with doses >5 mg. The pooled mean reduction was 0.13 °C (0.05-0.20 °C) for oral temperature vs 0.26 °C (0.20-0.32 °C) for tympanic and 0.22 °C (0.19-0.25 °C) for rectal temperature. In conclusion, our meta-regression revealed a logarithmic dose-response relationship between melatonin and its temperature lowering effects. A 5-mg dose of melatonin lowered core temperature by ~0.2 °C. Higher doses do not substantially increase this hypothermic effect and may induce greater soporific effects.

Taekwondo exercise protocols do not recreate the physiological responses of championship combat.

The aim of this study was to determine the external validity of Taekwondo-specific exercise protocols. 10 male international Taekwondo competitors (age 18±2 years) took part in a championship combat and an exercise protocol that simulated the activity pattern of Taekwondo combat. Heart rate and venous blood samples were obtained in both settings. Despite similarity in the activity profiles, the championship Taekwondo combats elicited higher (p<0.05) heart rate (188±8 beats.min - 1), plasma lactate (12.2±4.6 mmol.L - 1), glucose (10.3±1.1 mmol.L - 1), -glycerol (143.4±49.4 µmol.L - 1), -adrena-line (2.7±1.7 nmol.L - 1) and noradrenaline (14.3±9.4 nmol.L - 1) responses than the -Taekwondo exercise protocol (heart rate: 172±4 beats.min - 1; plasma lactate: 3.6±2.7 mmol.L - 1; glucose: 5.9±0.8 mmol.L - 1; glycerol: 77.7±21.3 µmol.L - 1; adrenaline: 0.6±0.2 nmol.L - 1 and noradrenaline: 3.0±1.1 nmol.L - 1). This discrepancy in the physiological responses appeared to be mediated by a reduced stress response in the Taekwondo exercise protocol. These findings suggest that Taekwondo-specific exercise protocols are not appropriate to study the physiological demands of Taekwondo. -Strategies designed to increase the stress response in this setting may be necessary to improve the external validity of this experimental framework.

Markers of bone health, renal function, liver function, anthropometry and perception of mood: a comparison between Flat and National Hunt Jockeys.

Given the requirement of professional jockeys to make-weight daily, we tested the hypothesis that Flat and National Hunt (Jump) jockeys would display compromised health markers (bone health, vitamin D, liver and kidney function and mood) compared with established clinical norms, with Flat jockeys affected the greater. Daily energy intake was lower in Flat compared with Jump jockeys (6.11±1.25 vs. 7.47±0.83 MJ.day - 1, P=0.01) whereas there was no difference in urine osmolality (811±198 vs. 678±317 mOsmol x kg(-1) respectively, P=0.13). Serum total 25(OH)D was insufficient in Flat and Jump jockeys (37.6±28 vs. 35.1±14 nmol x L(-1) respectively although there was no difference between groups (P=0.79). Markers of bone metabolism (Plasma ß-carboxy-terminal cross-linked teleopeptide (CTX) and Intact Parathyroid Hormone (PTH) and liver and kidney function were within clinical normative ranges although CTX and PTH were higher than average. Abnormal mood profiles were observed in both groups although significantly poorer in the Flat jockeys (P=0.01). We conclude that the current practices of jockeys to make-weight may have detrimental effects upon their health with Flat jockeys affected more so than Jump jockeys. Future studies should investigate the effects of improved dietary practices on the mental and physical health of Flat and Jump jockeys.

Science and football: evaluating the influence of science on performance.

The scientific study of football has its origins in the early research completed in the 1970's. Since these early efforts the available scientific knowledge base related to football has developed substantially. The ability of this scientific information to influence practice in the day-to-day activity of football organisations, especially elite teams, has been largely taken for granted. The close examination of this impact can lead to more uncertainty regarding the usefulness of the scientific data to the sport. Few articles are available that have attempted to critique the link between science and football practice. As such, the aims of this article are 2-fold; (i) to examine the historical background to "science and football" and to analyse the influence of sports science research on the current practice of coaches and practitioners within the sport and (ii) to identify potential ways to increase the influence of scientific research on practice in the "real world".

Variation of activity demands in small-sided soccer games.

The aim of the present study was to examine the physical and technical activity during different periods within small-sided soccer games (SSGs). 20 elite players completed 3 different SSGs (2-a-side, 3-a-side and 4-a-side games) in which the number of ball touches per individual possession was fixed at a maximum of 2. The duration and the pitch size of each SSG were strictly controlled (2 min, 3 min, 4 min, respectively; 1:75 m2) with each period repeated 4 times (P1, P2, P3, P4). The physical and technical activities, heart rate responses, blood lactate concentration and rating of perceived exertion (RPE) were analysed. The results showed a decrease of high and very high-intensity activities (from - 26.2% to - 37.7%, P<0.001), an increase of blood lactate concentration (from + 28.0% to + 76.9%), RPE (from + 29.0% to + 32.8%), and heart rate responses (~ 6.6%), and a significant alteration of technical activities from P1 to P4 in each SSG. The greatest differences from P1 and P4 were observed for the 2-a-side game when compared to the 3-a-side and 4-a-side games (P<0.05) for each variable analysed . In conclusion, the variation of the player's activity throughout the periods indicates that the duration and number of exercise periods used within SSGs is an important variable in determining the training stimulus in soccer-specific training.

A new tool to measure training load in soccer training and match play.

An accurate evaluation of training load is paramount for the planning and periodization of training. The aim of the present study was to evaluate the relationship between a new method to monitor training load in soccer (Visual Analogic Scale training load; VAS-TL), and two established heart rate-based methods (TRIMP and Edwards' method). 51 soccer players (age 15.6±0.3 years) answered 2 questions to assess perceived exertion and fatigue (VAS1-TL, and VAS2-TL) after training sessions and official matches. Performance in the Yo-Yo tests, VAS scores and heart rate of training sessions and matches, and match activity were analysed. We found significant correlations (r=0.60-0.72; p<0.05) between VAS-TL, TRIMP, and the Edwards' training load method, with the highest correlations achieved in the matches. Although the different methods to monitor training load were correlated with the distance covered during the match (r=0.53-0.78; p<0.05), only VAS1-TL was associated with high-intensity activities (r=0.43-0.54; p<0.05). The new VAS-based perceived exertion method to monitor training load is easy to apply and is sensitive to differences in positional role and physical capacity. Thus, the applied method may be used in addition to the usual training load methods, allowing for daily quantification of individual training load in soccer.

Circadian variation and soccer performance: implications for training and match-play during Ramadan.

Ramadan results in a number of behavioural alterations in individuals when compared to their normal habits outside of this holy month. These changes in behaviour could impact upon the effectiveness of the activity of an elite athlete who has high daily activity levels and energy expenditures. Understanding the true impact of Ramadan on human physiology will also require an awareness of the key aspects of circadian rhythms. This article will present theoretical background content on circadian rhythms along with data on the potential influence of circadian variation on soccer performance. It will also attempt to provide an insight into the problems of partial sleep deprivation and travel for the elite player. The contents will suggest that there is a basis for the within-day variation in physiological and psychological function to impact soccer performance if games are played early in the day or very late at night. As competitive fixtures are uncommon at these times these influences may be more relevant to the timing and organisation of training sessions. It is also likely that a lack of sleep and excessive travel will provide conditions that are not conducive to optimal performance. This would indicate that teams should think carefully about their preparation strategies for important tournaments and games.

The ingestion of combined carbohydrates does not alter metabolic responses or performance capacity during soccer-specific exercise in the heat compared to ingestion of a single carbohydrate.

This study was designed to investigate the effect of ingesting a glucose plus fructose solution on the metabolic responses to soccer-specific exercise in the heat and the impact on subsequent exercise capacity. Eleven male soccer players performed a 90 min soccer-specific protocol on three occasions. Either 3 ml · kg(-1) body mass of a solution containing glucose (1 g · min(-1) glucose) (GLU), or glucose (0.66 g · min(-1)) plus fructose (0.33 g · min(-1)) (MIX) or placebo (PLA) was consumed every 15 minutes. Respiratory measures were undertaken at 15-min intervals, blood samples were drawn at rest, half-time and on completion of the protocol, and muscle glycogen concentration was assessed pre- and post-exercise. Following the soccer-specific protocol the Cunningham and Faulkner test was performed. No significant differences in post-exercise muscle glycogen concentration (PLA, 62.99 ± 8.39 mmol · kg wet weight(-1); GLU 68.62 ± 2.70; mmol · kg wet weight(-1) and MIX 76.63 ± 6.92 mmol · kg wet weight(-1)) or exercise capacity (PLA, 73.62 ± 8.61 s; GLU, 77.11 ± 7.17 s; MIX, 83.04 ± 9.65 s) were observed between treatments (P > 0.05). However, total carbohydrate oxidation was significantly increased during MIX compared with PLA (P < 0.05). These results suggest that when ingested in moderate amounts, the type of carbohydrate does not influence metabolism during soccer-specific intermittent exercise or affect performance capacity after exercise in the heat.

An alternate dietary strategy to make weight improves mood, decreases body fat and removes the necessity for dehydration: A case-study from a professional jockey.

Professional jockeys are unique amongst weight-making athletes as they are often required to make weight daily and in many cases, all year round. Common methods employed by jockeys include dehydration, severe calorie restriction and sporadic eating, all of which have adverse health effects. In contrast, this paper outlines a structured diet and exercise plan employed by a 22 year old professional National Hunt jockey in an attempt to reduce weight from 70.3 to 62.6 kg that does not rely on any of the aforementioned techniques. Prior to the intervention, the client's typical daily energy intake was 8.2 MJ (42% CHO, 36% fats, 22% protein) consumed in two meals only. During the 9-week intervention, daily energy intake was approximately equivalent to resting metabolic rate and consumed as 6 meals per day (7.6 MJ, 46% CHO, 19% fats, 36% protein). This change in frequency and composition of energy intake combined with structured exercise, resulted in a total body mass loss of 8 kg, corresponding to reductions in percent body fat from 14.5 to 9%. No form of intentional dehydration occurred throughout this period and mean urine osmolality was 285 mOs·kg-1 (SD 115 mOs·kg-1). In addition, positive changes in mood scores (BRUMS scale) also occurred. The client was now able to ride light for the first time in his career thereby challenging the cultural practices inherent to the sport.

Sport-specific fitness testing differentiates professional from amateur soccer players where VO2max and VO2 kinetics do not.

AIM: The purpose of this study was to identify if sport-specific and cardiopulmonary exercise testing differentiated professional from amateur soccer players. METHODS: Thirty six men comprising 18 professional (mean±s: age 23.2±2.4 years) and 18 amateur (mean±SD: age 21.1±1.6 years) soccer players participated and performed four tests on separate occasions: 1) a graded exercise test to determine VO2max; 2) four exercise transients from walking to 80%Δ for the determination of VO2 kinetics; 3) the Yo-Yo Intermittent Recovery Test level 2 (Yo-Yo IR2) and 4) a repeated sprint test (RST). RESULTS: The players did not differ in VO2max (professional 56.5±2.9 mL.kg-1.min-1; amateur 55.7±3.5 mL.kg-1.min-1: P=0.484) or VO2 kinetic fundamental measures (τ1 onset, professional 24.5±3.2 s; amateur 24.0±1.8 s: τ1 cessation, professional 28.7±2.8 s; amateur 29.3±3.5 s: P=0.923). However, the amateurs were outperformed in the Yo-Yo IR2 (Professional 966±153 m; Amateur 840±156 m) (P=0.034) and RST (best time, professional 6.46±0.27 s; amateur 6.84±0.24 s, P=0.012). CONCLUSION: Performance indices derived from field-based sport-specific performance tests identified significant differences between professional and amateur players (P<0.05). However, neither tests of VO2 kinetics nor VO2max differentiated between groups, suggesting laboratory tests of cardiorespiratory parameters are probably less consequential to soccer than sport-specific field-based observations.

Carbohydrate ingestion and pre-cooling improves exercise capacity following soccer-specific intermittent exercise performed in the heat.

Ingestion of carbohydrate and reducing core body temperature pre-exercise, either separately or combined, may have ergogenic effects during prolonged intermittent exercise in hot conditions. The aim of this investigation was to examine the effect of carbohydrate ingestion and pre-cooling on the physiological responses to soccer-specific intermittent exercise and the impact on subsequent high-intensity exercise performance in the heat. Twelve male soccer players performed a soccer-specific intermittent protocol for 90 min in the heat (30.5°C and 42.2% r.h.) on four occasions. On two occasions, the participants underwent a pre-cooling manoeuvre. During these sessions either a carbohydrate-electrolyte solution (CHOc) or a placebo was consumed at (PLAc). During the remaining sessions either the carbohydrate-electrolyte solution (CHO) or placebo (PLA) was consumed. At 15-min intervals throughout the protocol participants performed a mental concentration test. Following the soccer-specific protocol participants performed a self-chosen pace test and a test of high-intensity exercise capacity. The period of pre-cooling significantly reduced core temperature, muscle temperature and thermal sensation (P < 0.05). Self-chosen pace was greater with CHOc (12.5 ± 0.5 km h(-1)) compared with CHO (11.3 ± 0.4 km h(-1)), PLA (11.3 ± 0.4 km h(-1)) and PLAc (11.6 ± 0.5 km h(-1)) (P < 0.05). High-intensity exercise capacity was improved with CHOc and CHO when compared with PLA (CHOc; 79.8 ± 7 s, CHO; 72.1 ± 5 s, PLAc; 70.1 ± 8 s, PLA; 57.1 ± 5 s; P < 0.05). Mental concentration during the protocol was also enhanced during CHOc compared with PLA (P < 0.05). These results suggest pre-cooling in conjunction with the ingestion of carbohydrate during exercise enhances exercise capacity and helps maintain mental performance during intermittent exercise in hot conditions.

Diurnal variation in the salivary melatonin responses to exercise: relation to exercise-mediated tachycardia.

Salivary melatonin concentration is an established marker of human circadian rhythmicity. It is thought that melatonin is relatively robust to the masking effects of exercise. Nevertheless, the extent and even the direction of exercise-related change is unclear, possibly due to between-study differences in the time of day exercise is completed. Therefore, we aimed to compare melatonin responses between morning and afternoon exercise, and explore the relationships between exercise-related changes in melatonin and heart rate. At 08:00 and 17:00 hours, seven male subjects (mean ± SD age, 27 ± 5 years) completed 30 min of cycling at 70% peak oxygen uptake followed by 30 min of rest. Light intensity was maintained at ~150 lx. Salivary melatonin (ELISA) and heart rate were measured at baseline, 15 min during exercise, immediately post-exercise and following 30 min recovery. Melatonin was ≈15 pg ml(-1) higher in the morning trials compared with the afternoon (P = 0.030). The exercise-related increase in melatonin was more pronounced (P = 0.024) in the morning (11.1 ± 8.7 pg ml(-1)) than in the afternoon (5.1 ± 5.7 pg ml(-1)). The slope of the heart rate-melatonin relationship was significantly (P = 0.020) steeper in the morning (0.12 pg ml(-1) beats(-1 )min(-1)) than in the afternoon (0.03 pg ml(-1) beats(-1 )min(-1)). In conclusion, we report for the first time that the masking effect of moderate-intensity exercise on melatonin is approximately twice as high in the morning than the afternoon. The much steeper relationship between heart rate and melatonin changes in the morning raises the possibility that time of day alters the relationships between exercise-mediated sympathetic nervous activity and melatonin secretion.