Auditing the Representation of Females Versus Males in Heat Adaptation Research.

The aim of this audit was to quantify female representation in research on heat adaptation. Using a standardized audit tool, the PubMed database was searched for heat adaptation literature from inception to February 2023. Studies were included if they investigated heat adaptation among female and male adults (≥18-50 years) who were free from noncommunicable diseases, with heat adaptation the primary or secondary outcome of interest. The number and sex of participants, athletic caliber, menstrual status, research theme, journal impact factor, Altmetric score, Field-Weighted Citation Impact, and type of heat exposure were extracted. A total of 477 studies were identified in this audit, including 7,707 participants with ∼13% of these being female. Most studies investigated male-only cohorts (∼74%, n = 5,672 males), with ∼5% (n = 360 females) including female-only cohorts. Of the 126 studies that included females, only 10% provided some evidence of appropriate methodological control to account for ovarian hormone status, with no study meeting best-practice recommendations. Of the included female participants, 40% were able to be classified to an athletic caliber, with 67% of these being allocated to Tier 2 (i.e., trained/developmental) or below. Exercise heat acclimation was the dominant method of heat exposure (437 interventions), with 21 studies investigating sex differences in exercise heat acclimation interventions. We recommend that future research on heat adaptation in female participants use methodological approaches that consider the potential impact of sexual dimorphism on study outcomes to provide evidence-based guidelines for female athletes preparing for exercise or competition in hot conditions.

Validity of the PUSH band 2.0 and Speed4lifts to measure velocity during upper and lower body free-weight resistance exercises.

Accuracy and test-retest reliability were assessed for two devices, PUSH Band 2.0 (PUSH) and Speed4lifts. Two identical sessions were performed 6-8 days apart. Twenty rugby league players performed three repetitions with 20%, 40%, 60% and 80% of estimated one repetition maximum for back squat (BS), front squat (FS), and bench press (BP). Velocity was recorded using PUSH, Speed4lifts and 3D motion analysis system (gold standard). Passing-Bablok regression analysis assessed agreement of velocity measures with the gold standard. Intraclass correlation coefficients (ICC) and coefficients of variation (CV) assessed test-retest reliability. PUSH and Speed4lifts were accurate for BS velocities <1.00 m/s and FS velocities <0.65 m/s. PUSH was accurate for BP velocities <0.65 m/s. Speed4lifts was accurate for BP velocities between 0.65-1.00 m/s. PUSH was reliable at all loads (ICC = 0.79-0.92; CV = 2.63-6.89%) except for 20% FS and BP (ICC = 0.49-0.64; CV = 3.13-3.62%). Speed4lifts was reliable at all loads (ICC = 0.70-0.96; CV = 2.57-4.26%) except for 20% BP (ICC = 0.59; CV = 4.59%). These results suggest that both devices are unsuitable for measuring the velocity of BS, FS and BP at faster velocities and at lighter loads.

"If they can do it, I can do it": experiences of older women who engage in powerlifting training.

Older adults' participation in resistance training is low. Recent research suggests social aspects are important determinants of exercise engagement. In this study, 13 older women (50 years and older) were interviewed to examine their experiences of powerlifting training. Data were thematically analyzed revealing two main themes: Challenging Beliefs and Positive Social Influences. Peer advocates were essential for uptake, with social interactions in group resistance training, and having a skilled trainer, identified as important adherence factors. Strategies to improve resistance training uptake in older women could leverage off the experience of others and powerlifting training culture and practices.

Measuring Decrement in Change-of-Direction Speed Across Repeated Sprints in Basketball: Novel vs. Traditional Approaches.

ABSTRACT: Scanlan, AT, Madueno, MC, Guy, JH, Giamarelos, K, Spiteri, T, and Dalbo, VJ. Measuring decrement in change-of-direction speed across repeated sprints in basketball: Novel vs. traditional approaches. J Strength Cond Res 35(3): 841-845, 2021-Approaches to quantify decrement in change-of-direction speed during repeated sprints in basketball players have traditionally used total performance time, which is strongly influenced by linear speed. The purpose of this study was to compare performance decrement across change-of-direction sprints using total performance time and a novel approach that better isolates change-of-direction speed, termed change-of-direction deficit (CODD). Semiprofessional basketball players (N = 8; 19.9 ± 1.5 years; 183.0 ± 9.6 cm; 77.7 ± 16.9 kg) completed 12 × 20-m change-of-direction sprints (Agility 5-0-5 trials) with 20-second recoveries between each sprint. Agility 5-0-5 performance time was taken as the duration to cover 5 m immediately before and after (10 m in total) a 180° directional change. Change-of-direction deficit was calculated as the difference between mean 10- and 20-m split time determined during reference 20-m linear sprints in a separate session and Agility 5-0-5 time in each sprint. Performance decrement was calculated for each approach as: ([total time/ideal time] × 100) - 100. Comparisons between approaches were made using a paired-sample t-test, effect size analyses, and magnitude-based inferences. A significantly greater (P < 0.001; effect size = 2.16, very large; almost certainly higher) performance decrement was apparent using CODD (5.99 ± 1.88%) than Agility 5-0-5 performance time (2.84 ± 0.84%). The present findings indicate that change-of-direction speed measured with CODD shows promise in providing different insight and deteriorates more than total performance time during repeated sprints in basketball players. Change-of-direction deficit has potential to better isolate decrements in change-of-direction speed across repeated sprints compared with total performance time.

Validity and Reliability of Using Load-Velocity Relationship Profiles to Establish Back Squat 1 m·s-1 Load.

ABSTRACT: Elsworthy, N, Callaghan, DE, Scanlan, AT, Kertesz, AHM, Kean, CO, Dascombe, BJ, and Guy, JH. Validity and reliability of using load-velocity relationship profiles to establish back squat 1 m·s-1 load. J Strength Cond Res 35(2): 340-346, 2021-Although measuring movement velocity during resistance exercise is being increasingly used to monitor player readiness for competition in team sports, the validity and reliability of using set target velocities has not been examined. This study examined test-retest reliability of the load-velocity relationship during the back squat to predict loads corresponding to a mean velocity of 1 m·s-1 (V1Load), test-retest reliability of mean concentric velocity at V1Load, and criterion validity of mean concentric velocity at V1Load. Twenty-seven resistance-trained male rugby league players completed 2 testing sessions on separate days to establish individualized back squat load-velocity relationship profiles (30, 40, 60, and 80% estimated 1 repetition maximum). Velocity during the back squat was assessed at each load and V1Load derived using individualized linear regression equations. A subset of subjects (n = 18) also performed the back squat at predicted V1Load to examine the test-retest reliability and compare the mean concentric velocity with the predicted target of 1 m·s-1. The mean concentric velocity was consistent across all loads during load-velocity relationship testing (p > 0.05, intraclass correlation coefficient [ICC] ≥0.75, coefficient of variation [CV] ≤5.7%, effect size [ES] ≤0.27), and for predicting V1Load (p = 0.11, ICC = 0.95, CV = 3.9%, ES = 0.11). The mean concentric velocity at V1Load was reliable (ICC = 0.77; CV = 2.6%; ES = 0.39) and not significantly different (p = 0.21) to the target velocity, supporting criterion validity. Individualized load-velocity profiles for the back squat can accurately predict V1Load, and subsequent use of V1Load to assess back squat velocity is valid and reliable. Using V1Load to assess changes in back squat velocity may have application in measuring changes in strength and power or readiness to train.

Dribble Deficit: A novel method to measure dribbling speed independent of sprinting speed in basketball players.

Basketball tests assessing dribbling speed predicated on total performance times are influenced by sprinting speed. This study examines an approach termed Dribble Deficit to counter this limitation by examining the relationships between sprinting and dribbling speed during linear and change-of-direction (COD) tasks measured using total performance time and Dribble Deficit. Ten semi-professional basketball players completed linear sprints and COD sprints with and without dribbling. Dribble Deficit was calculated as the difference between the best time for each dribbling trial and corresponding non-dribbling trial for linear and COD sprints. Large to very large significant relationships (P < 0.05) were evident between linear sprint and dribble times (R = 0.64-0.77, R2 = 0.41-0.59), and between COD sprint and dribble times (R = 0.88, R2 = 0.77). Conversely, trivial-small relationships were evident between linear sprint time and linear Dribble Deficit (R = 0.01-0.15, R2 = 0.00-0.02). A non-significant, moderate, negative relationship was observed between COD sprint time and COD Dribble Deficit (R = -0.45, R2 = 0.20). These findings indicate Dribble Deficit provides a more isolated measure of dribbling speed than tests using total performance times. Basketball practitioners may use Dribble Deficit to measure dribbling speed independent of sprint speed in test batteries.

Short-term reliability of inflammatory mediators and response to exercise in the heat.

Prospective application of serum cytokines, lipopolysaccharide (LPS), and heat shock proteins (eHSPs) requires reliable measurement of these biomarkers that can signify exercise-induced heat stress in hot conditions. To accomplish this, both short-term (7 day) reliability (at rest, n = 12) and the acute responsiveness of each biomarker to exercise in the heat (pre and post 60-min cycling, 34.5°C and 70% RH, n = 20) were evaluated. Serum was analysed for the concentration of C-reactive protein (CRP), interleukin-6 (IL-6), heat shock protein 72 (eHSP72), immunoglobulin M (IgM) and LPS. Test-retest reliability was determined as the coefficient of variation (CV). Biomarkers with the least short-term within-participant variation were IL-6 (19%, ±20%; CV, ±95% confidence limits (CL)) and LPS (23%, ±13%). Greater variability was observed for IgM, eHSP72 and CRP (CV range 28-38%). IL-6 exhibited the largest increase in response to acute exercise (95%, ±11%, P = < 0.001) and although CRP had a modest CV (12%, ±7%), it increased substantially post-exercise (P = 0.02, ES; 0.78). In contrast, eHSP72 and LPS exhibited trivial changes post-exercise. It appears variation of common inflammatory markers after exercise in the heat is not always discernible from short-term (weekly) variation.

Immune and inflammatory responses of Australian firefighters after repeated exposures to the heat.

When firefighters work in hot conditions, altered immune and inflammatory responses may increase the risk of a cardiac event. The present study aimed to establish the time course of such responses. Forty-two urban firefighters completed a repeat work protocol in a heat chamber (100 ± 5°C). Changes to leukocytes, platelets, TNFα, IL-6, IL-10, LPS and CRP were evaluated immediately post-work and also after 1 and 24 h of rest. Increases in core temperatures were associated with significant increases in leukocytes, platelets and TNFα directly following work. Further, platelets continued to increase at 1 h (+31.2 ± 31.3 × 10(9) l, p < 0.01) and remained elevated at 24 h (+15.9 ± 19.6 × 10(9) l, p < 0.01). Sustained increases in leukocytes and platelets may increase the risk of cardiac events in firefighters when performing repeat work tasks in the heat. This is particularly relevant during multi-day deployments following natural disasters. Practitioner Summary: Firefighters regularly re-enter fire affected buildings or are redeployed to further operational tasks. Should work in the heat lead to sustained immune and inflammatory changes following extended rest periods, incident controllers should plan appropriate work/rest cycles to minimise these changes and any subsequent risks of cardiac events.

Inspiratory muscle training improves exercise tolerance in recreational soccer players without concomitant gain in soccer-specific fitness.

This study investigated whether the addition of inspiratory muscle training (IMT) to an existing program of preseason soccer training would augment performance indices such as exercise tolerance and sports-specific performance beyond the use of preseason training alone. Thirty-one men were randomized across 3 groups: experimental (EXP: n = 12), placebo (PLA: n = 9), and control (CON: n = 10). The EXP and PLA completed a 6-week preseason program (2× weekly sessions) in addition to concurrent IMT with either an IMT load (EXP) or negligible (PLA) inspiratory resistance. Control group did not use an IMT device or undertake soccer training. All participants performed the following tests before and after the 6-week period: standard spirometry; maximal inspiratory mouth pressure (MIP); multistage fitness test (MSFT); and a soccer-specific fitness test (SSFT). After 6-weeks training, EXP significantly improved: MIP (p = 0.002); MSFT distance covered (p = 0.02); and post-SSFT blood lactate (BLa) (p = 0.04). No other outcomes from the SSFT were changed. Pre- to posttraining performance outcomes for PLA and CON were unchanged. These findings suggest the addition of IMT to preseason soccer training improved exercise tolerance (MSFT distance covered) but had little effect on soccer-specific fitness indices beyond a slightly reduced posttraining SSFT BLa. In conclusion, there may be benefit for soccer players to incorporate IMT to their preseason training but the effect is not conclusive. It is likely that a greater preseason training stimulus would be particularly meaningful for this population if fitness gains are a priority and evoke a stronger IMT response.

Isokinetic Shoulder Strength and its Associations to Injury in Tactical Populations: A Critical Review.

The aim of this review is to evaluate existing isokinetic testing protocols for the shoulder in tactical occupations, document their shoulder strength profiles, and determine any associations to shoulder injury. Four electronic databases were searched (Medline/Pubmed, Ovid/Emcare, CINAHL/Ebsco and Embase) using the keywords police OR law enforcement, firefighter, military, AND isokinetic. Articles were eligible if they had at least one cohort of a tactical population and included isokinetic testing of the glenohumeral joint. The search yielded 275 articles. After screening for duplicates and inclusion criteria, 19 articles remained for review, six of which assessed injury correlation. 17 articles evaluated military personnel and two examined firefighters. Articles were categorized by study design, population, isokinetic protocols, strength outcome measures and statistical measures. Concentric internal rotation (IR) and external rotation (ER) strength at 60 degrees/second were reported most frequently (84% of cases). There was a paucity of testing speeds, repetition ranges and contraction types evaluated when compared to existing literature in other populations with high shoulder injury occurrence such as overhead and collision athletes. Outside of military cohorts, there is limited data available to characterise the isokinetic strength profile of the shoulder in tactical occupations. Meta-analysis for injury association was unable to be performed due to independent variable and statistical heterogeneity. However, a best evidence synthesis suggested conflicting evidence to support the association of injury with isokinetic strength testing in tactical populations. Future studies should prioritise prospective designs utilising variable speeds, repetition schemes and contraction types to better capture the dynamic occupational demands in tactical groups.

Heat Adaptation for Females: A Systematic Review and Meta-Analysis of Physiological Adaptations and Exercise Performance in the Heat.

BACKGROUND: Heat adaptation regimes are used to prepare athletes for exercise in hot conditions to limit a decrement in exercise performance. However, the heat adaptation literature mostly focuses on males, and consequently, current heat adaptation guidelines may not be optimal for females when accounting for the biological and phenotypical differences between sexes. OBJECTIVES: We aimed to examine: (1) the effects of heat adaptation on physiological adaptations in females; (2) the impact of heat adaptation on performance test outcomes in the heat; and (3) the impact of various moderators, including duration (minutes and/or days), total heat dose (°C.min), exercise intensity (kcal.min-1), total energy expended (kcal), frequency of heat exposures and training status on the physiological adaptations in the heat. METHODS: SPORTDiscus, MEDLINE Complete and Embase databases were searched to December 2022. Random-effects meta-analyses for resting and exercise core temperature, skin temperature, heart rate, sweat rate, plasma volume and performance tests in the heat were completed using Stata Statistical Software: Release 17. Sub-group meta-analyses were performed to explore the effect of duration, total heat dose, exercise intensity, total energy expended, frequency of heat exposure and training status on resting and exercise core temperature, skin temperature, heart rate and sweat rate. An explorative meta-regression was conducted to determine the effects of physiological adaptations on performance test outcomes in the heat following heat adaptation. RESULTS: Thirty studies were included in the systematic review; 22 studies were meta-analysed. After heat adaptation, a reduction in resting core temperature (effect size [ES] = - 0.45; 95% confidence interval [CI] - 0.69, - 0.22; p < 0.001), exercise core temperature (ES = - 0.81; 95% CI - 1.01, - 0.60; p < 0.001), skin temperature (ES = - 0.64; 95% CI - 0.79, - 0.48; p < 0.001), heart rate (ES = - 0.60; 95% CI - 0.74, - 0.45; p < 0.001) and an increase in sweat rate (ES = 0.53; 95% CI 0.21, 0.85; p = 0.001) were identified in females. There was no change in plasma volume (ES = - 0.03; 95% CI - 0.31, 0.25; p = 0.835), whilst performance test outcomes were improved following heat adaptation (ES = 1.00; 95% CI 0.56, 1.45; p < 0.001). Across all moderators, physiological adaptations were more consistently observed following durations of 451-900 min and/or 8-14 days, exercise intensity ≥ 3.5 kcal.min-1, total energy expended ≥ 3038 kcal, consecutive (daily) frequency and total heat dose ≥ 23,000 °C.min. The magnitude of change in performance test outcomes in the heat was associated with a reduction in heart rate following heat adaptation (standardised mean difference = - 10 beats.min-1; 95% CI - 19, - 1; p = 0.031). CONCLUSIONS: Heat adaptation regimes induce physiological adaptations beneficial to thermoregulation and performance test outcomes in the heat in females. Sport coaches and applied sport practitioners can utilise the framework developed in this review to design and implement heat adaptation strategies for females.

Player chronotype does not affect shooting accuracy at different times of the day in a professional, male basketball team: a pilot study.

Athlete chronotype has been documented to underpin diurnal variations in skill execution across various team sports. However, no research has explored the effects of athlete chronotype on basketball-specific skills at different times of the day. Therefore, the aim of this study was to explore diurnal variations in basketball shooting accuracy according to chronotype. Professional, male basketball players (n = 13) completed a Morningness- Eveningness Questionnaire and were categorised into chronotypes using a tertile split technique (morning-types: n = 4; neither-types: n = 4; evening-types: n = 5). Players completed separate trials of a shooting accuracy test in the morning (08:00-09:30h) and afternoon (15:00-16:30h) with each trial consisting of 20 shots attempted from four court locations at either two- or three-point distances and one-shot location from the free-throw line (100 shots in total). Each shot attempt was scored using a 0-3-point scale with higher scores awarded to more accurate shots. Non-significant (p >0.05) differences in shooting scores were evident between morning and afternoon trials for each chronotype group, with small-large effects in shooting scores favouring the morning across groups. Moreover, non-significant (p >0.05) differences in shooting scores were apparent between chronotype groups in the morning (small-large effects) and afternoon (moderate-large effects). Shooting accuracy appears to remain consistent across morning and afternoon performances irrespective of player chronotype in a professional basketball team, suggesting coaches may not need to schedule training sessions involving shooting tasks at specific times of the day to optimise shooting accuracy in players.

Competing in Hot Conditions at the Tokyo Olympic Games: Preparation Strategies Used by Australian Race Walkers.

Introduction: The Tokyo 2021 Olympic Games was anticipated to expose athletes to the most challenging climatic conditions experienced in the history of the modern Olympic Games. This study documents strategies executed by Australian endurance athletes during the team holding camp and Olympic Games experiences, including (1) baseline physiological data, training data, and heat acclimation/acclimatization practices; (2) pre- and in-race cooling and nutritional strategies, and (3) Olympic Games race performance data. Methods: Six athletes (three males, three females; age 24 ± 4 years; VO2max 63.2 ± 8.7 mL⋅kg-1⋅min-1; sum of 7 skinfolds 53.1 ± 23.4 mm) were observed prior to and during the team holding camp held in Cairns, QLD, Australia. Athletes completed 6-7 weeks of intermittent heat acclimation training, utilizing a combination of 2-4 passive and active acclimation sessions per week. Active acclimation was systematically increased via exposure time, exercise intensity, temperature, and humidity. In the team holding camp, athletes undertook a further 23 heat acclimatization training sessions over 18 days in a continuous fashion. Hyperhydration (using sodium and glycerol osmolytes), and internal and external pre-and in-race cooling methods were also utilized. A low energy availability intervention was implemented with two athletes, as a strategy to periodize ideal race body composition. Race performance data and environmental conditions from the 2021 Olympic Games were also documented. Results: The highest values for aerobic capacity were 63.6 mL⋅kg-1⋅min-1 for female race walkers and 73.7 mL⋅kg-1⋅min-1 for males. Training volume for the six athletes was the highest in the second week of the team holding camp, and training intensity was lowest in the first week of the team holding camp. Performance outcomes included 6th place in the women's 20 km event (1:30:39), which was within 2% of her 20 km personal best time, and 8th place in the men's 50 km event (3:52:01), which was a personal best performance time. Conclusion: Periodized training, heat acclimation/acclimatization, cooling and nutritional strategies study may have contributed to the race outcomes in Olympic Games held hot, humid conditions, for the race walkers within this observational study.

A Comparison of PlayerLoadTM and Heart Rate during Backwards and Forwards Locomotion during Intermittent Exercise in Rugby League Players.

Limited research has examined the demands of backward locomotion at various speeds using common load monitoring metrics in team sport athletes. Consequently, this study compared the external and internal loads between backward and forward locomotion during intermittent exercise in team sport athletes. Semi-professional, male rugby league players (n = 29) completed the same exercise protocol on two occasions in backward and forward directions. On each occasion, participants performed separate 20 m trials at self-selected walking, jogging, running, and sprinting speeds and then completed a 15 min modified Loughborough intermittent shuttle test (mLIST). Common external and internal load metrics were gathered across testing. Faster speeds (p < 0.001) were attained at all speeds during forward locomotion in the 20 m trials. Non-significant differences in accumulated PlayerLoadTM were found between directions across the mLIST; however, higher relative (per min) PlayerLoadTM (p < 0.001) was apparent during backward locomotion when walking and during forward locomotion when sprinting during the mLIST. RPE and mean heart rate were higher (p < 0.001) during backward locomotion across the mLIST. These data highlight the unique loading patterns experienced during backward locomotion and suggest practitioners should consider the discernment in loading imposed between backward and forward locomotion when measuring athlete demands using common metrics.

Back squat velocity to assess neuromuscular status of rugby league players following a match.

OBJECTIVES: Back squat mean concentric velocity (MV) and countermovement jump (CMJ) performance were examined in sub-elite rugby league players post-match to monitor changes in neuromuscular status (NMS) from baseline. Relationships between changes in back squat MV and CMJ performance variables were used to compare back squat MV to an established method to monitor NMS. DESIGN: Longitudinal observational design. METHODS: 18 male sub-elite rugby league players (mean±SD, 20.5±2.4 yr; 180.0±6.7cm; 93.3±11.2kg) performed 3 repetitions of CMJ and back squat with an individualised, pre-determined load at -2h (baseline), +30min, +24h, and +48h in relation to a match. Back squat MV, CMJ height, CMJ peak power, and CMJ peak velocity were measured with a linear position transducer. RESULTS: Significant (p<0.05), small to large decreases (ES=0.52-1.24) were observed in back squat MV up to +48h post-match. Significant (p<0.05), small to moderate decreases (ES=0.52-0.70) in CMJ height were also observed up to +24h post-match, returning to baseline at +48h. CMJ peak power and peak velocity post-match changes were not significant compared to baseline (p>0.05). Significant positive correlations were found between changes in back squat MV and CMJ height at +30min (r=0.59; p=0.009) and +48h (r=0.51; p=0.03). CONCLUSIONS: These findings suggest back squat MV may be a suitable alternative or addition to CMJ testing for monitoring NMS in rugby league players.

The Isometric Midthigh Pull in Basketball: An Effective Predictor of Sprint and Jump Performance in Male, Adolescent Players.

PURPOSE: To examine correlations between peak force and impulse measures attained during the isometric midthigh pull (IMTP) and basketball-specific sprint and jump tests. METHODS: Male, adolescent basketball players (N = 24) completed a battery of basketball-specific performance tests. Testing consisted of the IMTP (absolute and normalized peak force and impulse at 100 and 250 ms); 20-m sprint (time across 5, 10, and 20 m); countermovement jump (CMJ; absolute and normalized peak force and jump height); standing long jump (distance); and repeated lateral bound (distance). Correlation and regression analyses were conducted between IMTP measures and other attributes. RESULTS: An almost perfect correlation was evident between absolute peak force attained during the IMTP and CMJ (r = .94, R2 = 56%, P < .05). Moderate to very large correlations (P < .05) were observed between IMTP normalized peak force and 5-m sprint time (r = -.44, R2 = 19%), 10-m sprint time (r = -.45, R2 = 20%), absolute (r = .57, R2 = 33%), normalized (r = .86, R2 = 73%) CMJ peak force, and standing long-jump distance (r = .51, R2 = 26%). Moderate to very large correlations were evident between impulse measures during the IMTP and 5-m sprint time (100 ms, r = -.40, R2 = 16%, P > .05) and CMJ absolute peak force (100 ms, r = .73, R2 = 54%; 250 ms, r = .68, R2 = 47%; P < .05). CONCLUSIONS: The IMTP may be used to assess maximal and rapid force expression important across a range of basketball-specific movements.

Hot, Tired and Hungry: The Snacking Behaviour and Food Cravings of Firefighters During Multi-Day Simulated Wildfire Suppression.

Firefighters are exposed to numerous stressors during wildfire suppression, including working in hot temperatures and sleep restricted conditions. Research has shown that when sleep restricted, individuals choose foods higher in carbohydrates, fat, and sugar, and have increased cravings for calorie dense foods. However, there is currently no research on the combined effect of heat and sleep restriction on snacking behaviour. Conducting secondary analyses from a larger study, the current study aimed to investigate the impact of heat and sleep restriction on snacking behaviour and food cravings. Sixty-six firefighters completed three days of simulated physically demanding firefighting work and were randomly allocated to either the control (n = 18, CON; 19 °C, 8h sleep opportunity), sleep restricted (n = 16, SR; 19 °C, 4-h sleep opportunity), hot (n = 18, HOT; 33 °C, 8h sleep opportunity), or hot and sleep restricted (n = 14 HOT + SR; 33 °C, 4-h sleep opportunity) condition. During rest periods firefighters were able to self-select sweet, savoury, or healthy snacks from a ration pack and were asked to rate their hunger, fullness, and cravings every two hours (eating block). Mixed model analyses revealed no difference in total energy intake between conditions, however there was a significant interaction between eating block and condition, with those in the CON, HOT, and HOT + SR condition consuming significantly more energy between 1230 and 1430 compared to the SR condition (p = 0.002). Sleep restriction and heat did not impact feelings of hunger and fullness across the day, and did not lead to greater cravings for snacks, with no differences between conditions. These findings suggest that under various simulated firefighting conditions, it is not the amount of food that differs but the timing of food intake, with those that are required to work in hot conditions while sleep restricted more likely to consume food between 1230 and 1430. This has potential implications for the time of day in which a greater amount of food should be available for firefighters.

A systematic review examining the physiological, perceptual, and performance effects of active and passive recovery modes applied between repeated-sprints.

INTRODUCTION: Repeated-sprinting involves performing frequent short sprints (≤10 s) interspersed with brief recovery periods (≤60 s). Studies involving repeated-sprint protocols have typically employed active or passive recovery modes applied between running and cycling sprints. This review synthesized the literature to determine the acute physiological, perceptual, and performance effects of recovery mode applied between repeated-sprints during running and cycling protocols. EVIDENCE ACQUISITION: A systematic search was conducted according to PRISMA guidelines. Articles were retrieved from PubMed, Scopus, SPORTDiscus, and MEDLINE databases. Studies were eligible if they: 1) compared active and passive recovery applied between repeated-sprints; 2) examined sprints lasting ≤10 s, and; 3) included ≤60 s recovery between sprints. Nine studies were included in this review. Five of the included studies examined running and four studies examined cycling. EVIDENCE SYNTHESIS: Passive recovery induced less physiological stress (heart rate, oxygen consumption, and changes in oxyhemoglobin), lower perceptual stress (rating of perceived exertion), and reduced performance decrement (sprint time, speed, and sprint decrement) compared to active recovery in all running studies. Findings were equivocal in cycling. CONCLUSIONS: Application of passive recovery between running repeated-sprints is recommended to reduce performance decrement than passive recovery. Alternatively, active recovery applied between running repeated-sprints provides greater physiological stress than passive recovery and may be a useful training overload strategy to promote physiological adaptation. The mixed findings for physiological and performance measures in cycling studies suggest further research is required to reach definitive conclusions regarding application of recovery modes between cycling repeated-sprints.

Nutrition and Supplementation Considerations to Limit Endotoxemia When Exercising in the Heat.

Exercise-induced heat production is further elevated by exercise performed in hot conditions and this can subsequently impact inflammation, and gastrointestinal (GI) health. Implementing nutrition and supplementation strategies under these conditions may support the hyperthermic response, the systemic inflammatory response, GI permeability and integrity, and exercise performance. Therefore, the aim of this brief review is to explore athletes' inflammatory response of two key biomarkers, lipopolysaccharide (LPS), and interleukin-6 (IL-6), and provide nutrition and supplementation recommendations when exercising in hot conditions. There is emerging evidence that probiotics, glutamine, and vitamin C can preserve GI integrity, which may improve performance during exercise in the heat. Glucose rich food when consumed with water, before and during exercise in the heat, also appear to limit endotoxemia, preserve GI integrity, and reduce the incidence of GI disturbances compared with water alone. The use of non-steroidal anti-inflammatory drugs (NSAIDs) may compromise GI integrity and this may result in greater leakage of endotoxins during long duration exercise in the heat. Further work is required to elucidate the impact of nutrition and supplementation strategies, in particular the use of NSAIDs, when exercising in the heat.

Reduced Fatigue in Passive Versus Active Recovery: An Examination of Repeated-Change-of-Direction Sprints in Basketball Players.

PURPOSE: To investigate the physiological and performance effects of active and passive recovery between repeated-change-of-direction sprints. METHODS: Eight semiprofessional basketball players (age: 19.9 [1.5] y; stature: 183.0 [9.6] cm; body mass: 77.7 [16.9] kg; body fat: 11.8% [6.3%]; and peak oxygen consumption: 46.1 [7.6] mL·kg-1·min-1) completed 12 × 20-m repeated-change-of-direction sprints (Agility 5-0-5 tests) interspersed with 20 seconds of active (50% maximal aerobic speed) or passive recovery in a randomized crossover design. Physiological and perceptual measures included heart rate, oxygen consumption, blood lactate concentration, and rating of perceived exertion. Change-of-direction speed was measured during each sprint using the change-of-direction deficit (CODD), with summed CODD time and CODD decrement calculated as performance measures. RESULTS: Average heart rate (7.3 [6.4] beats·min-1; P = .010; effect size (ES) = 1.09; very likely) and oxygen consumption (4.4 [5.0] mL·kg-1·min-1; P = .12; ES = 0.77; unclear) were moderately greater with active recovery compared with passive recovery across sprints. Summed CODD time (0.87 [1.01] s; P = .07; ES = 0.76, moderate; likely) and CODD decrement (8.1% [3.7%]; P < .01; ES = 1.94, large; almost certainly) were higher with active compared with passive recovery. Trivial-small differences were evident for rating of perceived exertion (P = .516; ES = 0.19; unclear) and posttest blood lactate concentration (P = .29; ES = 0.40; unclear) between recovery modes. CONCLUSIONS: Passive recovery between repeated-change-of-direction sprints may reduce the physiological stress and fatigue encountered compared with active recovery in basketball players.