Meta-analysis prediction intervals are under reported in sport and exercise medicine.

AIM: Prediction intervals are a useful measure of uncertainty for meta-analyses that capture the likely effect size of a new (similar) study based on the included studies. In comparison, confidence intervals reflect the uncertainty around the point estimate but provide an incomplete summary of the underlying heterogeneity in the meta-analysis. This study aimed to estimate (i) the proportion of meta-analysis studies that report a prediction interval in sports medicine; and (ii) the proportion of studies with a discrepancy between the reported confidence interval and a calculated prediction interval. METHODS: We screened, at random, 1500 meta-analysis studies published between 2012 and 2022 in highly ranked sports medicine and medical journals. Articles that used a random effect meta-analysis model were included in the study. We randomly selected one meta-analysis from each article to extract data from, which included the number of estimates, the pooled effect, and the confidence and prediction interval. RESULTS: Of the 1500 articles screened, 866 (514 from sports medicine) used a random effect model. The probability of a prediction interval being reported in sports medicine was 1.7% (95% CI = 0.9%, 3.3%). In medicine the probability was 3.9% (95% CI = 2.4%, 6.6%). A prediction interval was able to be calculated for 220 sports medicine studies. For 60% of these studies, there was a discrepancy in study findings between the reported confidence interval and the calculated prediction interval. Prediction intervals were 3.4 times wider than confidence intervals. CONCLUSION: Very few meta-analyses report prediction intervals and hence are prone to missing the impact of between-study heterogeneity on the overall conclusions. The widespread misinterpretation of random effect meta-analyses could mean that potentially harmful treatments, or those lacking a sufficient evidence base, are being used in practice. Authors, reviewers, and editors should be aware of the importance of prediction intervals.

Potential role of passively increased muscle temperature on contractile function.

Declines in muscle force, power, and contractile function can be observed in older adults, clinical populations, inactive individuals, and injured athletes. Passive heating exposure (e.g., hot baths, sauna, or heated garments) has been used for health purposes, including skeletal muscle treatment. An acute increase in muscle temperature by passive heating can increase the voluntary rate of force development and electrically evoked contraction properties (i.e., time to peak twitch torque, half-relation time, and electromechanical delay). The improvements in the rate of force development and evoked contraction assessments with increased muscle temperature after passive heating reveal peripheral mechanisms' potential role in enhancing muscle contraction. This review aimed to summarise, discuss, and highlight the potential role of an acute passive heating stimulus on skeletal muscle cells to improve contractile function. These mechanisms include increased calcium kinetics (release/reuptake), calcium sensitivity, and increased intramuscular fluid.

Heat Stress Management in the Military: Wet-Bulb Globe Temperature Offsets for Modern Body Armor Systems.

OBJECTIVE: The aim of this study was to model the effect of body armor coverage on body core temperature elevation and wet-bulb globe temperature (WBGT) offset. BACKGROUND: Heat stress is a critical factor influencing the health and safety of military populations. Work duration limits can be imposed to mitigate the risk of exertional heat illness and are derived based on the environmental conditions (WBGT). Traditionally a 3°C offset to WBGT is recommended when wearing body armor; however, modern body armor systems provide a range of coverage options, which may influence thermal strain imposed on the wearer. METHOD: The biophysical properties of four military clothing ensembles of increasing ballistic protection coverage were measured on a heated sweating manikin in accordance with standard international criteria. Body core temperature elevation during light, moderate, and heavy work was modeled in environmental conditions from 16°C to 34°C WBGT using the heat strain decision aid. RESULTS: Increasing ballistic protection resulted in shorter work durations to reach a critical core temperature limit of 38.5°C. Environmental conditions, armor coverage, and work intensity had a significant influence on WBGT offset. CONCLUSION: Contrary to the traditional recommendation, the required WBGT offset was >3°C in temperate conditions (<27°C WBGT), particularly for moderate and heavy work. In contrast, a lower WBGT offset could be applied during light work and moderate work in low levels of coverage. APPLICATION: Correct WBGT offsets are important for enabling adequate risk management strategies for mitigating risks of exertional heat illness.

Monitoring heat strain: the effect of sensor type and location on single-site and mean skin temperature during work in the heat.

PURPOSE: Elevations in skin temperature and heat strain reduce tolerance to work in the heat. This study assessed agreement between mean (eight sites) and single-site skin temperature, measured by a conductive or infrared sensor, during exercise in the heat. METHODS: Twelve males (age: 24.2 ± 3.7 years; height: 180 ± 6.5 cm; body mass: 82.9 ± 9.5 kg; body fat: 16.0 ± 6.5%) volunteered to participate in two trials. Thirty minutes of seated rest was followed by 60 min of treadmill walking (4.5 km·h-1, 1%) inside an environmental chamber (35.5 ± 0.2 °C dry bulb, 50.7 ± 2.5% relative humidity) wearing either an athletic (ATH: t-shirt, shorts, shoes) or a chemical protective ensemble (CPE: ATH plus coverall and respirator). Skin temperature was measured on the axilla with a conductive sensor (Tsk-C) and an infrared sensor (Tsk-I) and compared to mean skin temperature ([Formula: see text] 8-site conductive sensors). Rectal temperature and heart rate were measured and used to calculate the adaptive physiological strain index (aPSI). RESULTS: Skin temperature on the chest, scapula, and thigh showed acceptable agreement with [Formula: see text] (mean difference < 0.5 °C and limits of agreement ± 1.0 °C) in both ATH and CPE. Skin temperature on the axilla overestimated [Formula: see text] in ATH (Tsk-C: 1.5 ± 0.8 °C; Tsk-I: 2.2 ± 1.2 °C) and CPE (Tsk-C: 1.1 ± 0.9 °C; Tsk-I: 1.8 ± 1.1 °C). Significant differences (p < 0.001) were observed in aPSI using Tsk-I (ATH: 5.7 ± 1.0, CPE: 8.3 ± 1.1) and Tsk-C (ATH: 5.4 ± 1.0, CPE 7.8 ± 1.0) compared to [Formula: see text] (ATH: 5.2 ± 1.0, CPE: 7.4 ± 1.0). CONCLUSION: The overestimate of mean skin temperature had a significant influence on the aPSI, which has important implications for real-time monitoring and risk management of personnel working in hot environments.

Short-term heat acclimation preserves knee extensor torque but does not improve 20 km self-paced cycling performance in the heat.

PURPOSE: This study investigated the effect of 5 days of heat acclimation training on neuromuscular function, intestinal damage, and 20 km cycling (20TT) performance in the heat. METHODS: Eight recreationally trained males completed two 5-day training blocks (cycling 60 min day-1 at 50% peak power output) in a counter-balanced, cross-over design, with a 20TT completed before and after each block. Training was conducted in hot (HA: 34.9 ± 0.7 °C, 53 ± 4% relative humidity) or temperate (CON: 22.2 ± 2.6 °C, 65 ± 8% relative humidity) environment. All 20TTs were completed in the heat (35.1 ± 0.5 °C, 51 ± 4% relative humidity). Neuromuscular assessment of knee extensors (5 × 5 s maximum voluntary contraction; MVC) was completed before and after each 20TT and on the first and last days of each training block. RESULTS: MVC torque was statistically higher after 5 days of HA training compared to CON (mean difference = 14 N m [95% confidence interval; 6, 23]; p < 0.001; d = 0.77). However, 20TT performance after 5 days of HA training was not statistically different to CON, with a between-conditions mean difference in the completion time of 68 s [95% confidence interval; - 9, 145] (p = 0.076; d = 0.35). CONCLUSION: Short-term heat acclimation training may increase knee extensor strength without changes in central fatigue or intestinal damage. Nevertheless, it is insufficient to improve 20 km self-paced cycling performance in the heat compared to workload-matched training in a temperate environment. These data suggest that recreationally trained athletes gain no worthwhile performance advantage from short-term heat-training before competing in the heat.

Analysing the predictive capacity and dose-response of wellness in load monitoring.

This study aimed to identify the predictive capacity of wellness questionnaires on measures of training load using machine learning methods. The distributions of, and dose-response between, wellness and other load measures were also examined, offering insights into response patterns. Data (n= 14,109) were collated from an athlete management systems platform (Catapult Sports, Melbourne, Australia) and were split across three sports (cricket, rugby league and football) with data analysis conducted in R (Version 3.4.3). Wellness (sleep quality, readiness to train, general muscular soreness, fatigue, stress, mood, recovery rating and motivation) as the dependent variable, and sRPE, sRPE-TL and markers of external load (total distance and m.min-1) as independent variables were included for analysis. Classification and regression tree models showed high cross-validated error rates across all sports (i.e., > 0.89) and low model accuracy (i.e., < 5% of variance explained by each model) with similar results demonstrated using random forest models. These results suggest wellness items have limited predictive capacity in relation to internal and external load measures. This result was consistent despite varying statistical approaches (regression, classification and random forest models) and transformation of wellness scores. These findings indicate practitioners should exercise caution when interpreting and applying wellness responses.

The Effect of Overreaching on Neuromuscular Performance and Wellness Responses in Australian Rules Football Athletes.

Campbell, PG, Stewart, IB, Sirotic, AC, and Minett, GM. Title: The effect of overreaching on neuromuscular performance and wellness responses in Australian rules football athletes. J Strength Cond Res 34(6): 1530-1538, 2020-This study seeks to evaluate the effect of periodized fluctuations in training load on wellness and psychological questionnaires, perceived exertion, performance, and neuromuscular measures in team-sport athletes. Thirteen amateur Australian rules football athletes completed 6 weeks of periodized training, consisting of 2-week normal training (NT), intensified training (IT), and taper training (TT). Training sessions were quantified using global positioning system devices, heart-rate, and session rating of perceived exertion (sRPE), with wellness (general soreness, sleep quality/quantity, readiness to train, fatigue, stress, mood, and motivation) questionnaires collected daily. Psychological (Recovery-Stress Questionnaire for Athletes) and physical performance (countermovement jump, cycle ergometer peak power, 30-m sprint, and 2-km time trial) markers were measured after each training period. Perceived (sRPE) and mechanical loading were higher for IT than NT, and IT than TT (p < 0.03; d = 0.65-25.34). Cycle ergometer peak power, 30-m sprint, 2-km time trial, and countermovement jump height showed reductions in performance after IT compared to initial testing (p < 0.02; d = 0.51-1.46), with subsequent increases in performance after TT (p < 0.04; d = 0.66-2.27). Average wellness was higher during NT compared to IT (p = 0.005; d = 1.11). Readiness to train did not significantly differ from NT to IT or TT (p < 0.55; d = <0.59); however, readiness to train did improve during TT after the IT (p = 0.01; d = 1.05). The disturbances in performance, perceptual, and mood states may indicate a state of functional overreaching. The findings suggest that an averaged wellness score may be useful in potentially identifying overreaching. However, despite the popularity of wellness in monitoring systems, these measures overall demonstrated a limited capacity to differentiate between periodized fluctuations in load.

Thermal Infrared Imaging Can Differentiate Skin Temperature Changes Associated With Intense Single Leg Exercise, But Not With Delayed Onset of Muscle Soreness.

Muscle damage and soreness associated with increased exercise training loads or unaccustomed activity can be debilitating and impact the quality of subsequent activity/performance. Current techniques to assess muscle soreness are either time consuming, invasive or subjective. Infrared thermography has been identified as a quick, non-invasive, portable and athlete friendly method of assessing skin temperature. This study assessed the capability of thermal infrared imaging to detect skin temperature changes that may accompany the inflammatory response associated with delayed onset muscular soreness (DOMS). Eight recreationally trained participants (age 25 ± 3 years, mass 74.9 ± 13.6 kg, training minutes 296 ± 175 min·wk-1) completed 6 sets of 25 maximal concentric/eccentric contractions of the right knee flexors/extensors on a dynamometer to induce muscle damage and DOMS. The left knee extensors acted as a non-exercise control. Neuromuscular performance, subjective pain assessment and infrared thermography were undertaken at baseline, 24 and 48 hr post the DOMS-inducing exercise protocol. Data were analysed using Bayesian hierarchical regression and Cohen's d was also calculated. Maximal voluntary contraction torque was statistically lower at 24 hr (d = -0.70) and 48 hr (d = -0.52) compared to baseline, after the DOMS-inducing exercise protocol. These neuromuscular impairments coincided with statistically higher ratings of muscle soreness at 24 hr (d = 0.96) and 48 hr (d = 0.48). After adjusting for ambient temperature, anterior thigh skin temperature was statistically elevated at 24 hr, but not 48 hr, compared with baseline, in both the exercised and non-exercised leg. Thigh temperature was not different statistically between legs at these time points. Infrared imaging was able to detect elevations in skin temperature, at 24 hrs after the DOMS inducing exercise protocol, in both the exercised and non-exercised thigh. Elevations in the skin temperature of both thighs, potentially identifies a systemic inflammatory response occurring at 24 hr after the DOMS-inducing exercise protocol.

Acute glutamine supplementation does not improve 20-km self-paced cycling performance in the heat.

INTRODUCTION: The premise of this study was to investigate the effect of acute glutamine supplementation on 20 km time trial cycling performance in the heat, neuromuscular function, inflammation and endotoxemia. METHODS: Twelve cyclists completed two, 20-km time trials (20TT) in 35 °C (50% relative humidity). Participants ingested either glutamine (GLUT; 0.9 g kg-1 fat-free mass) or a placebo (CON) 60 min before each 20TT. Physiological and perceptual measures were recorded during each 20TT, and neuromuscular function assessed pre- and post-exercise. Venous blood was analysed for endotoxins, markers of gut damage (inflammatory fatty acid binding protein; I-FABP) and inflammatory cytokines (interleukin-6, IL-6; tumour necrosis factor-alpha, TNF-α). Data were analysed using linear mixed models in a Bayesian framework. RESULTS: 20TT in the heat increased I-FABP and elevated inflammatory cytokines (IL-6 and TNF-α) compared to pre-exercise values but did not result in endotoxemia. Completion time was not statistically different between conditions (mean difference [95% credible interval] = 11 s [- 23, 44]). Relative to CON, GLUT did not alter any physiological or perceptual measures during the 20TT. CONCLUSION: Glutamine supplementation does not improve 20TT performance in the heat or preserve neuromuscular function when compared to a placebo. These findings suggest that glutamine is not an ergogenic aid or prophylactic intervention for heat-induced gut damage during short-duration self-paced exercise in hot environments.

The effect of cycling in the heat on gastrointestinal-induced damage and neuromuscular fatigue.

PURPOSE: This study investigated the effect of exercise in the heat on neuromuscular function, gastrointestinal damage, endotoxemia and inflammatory cytokines. METHODS: Eight male cyclists completed two 60 min cycling trials in both hot (HOT 34.5 ± 0.1 °C and 53 ± 1% relative humidity) and temperate environments (CON 20.2 ± 0.3 °C and 55 ± 3% relative humidity). The cycling task comprised of alternating 3 min intervals at a moderate-vigorous intensity (50% and 70% of maximum power output; Pmax) for 30 min, followed by 30 min at moderate intensity (40-50% Pmax). Neuromuscular function was assessed at pre-, post-exercise and 60 min post-exercise. Circulating levels of endotoxins, inflammatory cytokines and markers of gut permeability and damage were also collected at these time points. Heart rate, core temperature, skin temperature, perceived exertion, thermal sensation and comfort were also measured. RESULTS: Post-exercise voluntary activation of HOT (87.9% [85.2, 90.8]) was statistically lower (mean difference - 2.5% [- 4.5, - 0.5], d = 2.50) than that of CON (90.5% [87.8, 93.2]). The HOT trial resulted in statistically elevated (+ 69%) markers of gastrointestinal damage compared to CON (mean difference 0.424 ng mL-1 [0.163, 0.684, d = - 3.26]), although this was not observed for endotoxin, other inflammatory markers, or gastrointestinal permeability. CONCLUSIONS: This research provides evidence that short-duration cycling in the heat results in sub-optimal neuromuscular activation and increased expression of gastrointestinal damage markers, without a simultaneous elevation in circulating endotoxins or pro-inflammatory cytokines.

Indices of physiological strain for firefighters of the Australian Defence Forces.

High levels of exertion and physiological strain are the leading cause of fireground injuries. The Physiological Strain Index (PSI) provides a rating of strain based on body core temperature and heart rate; however, it may underestimate the strain of workers in protective clothing as skin temperature may be elevated. This study aimed to examine the relationship between the PSI and an Adaptive Physiological Strain Index (aPSI) that incorporates skin temperature, among firefighters wearing protective clothing. Nine male firefighters of the Australian Defence Force volunteered to participate. Participants conducted scenario-based activities while wearing turnout gear and breathing apparatus. Working in teams of four, participants would respond to a situation around and within a small building with several rooms that could be filled with smoke, however, no live fire was present. Heart rate, gastrointestinal temperature, and skin temperature were monitored throughout work and rehabilitation. Physiological strain was estimated via the PSI and aPSI. Absolute peak PSI and aPSI ratings were significantly different during work (PSI: 7.3 ± 1.6; aPSI 8.2 ± 2.0; p < 0.001). The aPSI produced higher ratings of physiological strain, >0.5 above PSI, progressively from a moderate level of strain (>6). The aPSI may provide a more accurate indication of a level of "maximal strain" for encapsulated workers than the original PSI, coincident with the occupational limits for body core temperature of 38.0 °C for general occupational groups, or 38.5 °C for selected and acclimatised personnel.

Human runners exhibit a least variable gait speed.

This study characterises the relationship between gait variability and speed in runners using data from trunk accelerations in each axis. Twelve participants of varying fitness ran on the treadmill with three sessions of six randomly ordered self-selected speeds. A VO2max test was conducted on the fourth session. Running gait was tracked with inertial sensors. The occurrence of a mid-range speed was analysed for the anterior-posterior, vertical and lateral directional coefficient of variation (CV) of root mean square (RMS) acceleration data. One participant with noisy gait signals was omitted. The results show all remaining participants consistently showed significant quadratic U-shaped relationships between vertical RMS CV acceleration and speed. Neither anterior-posterior nor lateral RMS CV acceleration were clearly related to speed. These least variable gait speeds were similar to estimates of optimal speed derived from minimum cost of transport with speed. In conclusion, there exists a mid-range speed for each runner with the least variable gait in the vertical direction, and this occurred significantly more often than would be expected by chance (P < 0.05). However, there are no prominent patterns for the anterior-posterior and lateral directions. This finding supports anecdotal evidence from runners and coaches concerning gait consistency.

The Pandolf load carriage equation is a poor predictor of metabolic rate while wearing explosive ordnance disposal protective clothing.

This investigation aimed to quantify metabolic rate when wearing an explosive ordnance disposal (EOD) ensemble (~33kg) during standing and locomotion; and determine whether the Pandolf load carriage equation accurately predicts metabolic rate when wearing an EOD ensemble during standing and locomotion. Ten males completed 8 trials with metabolic rate measured through indirect calorimetry. Walking in EOD at 2.5, 4.0 and 5.5km·h-1 was significantly (p < 0.05) greater than matched trials without the EOD ensemble by 49% (127W), 65% (213W) and 78% (345W), respectively. Mean bias (95% limits of agreement) between predicted and measured metabolism during standing, 2.5, 4 and 5.5km·h-1 were 47W (19 to 75W); -111W (-172 to -49W); -122W (-189 to -54W) and -158W (-245 to -72W), respectively. The Pandolf equation significantly underestimated measured metabolic rate during locomotion. These findings have practical implications for EOD technicians during training and operation and should be considered when developing maximum workload duration models and work-rest schedules. Practitioner Summary: Using a rigorous methodological design we quantified metabolic rate of wearing EOD clothing during locomotion. For the first time we demonstrated that metabolic rate when wearing this ensemble is greater than that predicted by the Pandolf equation. These original findings have significant implications for EOD training and operation.

Whole-body cryotherapy (extreme cold air exposure) for preventing and treating muscle soreness after exercise in adults.

BACKGROUND: Recovery strategies are often used with the intention of preventing or minimising muscle soreness after exercise. Whole-body cryotherapy, which involves a single or repeated exposure(s) to extremely cold dry air (below -100 °C) in a specialised chamber or cabin for two to four minutes per exposure, is currently being advocated as an effective intervention to reduce muscle soreness after exercise. OBJECTIVES: To assess the effects (benefits and harms) of whole-body cryotherapy (extreme cold air exposure) for preventing and treating muscle soreness after exercise in adults. SEARCH METHODS: We searched the Cochrane Bone, Joint and Muscle Trauma Group Specialised Register, the Cochrane Central Register of Controlled Trials, MEDLINE, EMBASE, CINAHL, the British Nursing Index and the Physiotherapy Evidence Database. We also searched the reference lists of articles, trial registers and conference proceedings, handsearched journals and contacted experts.The searches were run in August 2015. SELECTION CRITERIA: We aimed to include randomised and quasi-randomised trials that compared the use of whole-body cryotherapy (WBC) versus a passive or control intervention (rest, no treatment or placebo treatment) or active interventions including cold or contrast water immersion, active recovery and infrared therapy for preventing or treating muscle soreness after exercise in adults. We also aimed to include randomised trials that compared different durations or dosages of WBC. Our prespecified primary outcomes were muscle soreness, subjective recovery (e.g. tiredness, well-being) and adverse effects. DATA COLLECTION AND ANALYSIS: Two review authors independently screened search results, selected studies, assessed risk of bias and extracted and cross-checked data. Where appropriate, we pooled results of comparable trials. The random-effects model was used for pooling where there was substantial heterogeneity. We assessed the quality of the evidence using GRADE. MAIN RESULTS: Four laboratory-based randomised controlled trials were included. These reported results for 64 physically active predominantly young adults (mean age 23 years). All but four participants were male. Two trials were parallel group trials (44 participants) and two were cross-over trials (20 participants). The trials were heterogeneous, including the type, temperature, duration and frequency of WBC, and the type of preceding exercise. None of the trials reported active surveillance of predefined adverse events. All four trials had design features that carried a high risk of bias, potentially limiting the reliability of their findings. The evidence for all outcomes was classified as 'very low' quality based on the GRADE criteria.Two comparisons were tested: WBC versus control (rest or no WBC), tested in four studies; and WBC versus far-infrared therapy, also tested in one study. No studies compared WBC with other active interventions, such as cold water immersion, or different types and applications of WBC.All four trials compared WBC with rest or no WBC. There was very low quality evidence for lower self-reported muscle soreness (pain at rest) scores after WBC at 1 hour (standardised mean difference (SMD) -0.77, 95% confidence interval (CI) -1.42 to -0.12; 20 participants, 2 cross-over trials); 24 hours (SMD -0.57, 95% CI -1.48 to 0.33) and 48 hours (SMD -0.58, 95% CI -1.37 to 0.21), both with 38 participants, 2 cross-over studies, 1 parallel group study; and 72 hours (SMD -0.65, 95% CI -2.54 to 1.24; 29 participants, 1 cross-over study, 1 parallel group study). Of note is that the 95% CIs also included either no between-group differences or a benefit in favour of the control group. One small cross-over trial (9 participants) found no difference in tiredness but better well-being after WBC at 24 hours post exercise. There was no report of adverse events.One small cross-over trial involving nine well-trained runners provided very low quality evidence of lower levels of muscle soreness after WBC, when compared with infrared therapy, at 1 hour follow-up, but not at 24 or 48 hours. The same trial found no difference in well-being but less tiredness after WBC at 24 hours post exercise. There was no report of adverse events. AUTHORS' CONCLUSIONS: There is insufficient evidence to determine whether whole-body cryotherapy (WBC) reduces self-reported muscle soreness, or improves subjective recovery, after exercise compared with passive rest or no WBC in physically active young adult males. There is no evidence on the use of this intervention in females or elite athletes. The lack of evidence on adverse events is important given that the exposure to extreme temperature presents a potential hazard. Further high-quality, well-reported research in this area is required and must provide detailed reporting of adverse events.

Inside the 'Hurt Locker': The Combined Effects of Explosive Ordnance Disposal and Chemical Protective Clothing on Physiological Tolerance Time in Extreme Environments.

BACKGROUND: Explosive ordnance disposal (EOD) technicians are often required to wear specialized clothing combinations that not only protect against the risk of explosion but also potential chemical contamination. This heavy (>35kg) and encapsulating ensemble is likely to increase physiological strain by increasing metabolic heat production and impairing heat dissipation. This study investigated the physiological tolerance times of two different chemical protective undergarments, commonly worn with EOD personal protective clothing, in a range of simulated environmental extremes and work intensities METHODS: Seven males performed 18 trials wearing 2 ensembles. The trials involved walking on a treadmill at 2.5, 4, and 5.5 km h(-1) at each of the following environmental conditions, 21, 30, and 37°C wet bulb globe temperature. The trials were ceased if the participants' core temperature reached 39°C, if heart rate exceeded 90% of maximum, if walking time reached 60min or due to volitional fatigue. RESULTS: Physiological tolerance times ranged from 8 to 60min and the duration (mean difference: 2.78min, P > 0.05) were similar in both ensembles. A significant effect for environment (21 > 30 > 37°C wet bulb globe temperature, P < 0.05) and work intensity (2.5 > 4 > 5.5 km h(-1), P < 0.05) was observed in tolerance time. The majority of trials across both ensembles (101/126; 80.1%) were terminated due to participants achieving a heart rate equivalent to greater than 90% of their maximum. CONCLUSIONS: Physiological tolerance times wearing these two chemical protective undergarments, worn underneath EOD personal protective clothing, were similar and predominantly limited by cardiovascular strain.

The effect of using different regions of interest on local and mean skin temperature.

The dynamic nature of tissue temperature and the subcutaneous properties, such as blood flow, fatness, and metabolic rate, leads to variation in local skin temperature. Therefore, we investigated the effects of using multiple regions of interest when calculating weighted mean skin temperature from four local sites. Twenty-six healthy males completed a single trial in a thermonetural laboratory (mean ± SD): 24.0 (1.2)°C; 56 (8%) relative humidity; <0.1 m/s air speed). Mean skin temperature was calculated from four local sites (neck, scapula, hand and shin) in accordance with International Standards using digital infrared thermography. A 50 mm × 50 mm, defined by strips of aluminium tape, created six unique regions of interest, top left quadrant, top right quadrant, bottom left quadrant, bottom right quadrant, centre quadrant and the entire region of interest, at each of the local sites. The largest potential error in weighted mean skin temperature was calculated using a combination of a) the coolest and b) the warmest regions of interest at each of the local sites. Significant differences between the six regions interest were observed at the neck (P<0.01), scapula (P<0.001) and shin (P<0.05); but not at the hand (P = 0.482). The largest difference (± SEM) at each site was as follows: neck 0.2 (0.1)°C; scapula 0.2 (0.0)°C; shin 0.1 (0.0)°C and hand 0.1 (0.1)°C. The largest potential error (mean ± SD) in weighted mean skin temperature was 0.4 (0.1)°C (P<0.001) and the associated 95% limits of agreement for these differences was 0.2-0.5 °C. Although we observed differences in local and mean skin temperature based on the region of interest employed, these differences were minimal and are not considered physiologically meaningful.

Passive heat therapy: a promising preventive measure for people at risk of adverse health outcomes during heat extremes.

The world is experiencing increased frequency, duration, and severity of life-threatening heat extremes. Most hospitalizations and excess deaths during extreme heat events are associated with preexisting diseases in older adults. As climate change persists, the global population ages and the number of individuals with chronic diseases expands, more people are at risk of adverse health outcomes during extreme heat events. Therefore, proactive preventive measures are urgently needed to mitigate heat-related health risks within these populations. In this context, passive heat therapy (e.g., hot baths, saunas, and water-perfused suits) emerges as a promising countermeasure to improve physiological resilience to a warming planet. Passive heating improves cardiovascular function and overall health in older adults and individuals living with chronic diseases, offering the prospect of reducing cardiovascular strain during hotter days. Moreover, some studies suggest that passive heat therapy can be an effective strategy for heat acclimation (i.e., improved thermoregulation). This review describes the existing literature on the effects of passive heat therapy on cardiovascular and thermoregulatory responses in individuals with higher heat-related health risks and explores the use of passive heating as a strategy for heat acclimation to mitigate health risks during extreme heat events.NEW & NOTEWORTHY Passive heat therapy improves cardiovascular function and health in middle-aged and older adults living with or without chronic diseases. In addition, preliminary studies indicate that passive heat interventions can induce heat acclimation, improving thermoregulatory responses. Thus, passive heat therapy could serve as a preventive measure for people at risk of adverse health outcomes during extreme heat events, improving resilience to ongoing climate change.

Trends in menstrual cycle symptoms, physical activity avoidance, and hormonal contraceptive use in a general population of adult women.

INTRODUCTION: Research examining symptoms and side effects of the menstrual cycle on physical activity performance and participation has almost exclusively focussed on elite and athletic populations. The current study aimed to i) identify any differences in symptomatic experiences of the menstrual cycle between hormonal contraceptive users and non-users, ii) gain insight into hormonal contraceptive use, iii) describe perceived symptomatic influences on physical activity engagement, and iv) identify perceived levels of knowledge and understanding around the menstrual cycle. METHODS: An online questionnaire was completed by 881 adult females aged between 18 and 55 years. Questionnaire items related to hormonal contraceptive use, habitual physical activity levels, experiences and symptoms of the menstrual cycle, and sources of information resulting in knowledge and understanding of the menstrual cycle. RESULTS: More than half of all participants (52%) identified themselves as being recreationally active, and the most commonly reported menstrual symptoms were abdominal cramps, lethargy, abdominal bloating, lower back pain, and heavy bleeding. Of all respondents, 48.1% were using some form of hormonal contraception, 66% of which were using a version of a combined oral contraceptive pill. DISCUSSION: Consistent with previous studies, 90% of respondents regularly experienced adverse menstrual symptoms, including abdominal cramps, lethargy, abdominal bloating, lower back pain, and heavy bleeding. Menstrual symptoms were frequently identified as influential factors in the avoidance of, and reduced performance in, physical activity. Almost half of all participants were using some form of hormonal contraception, a noticeably larger proportion than has been previously documented in studies examining non-athletic populations.

The bias for statistical significance in sport and exercise medicine.

OBJECTIVES: We aimed to examine the bias for statistical significance using published confidence intervals in sport and exercise medicine research. DESIGN: Observational study. METHODS: The abstracts of 48,390 articles, published in 18 sports and exercise medicine journals between 2002 and 2022, were searched using a validated text-mining algorithm that identified and extracted ratio confidence intervals (odds, hazard, and risk ratios). The algorithm identified 1744 abstracts that included ratio confidence intervals, from which 4484 intervals were extracted. After excluding ineligible intervals, the analysis used 3819 intervals, reported as 95 % confidence intervals, from 1599 articles. The cumulative distributions of lower and upper confidence limits were plotted to identify any abnormal patterns, particularly around a ratio of 1 (the null hypothesis). The distributions were compared to those from unbiased reference data, which was not subjected to p-hacking or publication bias. A bias for statistical significance was further investigated using a histogram plot of z-values calculated from the extracted 95 % confidence intervals. RESULTS: There was a marked change in the cumulative distribution of lower and upper bound intervals just over and just under a ratio of 1. The bias for statistical significance was also clear in a stark under-representation of z-values between -1.96 and +1.96, corresponding to p-values above 0.05. CONCLUSIONS: There was an excess of published research with statistically significant results just below the standard significance threshold of 0.05, which is indicative of publication bias. Transparent research practices, including the use of registered reports, are needed to reduce the bias in published research.