ECSS Paris 2023: OP-PN22
INTRODUCTION: Heat training (HT; acclimation and acclimatisation) is considered essential for preparing athletes for competition in hot environments. Although laboratory research has informed evidence-based HT guidelines, little is known about how these guidelines are applied in high‑performance settings. This study described current perceptions, considerations, and prescription approaches of practitioners in high‑performance sport. METHODS: Practitioners supporting national- to world-class athletes preparing for competition in hot environments completed an online questionnaire assessing demographics, perceptions, planning considerations, barriers, and HT protocol characteristics. Data is presented as percentages or median (interquartile range [IQR]). RESULTS: Fifty-one practitioners responded, primarily sports scientists/physiologists (72%), based in Europe (45%) and Oceania (23%). Most (73%) had ≥5 years’ experience prescribing HT, 69% had experience with both heat acclimation and acclimatisation, and 73% primarily supported endurance‑based athletes in preparation for competition in hot environments (e.g. Triathlon: 29% and Cycling: 24%). Practitioners reported prescribing HT mainly to induce adaptations (31%) and to familiarise athletes with the expected environmental demands (26%). Nearly all practitioners (96%) considered HT of high importance for competition in hot conditions, whereas only 14% considered HT of high importance for cool conditions. The athlete‑ and competition‑based considerations of high importance for HT were training‑cycle phase/load (73%) and expected competition conditions (94%), respectively. The most common barriers were interference with training (27%) and limited athlete/coach buy‑in (18%). Heat acclimation and acclimatisation interventions typically began 3–5 weeks before competition in hot environments (45% and 44% respectively) and lasted 2–4 weeks (60% and 54% respectively). Active heat acclimation was typically prescribed for a minimum of 2 (2–3) weekly exposures to a maximum of 5 (4–6), with sessions lasting from 45 (30–60) to 90 (75–120) min. Active heat acclimatisation sessions were longer, at 60 (40–60) to 120 (90–180) min. For acclimation and acclimatisation, most practitioners reported that weekly training intensity (46% and 49%) and session frequency (70% and 76%) were consistent with normal training, while weekly volume was either maintained (42% and 50%) or decreased slightly (42% and 38%). CONCLUSION: Around half of practitioners implemented HT within one month of competition and for ≥2 weeks, consistent with current evidence-based guidelines. Active acclimatisation sessions were typically longer than active acclimation sessions. Further insight is needed from practitioners working with non-endurance athletes due to low representation (27%). HT guidelines for high-performance environments should also consider rigid training structures and athlete/coach engagement, given their influence on implementation.
Read CV Josh ElliottECSS Paris 2023: OP-PN22
INTRODUCTION: Although heat-related strain during intermittent exercise is well documented, direct comparisons between contrasting environments (i.e., hot-dry (HD) and warm-humid (WH) environments), especially between sexes, remain limited. This study compared thermal, cardiovascular, and perceptual responses of male and female athletes during intermittent running under temperate (TEM), HD, and WH conditions. METHODS: Twenty-six intermittent-sport athletes (13 males, 13 females) completed three trials, each comprising two 30-min halves (first (H1) and second (H2) half) of high-intensity intermittent treadmill running in TEM (19.9 ± 0.4°C, 55.6 ± 1.5% RH, WBGT: 16.0 ± 0.5°C), HD (40.1 ± 0.4°C, 24.4 ± 1.5% RH, WBGT: 29.0 ± 0.5°C), and WH (31.3 ± 0.4°C, 80.3 ± 1.5% RH, WBGT: 29.3 ± 0.5°C). Exercise intensity was matched between sexes by prescribing running velocities across six zones as a percentage of individual peak sprint velocity. Gastrointestinal temperature (Tgi), skin temperature (Tsk), heart rate (HR), rating of perceived exertion (RPE), whole-body sweat rate (WBSR), and total distance were measured. Water was provided ad libitum, and participants rested in the laboratory before H2. RESULTS: Mean HR, WBSR, RPE, Tsk, and Tgi in H2 were higher in HD and WH compared with TEM (P≤0.004). Physiological and perceptual responses were largely similar between HD and WH (P≥0.280); however, HD elicited higher Tsk (P<0.001) and WBSR (P≤0.004), with an increase in mean HR from H1 to H2 (P=0.048). Although males covered a greater total distance than females (1775 m [1282, 2269]; P<0.001), physiological and perceptual responses did not differ by sex (P≥0.541). A sex × condition interaction was observed for WBSR (P=0.001), with greater values in males than females under HD and WH conditions (P<0.001). A sex × time interaction was observed for mean Tgi (P = 0.048), indicating a differential temporal response between sexes; however, no significant effects were detected at individual time points (P≥0.974). Increases in sweat rate (P<0.001) and HR (P≤0.009) were observed in H2 (compared to H1) for both HD and WH. Despite significant interaction for Tgi (P≤0.048) and RPE (P<0.001), no differences between halves were detected within conditions or sexes (P≥0.078). Similarly, females displayed similar mean Tsk across halves in all conditions (P≥0.835). In contrast, mean Tsk for males did not differ between halves in TEM (P=0.995) but was lower in H2 than H1 in both HD and WH (P≤0.009). CONCLUSION: When matched for WBGT, high-intensity intermittent treadmill running elicited comparable thermal, cardiovascular and perceptual strain across HD and WH in both sexes. However, HD still imposed greater thermal and cardiovascular strain than WH, as reflected by the higher Tsk, HR, and WBSR, despite comparable Tgi responses. The absence of cumulative heat strain across halves was likely attributable to heat dissipation during recovery in the cooler laboratory environment between the halves.
Read CV Joel PangECSS Paris 2023: OP-PN22
INTRODUCTION: Heat acclimation sessions are increasingly integrated into training to improve heat tolerance or enhance oxygen delivery through increased total hemoglobin mass. Physiological responses to heat training are well-documented, while some evidence points towards concomitant anabolic and endocrine adaptations despite scarce data for underpinning mechanisms. This study therefore investigated steroidal and endocrine responses to heat acclimation with two randomized cross-over training interventions. METHODS: Twenty well-trained cyclists and triathletes (11 men and 9 women) were monitored for 9 weeks including two blocks of 10 days of indoor training in temperate (TEMP, 21°, 40% humidity) or hot (HOT, 35°, 60% humidity) conditions in a climatic chamber, separated by 3 weeks wash-out. Along with and sweat rate response, twelve blood samples were collected in total, before, during, and after each training block to monitor variations in serum steroidal (testosterone (T)) and endocrine (Insuline-Like Growth Factor I (IGF-1) and Procollagen type III N-terminal propeptide (P-III-NP)) markers. T, and IGF-1 were measured by liquid-chromatography tandem mass spectrometry (LC-MS/MS), whereas an immunoassay (ADVIA Centaur XP) allowed the analysis of P-III-NP. A repeated measures mixed-effects model with Tukey’s multiple comparisons was used for the analyses. Data are presented as means and standard deviations (±SD) with 95% confidence intervals (CI). HOT led to increases in sweat production (p<0.05) and lower sweat sodium concentrations (p<0.05) at 10 days, suggesting heat acclimation after HOT. Water balance and sweat sodium concentrations were unchanged after TEMP. RESULTS: In female participants, testosterone was stable both in TEMP (0.33 ± 0.03 ng/mL, CI 0.21 to 0.42) and HOT (0.31 ± 0.02 ng/mL, CI 0.22 to 0.40), with no difference between successive time points or condition. In male participants as well, T did not vary with training in TEMP (6.21 ± 0.45 ng/mL, CI 4.87 to 7.55) or HOT (6.15 ± 0.50 ng/mL, CI 4.83 to 7.56), with no difference between successive time points or groups. For endocrine markers, IGF-1 was comparable and stable in TEMP (162.3 ± 4.8 µg/L, CI 140.7 to 183.9) and HOT (168.3 ± 8.2 µg/L, CI 145.1 to 191.6) in all participants. Concentrations for P-III-NP were different at baseline (p<0.01) but did not differ with the training intervention both in TEMP (7.3 ± 0.5 µg/L, CI 6.4 to 8.2) and HOT (5.7 ± 0.6 µg/L, CI 4.9 to 6.6). CONCLUSION: Overall, neither heat nor temperate training altered circulating steroid hormones, as T and A4 remained stable across time and conditions in both female and male participants. Similarly, key endocrine markers related to anabolic and connective tissue processes, including IGF-1, were unaffected by training environment, showing comparable and stable concentrations in HOT and TEMP. In conclusion, 10 days of heat acclimation training did not confer additional steroidal or endocrine adaptations compared with training in temperate conditions.
Read CV Raphael FaissECSS Paris 2023: OP-PN22