ECSS Paris 2023: OP-PN13
INTRODUCTION: This study aimed to investigate the effects of repeated-sprint training performed under different environmental stressors on oxidative stress, inflammatory responses, and muscle damage in elite athletes. METHODS: 22 elite athletes from the French national rugby sevens and cycling teams were randomly assigned to a repeated-sprint training program (3x 5, 7-10s sprints with 20-23s passive rest) conducted either in normobaric hypoxia (FiO₂ 14.5%, 20-22°C; RSHyp) or in hot conditions (FiO₂ 20.9%, 36°C; RSHot). The intervention consisted of three RSHyp/RSHot sessions per week over a 2-week intervention period. Blood samples were collected after 15 min of supine rest at rest before (Pre) and after (Post) the intervention. Biomarkers related to redox balance (antioxidant, pro-oxidant enzymes, oxidative damage markers), inflammation (TNF-α, IL-1β, IL-6, CRP), muscle damage (CK, Mb), hypoxic signaling (HIF-1α), cellular stress (HSP70, HSP90), nitrosative stress (nitrotyrosine) were analyzed. RESULTS: Following the intervention, HIF-1α and HSP70 concentrations increased in both groups, indicating activation of hypoxic and cellular stress pathways. In RSHyp , post-intervention increases were observed in catalase, XO, MPO, CK, TNF-α, and IL-6 (all p<0.05), reflecting enhanced oxidative and inflammatory responses. In contrast, RSHot showed a significant decrease in SOD and an increase in Mb levels (p<0.05), suggesting greater muscle membrane stress and lipid peroxidation. CONCLUSION: These findings support the existence of biological crosstalk between hypoxia and heat stress when combined with repeated-sprint training, particularly through HIF-1α and HSP signaling. However, in this special training modality, hypoxia preferentially amplified pro-oxidant and pro-inflammatory responses, whereas heat exposure predominantly increased lipid peroxidation. This highlights the stressor-specific nature of molecular adaptations to environmental training conditions.
Read CV Marie Chambion-DiazECSS Paris 2023: OP-PN13
INTRODUCTION: This study examined whether heat acclimation (HA), and HA with blood flow restriction (BFR) could attenuate cognition and neuromuscular function impairments in cognitive-motor dual-task (CMDT) during exercise-heat stress. METHODS: Twenty trained adults were randomly assigned to one of two HA protocols over six sessions (~8 days). Each session consisted of 4×8-min self-regulated cycling intervals (5-min “strong effort”, 3-min “moderate effort”) in temperate conditions (20°C), immediately followed by 40-min hot water immersion (40°C). One group exercised with BFR applied during the “strong” bouts (50% arterial occlusion pressure; BFRHA), whereas the control group completed without occlusion (CTRLHA). Before and after HA protocols, participants completed an exercise-heat stress test with CMDT (pre- post-HA; 40°C, 40% RH): 1×7-min self-regulated cycling (“strong effort”) followed by 2×7-min fixed-power blocks with a sustained attention task (SART). Heart rate (HR), rectal temperature (Trec), and perceived mental effort were recorded, while neuromuscular function (voluntary activation, peripheral responses) was assessed post-CMDT during a 1-min sustained maximal voluntary contraction. RESULTS: During HA sessions, HR and Trec where comparable between groups (P≥0.19), despite a reduced power during BFRHA (-22±6%; P<0.001). Post-HA, both groups reduced peak HR (-6±6 bpm) and Trec (-0.2±0.2°C; P≤0.003). Both improved SART performance (+10±4%, P<0.001) with lower mental effort, while reduced force loss was evident only in BFRHA post-HA (+18±12%, P=0.001), consistent with lower central fatigue (P=0.028) versus pre-HA. CONCLUSION: Effective heat adaptations were induced by both HA protocols, despite the lower workload with BFR. Both approaches enhanced sustained attention during an exercise-heat stress with CMDT, while BFR additionally mitigated central fatigue.
Read CV Thomas GoeppECSS Paris 2023: OP-PN13
INTRODUCTION: The exercise employed within a heat acclimation (HA) protocol is recommended to be similar to the sporting demands of the competition in the heat [1,2]. It remains unclear however, if the magnitude of adaptations transfers to different patterns of exercise after high intensity intermittent heat acclimation. The aim of this study was to determine whether thermophysiological and perceptual adaptations from high intensity intermittent heat acclimation transfer differently when females perform continuous versus intermittent heat response tests. METHODS: Eleven non-heat acclimatised females (mean ± SEM: age 27±2 y; body mass 69.63±2.64 kg; V̇O2peak 39.70±1.05 mL.kg-1.min-1; body surface area 1.78±0.04 m2) of recreationally active to highly trained status [3], completed six, 60-min sessions of intermittent (Int) cycling (repeated 30 s intervals) in the heat (~ 40°C, ~ 40% relative humidity) over seven days in the follicular phase of the menstrual cycle. In a randomised and balanced design, participants completed a 60 min Continuous (Con) and Int heat stress test (HST) both before HA (~ 33-34 ± 7 days) and after HA (2- and 4-days). All exercise sessions (HA and HST) were matched for mean external work-rate and designed to elicit ~ 60% V̇O2peak. Key outcome measures included delta change in rectal temperature (ΔTre), skin temperature (ΔTsk), heart rate (ΔHR), as well as rating of perceived exertion (ΔRPE), and thermal discomfort (ΔTD) for pre- and post- Int and Con HST only. Linear mixed models with Bonferroni post-hoc procedures were used to identify differences, with results considered statistically significant when p<0.05, and presented as mean ± 95% confidence intervals (CI). RESULTS: Following Int HA, ΔHR was 12 beats.min-1 [95%CI: 2, 21; p=0.015) lower during Int HST (pre-post: -15 beats.min-1) compared to Con HST (pre-post; -3 beats.min-1). A HA main effect for a reduction in ΔTre (-0.2°C [95%CI: -0.3, 0.0]; p=0.010), ΔTsk (-1.0°C [95%CI: -1.4, -0.6]; p<0.001), ΔRPE (-1.8 AU [95%CI: -2, -1]; p<0.001) and ΔTD (-163 mm [95%CI: -252, -76]; p<0.001) was identified and irrespective of HST. CONCLUSION: Following the Int HA protocol in females, there was a greater extent of transfer for mean HR only during the Int HST. All other thermophysiological and perceptual adaptations induced with Int HA transferred similarly to both Int and Con HST. 1. Racinais et al. (2015) Scan J Med Sci Sport, 2. Casadio et al. (2017) Sports Med., 3 McKay et al. (2022) IJSPP.
Read CV Monica KellyECSS Paris 2023: OP-PN13