ECSS Paris 2023: CP-PN02
INTRODUCTION: Increasing hot weather and global temperatures place athletes and outdoor workers at increasing risk of Exertional Heat Illness (EHI). Heat Tolerance Assessment (HTA) has been used in surrogate for future EHI risk, in order to inform decisions on athletic return-to-play and occupational readiness, with protocols often attempting to dichotomise HTA outcomes as pass/fail. However, no international consensus exists in this area of preventative sports medicine. Furthermore, heat tolerance falls on a spectrum that may vary with individual factors including aerobic fitness and heat adaptation (acclimation or acclimatisation). In our experience, concerns arise for fitter individuals, who may pass HTA conducted at relative exercise intensity, but go on to suffer EHI with subsequent exercise-heat stress (i.e. false negative HTA result). We report data concerning metabolic responses to HTA tailored to individual factors in elite, well-trained and recreationally active athletes, and our progress towards better prognosticating EHI risk in the more highly trained. METHODS: Comprehensive observations of exercising heat tolerance in the elite class of athlete were made before and during a structured laboratory acclimation protocol. Results were used to construct HTA based on the work of Mee et al,(1) with an extension phase of the protocol tailored to lactate thresholds. Two groups of athlete were then recruited from well-trained (WT) and recreationally active (RA) groups. Each participant performed running HTA (30 min at LT1 followed immediately by 30 min at LT2, 1% gradient, 40°C and 40% relative humidity) on two days one week apart (HTA1 and HTA2), without intervening heat adaptation. RESULTS: Development of the HTA in elite running will be presented. As applied to WT and RA groups, HTA1 vs HTA2 showed no significant differences (P<0.05) at end exercise in core temperature (39.20 ± 0.44°C vs HTA2: 39.13 ± 0.46°C), skin temperature (38.83 ± 0.73°C vs. 38.44 ± 0.73°C), heart rate (181.20 ± 10.76 b·min-1 vs 178.00 ± 10.07 b·min-1), sweat rate (1.46 ± 0.48 kg·hour-1 vs1.25 ± 0.49 kg·hour-1), blood lactate (3.21 ± 1.41mmol·L-1 vs. 3.08 ± 1.34 mmol·L-1) or perceptual scores. Robust agreement between HTA1 and HTA2 was reflected in significant correlations and minimal participant variability on repeatability scoring. Nevertheless, the coefficient of variation was consistently lower for the WT group than the RA group, despite WT achieving significantly higher core body temperature than RA (WT: 39.50 ± 0.00, RA: 38.94 ± 0.42). CONCLUSION: Our results imply that the HTA is a reliable indicator of physiological and perceptual strain in hot conditions, with increased reliability in fitter individuals. Further work is required to understand its repeatability with heat acclimation and accuracy in predicting recovery from, and future susceptibility to, EHI. 1. Mee, J. A., Doust, J. and Maxwell, N. S. (2015) Repeatability of a running heat tolerance test. Journal of Thermal Biology, 49, pp. 91-97.
Read CV Thomas PalinECSS Paris 2023: CP-PN02
INTRODUCTION: There is a decrease in daily energy expenditure in women during mid-life regardless of menopause stage, but oestrogen deficiency also leads to reduced resting, sleeping, exercise and total energy expenditure. Identifying the deficit in exercise energy expenditure that can be attributed to menopause will aid the development of specific exercise prescription guidance, which may support healthy ageing in and after menopause. This study aimed to evaluate the impact of perimenopause and postmenopause on exercise energy expenditure and respiratory exchange ratio during exercise to maximal intensity. METHODS: 53 women (PRE: 27 ± 4 yr; PERI: 47 ± 5 yrs; POST: 55 ± 3 yrs; 167.8 ± 5.2 cm, 69.3 ± 9.8 kg), categorised as premenopausal (PRE, n=16), perimenopausal (PERI, n=17) and postmenopausal (POST n=20), completed a maximal aerobic capacity (VO2 max) ramp test on a cycle ergometer, with expired gases measured throughout. Body composition was assessed by bioelectrical impedance. Resting plasma oestradiol, measured by enzyme linked immunosorbent assay (ELISA), was used to confirm menstrual status. Naturally menstruating premenopausal and perimenopausal women were tested during the early follicular phase (1-7 days after starting menstruation), and postmenopausal or hormonal contraceptive users at earliest convenience. Respiratory exchange ratio (RER), energy expenditure, and fat-carbohydrate oxidation crossover point were evaluated between groups using mixed-effects analysis of variance. RESULTS: Throughout the test, there were differences in energy expenditure between groups (p = 0.02), with the PRE group demonstrating a higher energy expenditure (9.6 ± 3.1 kcal·min-1) than the POST group (8.2 ± 2.7 kcal·min-1) (p<0.05). Body fat mass was different between groups (PRE: 15.6 ± 5.9kg; PERI: 19.8 ± 7.0kg; POST: 22.5 ± 10.1kg, p = 0.05). When normalised for body fat mass, differences in energy expenditure remained (PRE: 0.72 ± 0.22 kcal·min-1·kgBFM; PERI: 0.53 ± 1.9 kcal·min-1·kg·BFM; POST: 0.43 ± 0.14 kcal·min-1·kg·BFM; p<0.01), with PRE energy expenditure greater than POST energy expenditure throughout (p<0.05). There were no differences in the RER (PRE: 0.97 ± 0.13; PERI: 0.96 ± 0.13; POST: 0.96 ± 0.13, p = 0.49) or the exercise intensity at which fat-carbohydrate oxidation crossover occurred between the groups (PRE: 49.6%; PERI: 52.1%, POST: 54.0% of VO2 max, p>0.05). CONCLUSION: Menstrual status did not impact RER during exercise; this is the first study to evidence that menopause has no effect on RER throughout a maximal exercise test. However, in postmenopause energy expenditure may be limited across all intensities during a maximal exercise test suggesting a ceiling effect potentially linked to increased body fat mass. Further research should evaluate the responses to ecologically valid doses of exercise of women across the lifecycle to better understand the changes that occur and the role of oestrogen deficiency in menopause.
Read CV Kate RattleyECSS Paris 2023: CP-PN02
INTRODUCTION: Near-infrared spectroscopy (NIRS) is a non-invasive method to measure and evaluate muscle oxygenation in local tissue (1). It is important to note that possible sex-related differences affect the oxygen transport system depending on exercise intensity (2). However, there is a lack of information on possible sex-related differences in muscle oxygenation responses in other exercise modes such as running. Therefore, the present study aimed to analyze possible sex-related differences in muscle oxygen saturation in trained runners. METHODS: Twelve male and sixteen female trained runners participated in the study. A maximal graded exercise test (GXT) (HP Cosmos Pulsar, HP Cosmos Sports & Medical GMBH, Nussdorf-Traunstein, Germany) was performed. The test started at 8 km·h-1 and 10 km·h-1 for females and males, respectively, and the speed was then increased by 1 km·h-1 every minute until voluntary exhaustion. Two portable NIRS devices (Moxy Monitor) were placed to measure muscle oxygen saturation (SmO2) in the vastus lateralis (VL), at 2/3 of the distance between the line from the anterior spina iliac superior to the lateral side of the patella; and at the most prominent bulge of the medial gastrocnemius (GN). During GTX, respiratory variables were measured using a gas analyzer (CPX Ultima Series MedGraphics). First (VT1) and second (VT2) ventilatory thresholds and maximal oxygen uptake (VO2max) were identified for each participant. A repeated measures ANOVA was used to compare the differences in SmO2 produced at each threshold with sex as an inter-subject factor. RESULTS: There were no significant differences in the interaction threshold (VT1, VT2 and VO2max) × sex (men vs. woman) in SmO2. The mean values in SmO2 of VL and GN were significantly lower (p<0.001) at VT2 and VO2max in comparison with VT1. Woman presented higher values (p<0.001) in SmO2 of VL at VT1 (76.5 vs. 45.5%), VT2 (56.4 vs. 28.0%) and VO2max (41.1 vs. 12.5%) compared to men. The percentage of reduction in SmO2 between VT2 and VO2max were significantly higher (p<0.004) in men (56.0 vs. 27.4%) compared to women. CONCLUSION: The measurement of SmO2 in GN and VL allow to identify a breaking point between the oxygen supply and consumption through NIRS. However, SmO2 had a different behavior in both muscles. Thus, women had higher SmO2 in the three points analyzed in VL but not in GN. Both sexes showed similar patterns of decrease in SmO2 as metabolic demand increases. However, men displayed a strong decline in the VL at VT2 which indicates a better oxygen supply in the active tissues. This fact can be related to a higher muscle vasodilation capacity in females that leads to a redistribution of oxygen to the active tissues and to a higher estrogen concentration. REFERENCES 1. Kitada T, Machida S, Naito H. BMJ Open Sport Exerc Med. 2015;1(1):e000062. 2. Sendra-Perez C, Priego-Quesada JI, Salvador-Palmer R, Murias JM, Encarnacion-Martinez A. J Appl Physiol (1985). 2023;135(5):1092-101.
Read CV Sergio Rodríguez-BarberoECSS Paris 2023: CP-PN02