ECSS Paris 2023: OP-PN18
INTRODUCTION: Energy availability is a key determinant of physiological function and athletic performance (1). Despite the established evidence linking long-term low energy availability to compromised health (2), short-term low term energy intake (LEI) effects on cardiorespiratory and metabolic responses in female remain unclear. Therefore, this study aimed to investigate the effects of LEI on cardiorespiratory variables in exercising females under controlled nutritional interventions. METHODS: Nine naturally menstruating females with confirmed luteinizing hormone peak completed a treadmill interval protocol consisting of 8x3-min at 95% of the ventilatory threshold (VT2) with 90 s of active rest on two occasions. One occasion after six days of LEI [35 kcal·kg· fat-free mass (FFM)-1] and the other one under control conditions (60 kcal·kg· FFM-1). Oxygen consumption (VO₂) and relative to body weight (VO₂/kg), carbon dioxide production (VCO₂), ventilation (VE) and respiratory exchange ratio (RER) were continuously measured (JAEGER® Vyntus CPX) along heart rate (HR, Polar H10 device). RESULTS: A significant main effect of condition was observed for VO2/kg (p<0.001; LEI: 32.5±12.2 vs control: 30.9±12.2 ml/kg/min), RER (p<0.001; LEI: 0.9±0.08 vs control: 0.95±0.07), V̇E (p=0.013; LEI: 56.3±20.6 vs control: 54.5±20.3 l/min), and HR (p=0.004; LEI: 154±31 vs control: 151±30 bpm), with higher VO2/kg and HR values, alongside lower RER and V̇E values, following the LEI compared with the control condition. No significant differences were observed for VO2 or V̇CO2 (p > 0.05) nor weight (p=0.058). CONCLUSION: Short-term LEI may alter cardiorespiratory and metabolic responses to exercise in exercising females. The increase in VO2/kg with no increase in absolute VO2, may reflect the statistical trend to a reduction in body mass associated with LEI (3) rather than a real enhancement in aerobic capacity. In addition, higher HR values may reflect changes in autonomic control that can impact HR responses during exercise stress associated with energy availability (4). Lower RER values during LEI suggest a shift toward greater reliance on fat oxidation due to the reduced carbohydrate intake, which may reinforce the effects of short-term. Furthermore, lower VE values may indicate an alteration in ventilatory function despite cardiovascular strain as a compensatory response to maintain exercise response under LEI conditions (5). References 1.Thomas, D.T. et al. (2016). J Acad Nutr Diet. doi:10.1016/j.jand.2015.12.006 2.Mountjoy, M. et al (2023). Br J Sports Med. doi:10.1136/bjsports-2023-106994 3.Burke, L.M. et al. (2023). Med Sci Sports Exerc. doi:10.1249/MSS.0000000000003074 4.Gallant, T.L. et al. (2024). Sports Med. doi:10.1007/s40279-024-02036-6 5.Oxfeldt, M. et al. (2023). Med Sci Sports Exerc. doi:10.1249/01.mss.0000987148.52126.c2
Read CV Mónica Torres-SantiagoECSS Paris 2023: OP-PN18
INTRODUCTION: Physiological determinants of endurance performance, such as exercise thresholds, have been shown to deteriorate during prolonged exercise, which forms the basis of the physiological resilience concept. However, underpinnings mechanisms are still unclear, and one candidate for this alteration could be exercise-induced muscle damage (EIMD). EIMD occurs when performing an unaccustomed exercise, particularly when it is associated with eccentric contractions, like in downhill running (DR). This study investigated the effects of prolonged DR and cycling on the power outputs (PO) at the gas exchange threshold (GET) and at the respiratory compensation point (RCP). METHODS: Twelve healthy subjects (9 males, VO2peak: 47.6±7.8 mL/min/kg) performed one maximal cycling ramp incremental (RI) test to assess baseline (BSL) PO at the GET and at the RCP and one submaximal DR RI test (-15% slope) to determine the speed at the GET. Maximal RI in cycling were repeated on three occasions: (i) after 45 min of cycling at 80% of PO at the GET (C), (ii) after 45 min of DR at 80% of speed at the GET (R), (iii) 48h after R (R48H). Knee extensors maximal isometric voluntary torque (MVT) and the torque evoked by potentiated doublet of electrical stimulation of the femoral nerve at 10 (Db10) and 100Hz (Db100) were measured pre and 20min post fatiguing exercise in cycling and DR and at R48H, all prior to the ramp. A linear mixed-effects model combined with ANOVA was used for statistical analysis. Results are presented as estimated marginal means [95% CI]. RESULTS: There was no effect of condition for PO at the GET (BSL: 167 [138-197] vs C: 162 [132-192] vs R: 165 [135-196] vs R48H: 164 [134-194] W, p=0.908) and at the RCP (250 [209-291] vs 242 [201-283] vs 245 [204-286] vs 247 [206-289] W, p=0.696). There was a significant decrease in MVT (301 [252-351] vs 280 [230-329], p<0.001) and Db10/Db100 (0.953 [0.911-0.996] vs 0.848 [0.806-0.891], p<0.001), with no effect of condition, nor time x condition interaction for both variables. There was no difference in MVT (299 [249-349] vs 310 [260-361], p=0.5) and Db10/Db100 (0.95 [0.9-1] vs 0.98 [0.93-1.03], p=0.749) between pre-R and R48H. CONCLUSION: There was no effect of neither fatiguing exercises on the PO at the GET and at the RCP. Nevertheless, the similar changes in MVT and Db10/Db100 observed after the cycling exercise suggest that they were induced by the metabolic load that was equivalent between conditions, instead of being the consequence of EIMD. Thus, despite the abundant literature showing that prolonged DR results in EIMD, we conclude that the metabolic and mechanical loads were insufficient to significantly reduce the PO at the GET and at the RCP and that 45 min of DR at -15% slope in the moderate intensity domain does not alter EIMD markers.
Read CV Thomas MONOTECSS Paris 2023: OP-PN18
INTRODUCTION: Substantial hemolysis has been suggested during mountain ultramarathons (MUM), primarily due to repeated ground impact and muscle contractions. However, new findings indicate that this hemolysis is insufficient to reduce total hemoglobin mass (Hbmass). Instead, recents results suggest an accelered red blood cell (RBC) turnover. Indeed, although not reaching statistical significance, increases in Hbmass of +12 g (1.4%) and +31 g (3.9%) have been reported following 170-km and 330-km MUMs, respectively. Consequently, one may speculate that Hbmass could increase significantly with increasing MUM distances. Finally, plasma volume (PV) and related total blood volume (BV) expansion has been shown to be proportional to the distance, with no evidence of a physiological plateau to date. The aim of the present study was to investigate changes in circulating blood volumes and erythropoietic variables across a 700-km MUM. METHODS: Eighteen participants (of 30) completed the SwissPeaks 2025 race (685 km; 48'020 m of cumulative elevation gain) with an average finisher time of 195 ± 21 h. Participants were tested four times; i.e., before (PRE), after 90 km, 300 km, and immediately after the finish (POST). At each time point, Hbmass, BV, PV, and red blood cell volume (RBCV) were measured using an optimized carbon monoxide rebreathing technique (Detalo Performance). In addition, venous blood samples were collected and analyzed for complete blood count and reticulocyte parameters (Sysmex XN-1000). RESULTS: Although unaffected during the first part of the race, significant increases in Hbmass (+32 ± 26 g [3.6%], p < 0.001) and RBCV (+97 ± 85 mL [3.7%], p < 0.001) were observed at POST. Increases in PV and BV were already evident after 90 km (+275 ± 362 mL [7.5%] and +271 ± 362 mL [4.3%], respectively; p = 0.001), further expanding after 300 km (+657 ± 388 mL [18.2%] and +685 ± 397 mL [11%], respectively; p < 0.001) before stabilizing toward the end of the race. Immature reticulocyte fraction (IRF) increased after 300 km (+4.5 ± 11.4%, p = 0.02), while reticulocyte percentage (RET%) rose progressively, reaching 1.3 ± 0.5% (p = 0.03) at km 300 and 1.6 ± 0.5% (p = 0.001) at POST. Finally, mean corpuscular volume (MCV) decreased at km 90 (–0.86 ± 0.80 fL [0.98%], p < 0.001) but gradually increased thereafter, together with red cell distribution width - standard deviation (RDW-SD). Both MCV (+1.09 ± 0.88 fL [1.23%], p < 0.001) and RDW-SD (+2.3 ± 1.6%, p < 0.001) exceeding PRE values at POST. CONCLUSION: The hypothesis of increases in Hbmass and RBCV after the race was confirmed. These findings are supported by the sequential rise in IRF and RET%, indicating stimulated erythropoiesis. Similarly, the post-race increases in MCV and RDW-SD reflect a larger average RBC size and greater heterogeneity, likely due to an elevated proportion of young RBC. Finally, results suggest that a physiological plateau in PV expansion during MUMs is reached after approximately 300 km.
Read CV Bastien KrummECSS Paris 2023: OP-PN18