ECSS Paris 2023: OP-PN34
INTRODUCTION: The relationship between cycling power output and time to exhaustion (TTE) displays a curvilinear form that can be linearised by employing the logarithm of TTE. This relationship persists even for exhaustive intermittent exercise, wherein high- and low-intensity intervals of fixed power and duration are alternated. While training status, body dimensions, and sex influence the power outputs someone can generate, seemingly comparable cyclists can still manifest considerable inter-individual variability in TTEs. This study explored which factors might contribute to longer TTEs during high-intensity interval training (HIIT). METHODS: The dataset of Bossi et al. (2023) was reutilised. Sixteen male and two female competitive cyclists (age: 38 ± 11 years, maximal oxygen uptake (V̇O2max): 54 ± 9 ml·kg-1·min-1) performed an incremental test, two 3-min all-out tests, and two 20-min time trials to establish physiological and performance benchmarks after a familiarisation (visits 1 and 2). Then, in randomised order, participants performed four HIIT sessions to exhaustion at power outputs associated with different intensity prescription methods (visits 3 to 6). HIIT sessions consisted of 4-min work intervals interspersed with 2-min active recoveries. The natural logarithm of TTE in seconds was modelled using linear mixed models, with participant as a random effect, and HIIT power output, age, height, body mass, the maximal scores in the incremental test (V̇O2max, power output, heart rate, respiratory exchange ratio, respiratory rate, rating of perceived exertion, blood lactate concentration), the power outputs associated with the gas exchange threshold and respiratory compensation point, critical power, work capacity above critical power, time trial mean power output, and estimated vastus lateralis adipose tissue thickness as fixed effects. The best model was selected based on Akaike information criteria. Significance was set at P ≤ 0.05. RESULTS: The best model revealed that HIIT power output, V̇O2max, and maximal respiratory exchange ratio (RERmax) are all determinants of TTE, with the first two emerging as primary factors. Specifically, with an intercept of 11.309 (SE = 3.292), a unit increase in power output reduces the log transformed TTE by 0.032 (SE = 0.003). Conversely, a unit increase in V̇O2max extends the log transformed TTE by 2.267 (SE = 0.277). A decimal unit increase in RERmax reduces the log transformed TTE by 0.277 (SE = 2.621). The model indicated considerable inter-individual differences, with a SD of 0.460 for the intercept. The SD for the residual variability was estimated as 0.318. CONCLUSION: Besides the expected effect of the power output target for HIIT, it seems that individuals with higher V̇O2max, attained with lower RERmax, are more likely to produce longer TTEs. A complex interplay of attributes, possibly involving unexplored factors, complicates the individualisation of HIIT prescription. REFERENCE: Bossi et al. (2023) Eur J Appl Physiol 123, 1655–1670
Read CV Arthur Henrique BossiECSS Paris 2023: OP-PN34
INTRODUCTION: Transcranial direct current stimulation (tDCS) has emerged as a minimally invasive form of cortical stimulation, with exciting potential for exercise performance. While some studies have confirmed the apparent ergogenicity of tDCS during continuous, large muscle-mass exercise, not all findings are consistent. The variable results between tDCS studies may be attributed, at least in part, to differences in exercise intensity. We, therefore, investigated the effects of acute tDCS on exercise tolerance and the physiological responses to heavy- and severe-intensity exercise METHODS: Twelve healthy, recreationally active men (mean age ± SD = 25 ± 2 yr, VO2peak 50 ± 8 ml/kg/min) volunteered to participate in this study. All participants were required to report to the laboratory on five separate occasions. On Day 1, they performed a ramp incremental exercise test on an electronically braked cycle ergometer to determine gas exchange threshold (GET), VO2peak, and peak power output (PPO). On Days 2-5, participants received, in a random and crossover order, 20 minutes of brain stimulation of either sham tDCS or anodal tDCS (current intensity: 2 mA) before either heavy- or severe-intensity cycling exercise. Pulmonary exchange and ventilation data, NIRS-derived muscle oxygenation and hemodynamics responses, and surface EMG signals were recorded throughout the exercise bouts. Ratings of perceived exertion (RPE) were also assessed every 2 min in each exercise bout RESULTS: No significant effects of brain stimulation on exercise tolerance were observed (261 ± 56 sec and 258 ± 59 sec for sham tDCS and anodal tDCS, respectively; P > 0.05). Anodal tDCS did not induce significant changes in pulmonary gas exchange and ventilation parameters, NIRS-derived muscle oxygenation and hemodynamics responses, or muscle fibre conduction velocity during heavy- and severe-intensity exercise compared to sham tDCS (P > 0.05). Similarly, RPE did not significantly differ between the brain stimulation conditions at any time in both exercise intensities (P > 0.05) CONCLUSION: Our findings indicate that acute brain stimulation with anodal tDCS applied over the primary motor cortex (M1) does not appreciably alter physiological responses to heavy- and severe-intensity exercise or improve exercise tolerance in healthy, recreationally active men. These results support the notion that this simple, minimally invasive neuromodulatory technique may not be effective during continuous, high-intensity, large muscle-mass exercise
Read CV Stefano Dell AnnaECSS Paris 2023: OP-PN34
INTRODUCTION: Sleep is a critical component of athletic performance and recovery. This study investigates the effects of different types of high-intensity exercise on sleep parameters in youth speed skaters. METHODS: 18 male youth speed skaters underwent aerobic capacity testing, Wingate testing, and interval training. All subjects completed 3 types of exercise including Aerobic Capacity Test, Wingate test, and Interval Training, one week between each type of exercise. Relative maximum power, relative average power, and heart rate were recorded during each type of exercise, fingertip blood was collected at the immediate end of exercise for blood lactate concentration analysis using an EKF portable blood lactate meter(EKF Lacate-Scout, EKF, Germany) and subjects were asked about their level of fatigue by Borg (6-20) Rating of Perceived Exertion (RPE) scale.The Firstbeat Bodyguard 3 sleep monitor (Firstbeat Bodyguard 3, Finland)was used to monitor the sleep quality of the subjects on the nights without any training and following each type of exercise. 7 parameters were selected, including: Sleep duration, Relaxation Time, Stress time, Average HR (Average Heart Rate), Average RespR (Average Respiratory Rate), as well as heart rate variability indicators RMSSD, LF/HF. RESULTS: The maximum and average power achieved in the Wingate Test are significantly higher than those in the Aerobic Capacity Test(p<0.01) and Interval Training (p<0.01). Among the three types of training, post-Interval Training resulted in the highest blood lactate concentration, significantly higher than the Aerobic Capacity Test(p<0.01) and Wingate Test(p<0.01). There was no significant difference in the maximum heart rate of the subjects among the three types of training (p>0.05), all exceeding 90% of the HRmax. Additionally, there was no significant difference in the Rating of Perceived Exertion (RPE) among the three types of training (p>0.05).The study results revealed that Wingate testing and interval training led to reduced sleep duration, increased stress duration, decreased RMSSD, and elevated LF/HF(p<0.01). Conversely, aerobic capacity testing showed no significant effect on sleep(p>0.05). Interval training had a more profound effect on sleep parameters than Aerobic Capacity Test(p<0.01) and the Wingate Test(p<0.01). CONCLUSION: In conclusion, high-intensity anaerobic exercise has a more profound effect on athlete sleep, primarily resulting in decreased sleep duration, increased stress duration, decreased RMSSD, and elevated LF/HF .
Read CV JUNPENG FENGECSS Paris 2023: OP-PN34