Author(s): CHAMBION-DIAZ, M., PIALOUX, V., BILLAUT, F. , Institution: CLAUDE BERNARD UNIVERSITY LYON 1, Country: FRANCE, Abstract-ID: 745

INTRODUCTION:
The AlterG treadmill allows weight reduction during running, which lowers mechanical stress. This tool therefore has great potential applications in return from injuries and to maximize training benefits under lower mechanical stress in healthy athletes. However, there is no strong evidence regarding the beneficial effect of AlterG running on athlete’s physical performance. Moreover, reducing mechanical load might potentially decrease physiological stress and subsequent adaptations. Hypoxia is well known to increase metabolic stress and may thus offer a countermeasure to optimize the benefits from weightless running in varied training scenarios. To date, there is no study examining physiological responses to such training strategy. The aim of this study is to verify the feasibility of combining running with body weight reduction and hypoxia during high-intensity interval exercise, and characterize the psychophysiological responses to such exercise-environment combination.
METHODS:
Twenty-two participants volunteered for the project, but only three (2 men, 1 woman, age:24.6 years, height:168.3cm, weight:66.7kg, VO2max:62ml/min/kg) completed the protocol to date. Participants completed a high-intensity interval training (HIIT) session on an AlterG treadmill in the following 5 experimental conditions in randomized order: normoxia at 100% body weight (BW); normoxia at 80% BW; normoxia at 60% BW; hypoxia (FIO2 = 14%) at 80% BW; hypoxia at 60% BW. The HIIT session included 3 sets of 8 repetitions of 30 seconds of effort performed at 110% of the maximum aerobic speed, interspersed with 30 seconds of passive recovery. During the session, heart rate (HR), pulse arterial O2 saturation (SaO2), muscle deoxyhemoglobin (HHb) concentration and rate of perceived exertion (RPE) were continuously recorded. Blood lactate concentration was measured post-session.
RESULTS:
Weight reduction by AlterG increased SaO2 by 3% and reduced both HR by 27bpm and RPE by 2.4 points compared to control (p<0.05). When hypoxia was added, SaO2 was reduced by 9 to 13% compared to the 3 other conditions in normoxia with varied weights. HR was lower in all conditions compared to control (p<0.05). RPE was higher in hypoxia by 1 point compared to the 2 other conditions in normoxia and weight reduction (p<0.05). Hypoxia increased [HHb] by 21 mmol compared to the 2 other conditions in normoxia and weight reduction (p<0.05). There was no significant difference in [lactate] at the end of the effort across conditions (p=0.08).
CONCLUSION:
These preliminary data suggest that mechanical load and hypoxia differently modulate psychophysiological responses to high-intensity exercise in a different way. Further analyses will allow us to confirm these initial observations and to ascertain whether biological sex mediates these phenotypic responses.