The influence of moderate hypobaric hypoxia on power oriented resistance training

Resumen

Intermittent hypoxic resistance training (IHRT) may help to maximize the neural and structural adaptations following resistance training, although conflicting evidence is available. Previous investigations have reported contradicting results as regards the acute and chronic adaptations to hypertrophy-oriented IHRT. However, the potential effects of power-oriented resistance training remain unexplored, particularly under conditions of hypobaric hypoxia. Therefore, the main goal of this thesis was to examine the acute and chronic influence of intermittent exposure to moderate hypobaric hypoxia on the functional and neuromuscular responses to power-oriented resistance training. Five separate research experiments were carried out to 1) refine the training and testing tools to assess strength performance and training adaptations and 2) investigate the specific influence of intermittent moderate altitude exposure. The first preliminary study (Section 3.1) provided evidence regarding the importance of training intensity in the short-term training adaptations. Three weeks of power training including cluster set configurations seem more efficient at inducing velocity and power adaptations, specific to the training load. A second preliminary study (Section 3.2) examined performance and surface electromyography (EMG) changes during a power training protocol comprising continuous or clustered set configurations. Progressive changes in the EMG signal power spectrum were observed across repetitions in both set configurations, showing unclear acute effects of cluster sets on EMG parameters, despite maximizing power output. A crossectional investigation (Section 3.3) was then carried out to explore relationships between the force-velocity (FV) profile, the isometric muscle torque performance, quadriceps voluntary activation and muscle architecture during a unilateral knee-extension task in 43 participants. These results provided evidence for the strong relationship between the knee extensors maximal isometric strength and their morphological architecture with maximal strength estimated from a CMJ FV profile test. Two investigations conducted at moderate altitude explored 1) the influence of hypoxia on lower-body strength performance and EMG activation during a power-oriented resistance training session (Section 3.4) and 2) the influence of moderate altitude on the functional, neural and muscle architecture responses of the quadriceps muscles following an 8-week power-oriented IHRT intervention (Section 3.5). The main results suggest that, while similar maximal isometric strength and net CMJ mechanical performance during resistance training occur at moderate hypobaric hypoxia, the perceptual and performance fatigability responses may be affected in a load-specific manner. Similar rates of change across efforts are nonetheless observed in the interference EMG signal, highlighting the complex nature of fatigue development and our ability to assess it during dynamic resistance training movements. Moreover, in an active but non-elite population, the short-term adaptive responses to power-oriented resistance training seem to be of similar magnitude at a functional and neuromuscular level in both altitude levels explored.