PHYSIOLOGICAL, PERFORMANCE, AND FATIGABILITY THRESHOLDS DURING AEROBIC ECCENTRIC EXERCISE

Abstract

Due to unique mechanisms of force production and motor unit recruitment during eccentric contractions, exercises composed mainly by this type of contraction allow the accumulation of large amounts of mechanical work with low metabolic cost, cardiorespiratory burden, and perceived exertion. These characteristics make eccentric exercise modalities (especially aerobic eccentric exercise - AEE) viable alternatives for training healthy young and elderly individuals, as well as for the treatment/rehabilitation of patients with cardiorespiratory diseases. Evidence suggests that periods of AEE training can induce both increases in strength and muscle mass and improvements in aerobic fitness and body composition. However, there is significant variability in the chronic responses to this type of modality - possibly due to the lack of physiological and performance parameters that guide the prescription of the AEE. Conventional (i.e., concentric) exercises are commonly prescribed based on maximal intensity achieved in incremental testing or maximum repetition and/or on submaximal physiological or performance thresholds. In this sense, little is known about the maximum capacity for eccentric exercise or the existence of submaximal thresholds that can guide the prescription of AEE modalities. Therefore, this research project aims to: 1) investigate the factors that limit the maximum capacity of eccentric cycling (i.e., an AEE modality) and identify possible submaximal physiological thresholds during incremental tests performed until exhaustion; 2) investigate the power-duration relationship of eccentric cycling and the acute physiological responses to constant-load bouts performed at different relative intensities; 3) to investigate the torque-duration relationship of submaximal eccentric knee extension exercise and the development of neuromuscular fatigue during constant-load bouts performed at different relative intensities. The three proposed experiments will be conducted collaboratively at São Paulo State University and Edith Cowan University (Australia).