Abstract
Leg cycling is one of the most common modes of exercise used in athletics and rehabilitation. This study used a novel cycling setting to elucidate the mechanisms, central vs. peripheral fatigue induced by different resistance with equivalent works (watt∗min). Twelve male adults received low and relatively high resistance cycling fatigue tests until exhausted (RPE > 18) in 2 weeks. The maximal voluntary contraction, voluntary activation level, and twitch forces were measured immediately before and after cycling to calculate General (GFI), central (CFI), and peripheral (PFI) fatigue indices of knee extensors, respectively. The results showed that the CFI (high: 92.26 ± 8.67%, low: 78.32 ± 11.77%, p = 0.004) and PFI (high: 73.76 ± 17.32%, low: 89.63 ± 11.01%, p < 0.017) were specific to the resistance of fatigue protocol. The GFI is influenced by the resistance of cycling to support the equivalent dosage. This study concluded that the mechanism of fatigue would be influenced by the resistance of fatigue protocol although the total works had been controlled.
Highlights
Leg cycling is one of the most common modes of exercise used in athletics and rehabilitation to evaluate or promote cardiopulmonary endurance, increase lower extremity muscle strength and endurance, and maintain lower extremity range of motion (Kubukeli et al, 2002; Fang et al, 2015; Wei et al, 2018)
Upon reaching fatigue at low resistance, the maximal voluntary contractions (MVCs) decreased from 39.26 ± 9.63 kg to 35.24 ± 8.61 kg
Upon reaching fatigue at relatively high resistance, the MVC decreased from 38.05 ± 8.35 kg to 33.07 ± 10.58 kg (Figure 4A)
Summary
Leg cycling is one of the most common modes of exercise used in athletics and rehabilitation to evaluate or promote cardiopulmonary endurance, increase lower extremity muscle strength and endurance, and maintain lower extremity range of motion (Kubukeli et al, 2002; Fang et al, 2015; Wei et al, 2018). Leg cycling exercise interventions in individuals with motor dysfunction have shown that the effects of leg cycling exercise training can be translated into improved postural control in standing and better function during daily activities involving the lower extremities, such as walking speed and endurance (Katz-Leurer et al, 2006; Yang et al, 2014). It is commonly used in athlete training for improving physical fitness (Jones et al, 2015; Paquette et al, 2017; Androulakis-Korakakis et al, 2018). Researchers had put great efforts to elucidate the mechanisms and the sources of fatigue following exercise (Gandevia, 2001; Lepers et al, 2002; Amann et al, 2006, 2008; Boyas and Guevel, 2011; Millet, 2011; Elmer et al, 2013; Jubeau et al, 2014; Thomas et al, 2015, 2016; Tomazin et al, 2017; Ansdell et al, 2018)
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