Abstract
The effect of muscle fatigue on rate of force development (RFD) is usually assessed during tasks that require participants to reach as quickly as possible maximal or near-maximal force. However, endurance sports require athletes to quickly produce force of submaximal, rather than maximal, amplitudes. Thus, this study investigated the effect of muscle fatigue induced by long-distance running on the capacity to quickly produce submaximal levels of force. Twenty-one male amateur runners were evaluated before and shortly after a half-marathon race. Knee extensors force was recorded under maximal voluntary and electrically evoked contractions. Moreover, a series of ballistic contractions at different submaximal amplitudes (from 20 to 100% of maximal voluntary force) was obtained, by asking the participants to reach submaximal forces as fast as possible. The RFD was calculated for each contraction. After the race, maximal voluntary activation, resting doublet twitch, maximal force, and RFD during maximal contraction decreased (-12, -12, -21, and -19%, respectively, all P-values < 0.0001). Nevertheless, the RFD values measured during ballistic contractions up to 60% of maximal force were unaffected (all P-values > 0.4). Long-distance running impaired the capacity to quickly produce force in ballistic contractions of maximal, but not of submaximal, amplitudes. Overall, these findings suggest that central and peripheral fatigue do not affect the quickness to which muscle contracts across a wide range of submaximal forces. This is a relevant finding for running and other daily life activities that rely on the production of rapid submaximal contractions rather than maximal force levels.
Highlights
Muscle fatigue can be defined as an exercise-induced decreased capacity to generate maximal force (Gandevia, 2001)
Out of the 23 initially recruited participants, two individuals did not tolerate the peripheral nerve stimulation, data are reported for 21 participants
This is in line with our previous studies where we found a moderate decrease in maximal force after half-marathons performed in similar experimental conditions (Boccia et al, 2017a,b, 2018)
Summary
Muscle fatigue can be defined as an exercise-induced decreased capacity to generate maximal force (Gandevia, 2001). Measuring reductions in maximal voluntary contraction force (MVCF) is considered as the most valid and widespread approach to measure muscle fatigue (Millet and Lepers, 2004; Place et al, 2010). It is a sensitive and reliable procedure, which is easy to administer in a variety of research settings (Wilson and Murphy, 1996). Under the time-restricted conditions of short muscle actions, the ability to rapidly produce force is considered functionally more important than maximal force (Maffiuletti et al, 2016; Rodriguez-Rosell et al, 2017). It was shown that the capacity to maintain a rapid force production is important in fatigued states, even though this aspect has received little attention in the literature so far (Girard et al, 2015; Morel et al, 2015)
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