Comparison of an intermittent and continuous forearm muscles fatigue protocol with motorcycle riders and control group

Abstract Motorcycle races' long duration justify the study of forearm muscles fatigue, especially knowing the frequently associated forearm discomfort pathology. Moreover, while continuous fatigue protocols yield unequivocal results, EMG outcomes from an intermittent protocol are quite controversial. This study examined the forearm muscle fatigue patterns produced during these two protocols, comparing riders with a control group, and relating maximal voluntary contraction with EMG parameters (amplitude – NRMS and median frequency – NMF) of both protocols to the forearm discomfort among motorcycle riders. Twenty riders and 39 controls performed in separate days both protocols simulating the braking gesture and posture of a rider. EMG of flexor digitorum superficialis (FS) and carpi radialis (CR) were monitored. CR revealed more differences among protocols and groups compared to FS. The greater CR activation in riders could be interpreted as a neuromotor strategy to improve braking precision. When FS fatigue increased, the control group progressively shift toward a bigger CR activation, adopting an intermuscular activation pattern closer to riders. Despite the absence of NMF decrement throughout the intermittent protocol, which suggest that we should have shorten the recovery times from the actual 1min, the superior number of rounds performed by the riders proved that this protocol discriminates better riders against controls and is more related to forearm discomfort.