Muscle Contractile Properties Measured at Submaximal Electrical Amplitudes and Not at Supramaximal Amplitudes Are Associated with Repeated Sprint Performance and Fatigue Markers

Abstract

Background: The present study analyzes the associations between the muscle contractile properties (MCP) measured at different neuromuscular electrical stimulation amplitudes (NMESa) and the performance or transient fatigue after a bout of repeated sprints. Methods: Seventeen physically active male subjects performed six repeated sprints of 30 m with 30 s of passive recovery. Capillary blood creatine kinase (CK) concentration, knee extension or flexion isometric peak torque, tensiomyography, and repeated sprint performance were assessed. Results: Muscle displacement and contraction time were different in relation to the NMESa used in the rectus femoris and biceps femoris muscles. At rest, significant (p < 0.05) associations were found between muscle displacement and the loss of time in the repeated sprints (sprint performance) at 20 or 40 mA in the rectus femoris. At post +24 h or +48 h, the highest significant associations were found between the muscle displacement or the contraction time and CK or peak torques also at submaximal amplitudes (20 mA). The NMESa which elicits the peak muscle displacement showed lack of practical significance. Conclusion: Although MCP are typically assessed in tensiomyography using the NMESa that elicit peak muscle displacement, a submaximal NMESa may have a higher potential practical application to assess neuromuscular fatigue in response to repeated sprints.

The Effect of Music Tempo on Fatigue Perception at Different Exercise Intensities

“…The reasons for this result in this study may be twofold. (1) The experimental test time was short, and the runners reached the specified value of subjective fatigue in a short period of time, during which the local muscle tissue continuously recruited fast muscle fibers to participate in the exercise so that the muscle firing frequency increased, and the neural excitability continued during the running process [ 59 , 60 ]. (2) The energy consumption during muscle contraction during running did not exceed the energy recovery during relaxation, and the lactic acid accumulation was not significant, so the driving strategy of the central nervous system for the muscles and the conduction speed of the muscle fibers were not affected [ 61 ].…”