Abstract
The aim of the current study was to investigate the effect of a single session of prolonged tendon vibration combined with low submaximal isometric contraction on maximal motor performance. Thirty-two young sedentary adults were assigned into two groups that differed based on the knee angle tested: 90° or 150° (180° = full knee extension). Participants performed two fatigue-inducing exercise protocols: one with three 10 min submaximal (10% of maximal voluntary contraction) knee extensor contractions and patellar tendon vibration (80 Hz) another with submaximal knee extensor contractions only. Before and after each fatigue protocol, maximal voluntary isometric contractions (MVC), voluntary activation level (assessed by the twitch interpolation technique), peak-to-peak amplitude of maximum compound action potentials of vastus medialis and vastus lateralis (assessed by electromyography with the use of electrical nerve stimulation), peak twitch amplitude and peak doublet force were measured. The knee extensor fatigue was significantly (P<0.05) greater in the 90° knee angle group (-20.6% MVC force, P<0.05) than the 150° knee angle group (-8.3% MVC force, P = 0.062). Both peripheral and central alterations could explain the reduction in MVC force at 90° knee angle. However, tendon vibration added to isometric contraction did not exacerbate the reduction in MVC force. These results clearly demonstrate that acute infrapatellar tendon vibration using a commercial apparatus operating at optimal conditions (i.e. contracted and stretched muscle) does not appear to induce knee extensor neuromuscular fatigue in young sedentary subjects.
Highlights
Over the past two decades, the effects of prolonged tendon vibration on maximal motor performance have been widely investigated
The aim of this study was to investigate the acute effects of an exercise, combining prolonged tendon vibration and weak submaximal isometric contraction, on maximal force production at two different knee angles
Because muscle length influences the effect of tendon vibration on neuromuscular function [40], we investigated whether knee angle may change the acute effect of the Effect of tendon vibration on neuromuscular performance combined exercise
Summary
Over the past two decades, the effects of prolonged tendon vibration on maximal motor performance have been widely investigated. It has been reported that peripheral mechanisms are rarely altered [3,6,7,8,13,14,15,16], suggesting that the decrease in MVC force is mainly explained by neural alterations In this context, previous studies showed an attenuation of Ia afferent function [1,2,5,7,8], supported by reductions in spinal loop excitability, as evidence by H-reflex measurement [13,14]. Recent investigations did not reveal a significant effect of tendon vibration on maximal motor performance for muscle groups crossing the ankle or the knee joints [13,14,15,16]. Experimental parameters such as the vibration frequency used [1,16] have been examined in the literature to maximize fatigue effect following prolonged tendon/ muscle vibration, other factors need to be explored such as muscle activity (i.e. contraction) or joint angle (i.e. muscle length) during vibration
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