Isometric knee extensor fatigue following a Wingate test: peripheral and central mechanisms

Abstract

Central and peripheral fatigue have been explored during and after running or cycling exercises. However, the fatigue mechanisms associated with a short maximal cycling exercise (30 s Wingate test) have not been investigated. In this study, 10 volunteer subjects performed several isometric voluntary contractions using the leg muscle extensors before and after two bouts of cycling at 25% of maximal power output and two bouts of Wingate tests. Transcranial magnetic stimulation (TMS) and electrical motor nerve stimulation (NM) were applied at rest and during the voluntary contractions. Maximal voluntary contraction (MVC), voluntary activation (VA), twitch amplitude evoked by electrical nerve stimulation, M wave and motor potential evoked by TMS (MEP) were recorded. MVC, VA and twitch amplitude evoked at rest by NM decreased significantly after the first and second Wingate tests, indicating central and peripheral fatigue. MVC and VA, but not the twitch amplitude evoked by NM, recovered before the second Wingate test. These results suggest that the Wingate test results in a decrease in MVC associated with peripheral and central fatigue. While the peripheral fatigue is associated with an intramuscular impairment, the central fatigue seems to be the main reason for the Wingate test-induced impairment of MVC.

Resting and active motor thresholds versus stimulus–response curves to determine transcranial magnetic stimulation intensity in quadriceps femoris

“…Studies determining stimulus intensity during contractions have often used normalized MEP amplitude or area of a given size as criteria [7,8,19,20]. For example, Sidhu et al [20] selected an intensity that produced the largest RF MEP with the stipulations that this must be at least 50% Mmax and that antagonist BF MEP amplitude be less than 10% raw RF MEP amplitude.…”

“…This suggests that one muscle could be used as a surrogate for other quadriceps muscles. RF alone has frequently been used to determine quadriceps stimulus intensity [6,8,19,20]. When RF is normalized, MEP amplitude is larger than for either VL or VM due to consistently smaller Mmax in the RF and little differences in raw MEP amplitude.…”

“…Another common method is AMT (the lowest intensity necessary to elicit detectable MEPs or MEPs of a pre-determined amplitude in at least one half of a given number of stimuli during weak voluntary contraction) [10,12,16-18]. More recently, numerous studies have selected a stimulus intensity to evoke MEP responses of a certain size in the target muscle during voluntary contraction [2,6-8,19,20]. Some studies are unclear about the intensity chosen for TMS [21] or whether intensity determination was performed with the muscle in the relaxed or contracted state [22].…”

Effects of Locomotor Muscle Fatigue on Joint-Specific Power Production during Cycling

“…For example, all of the joint-specific fatigue indices from the 30-s maximal cycling data are greater than the pre-to post-TT values from the present study: ankle plantarflexion (63% vs 43%), knee extension (52% vs 12%), knee flexion (55% vs 52%), and hip extension (45% vs 28%). Such a considerable difference could be related to total work and power produced during the fatiguing trial, pedaling rate (90 vs 120 rpm), disturbances in the metabolic milieu within the muscle, peripheral fatigue, and/or central fatigue (14,21). These comparisons demonstrate that joint-specific power loss is highly dependent on the duration and intensity of the cycling task as well as the methods used to quantify fatigue (i.e., changes in power within trial vs preexercise-to-postexercise change).…”

Pacing Strategy, Muscle Fatigue, and Technique in 1500-m Speed-Skating and Cycling Time Trials

“…As some recovery is likely, muscle fatigue mechanisms could thus not be estimated to their full extent 25,28 . Speculation about the recovery from central and peripheral fatigue is difficult as recovery of muscle fatigue is task dependent and no data comparing cycling and speed skating is present at the moment.…”