Response of Electromyographic Variables during Incremental and Fatiguing Cycling

Abstract

During dynamic cycle exercise, EMG variables are reliable and increase with power output. During fatiguing exercise, EMG variables may be sensitive to learning effects in the execution of the task. MFCV and RMS are correlated with varying power output in the nonfatigued muscle, but not during the development of fatigue.

Muscle fibre conduction velocity during a 30-s Wingate anaerobic test

“…57.6% reduction in peak power during the WAnT cannot be fully attributed to the decrease in MFCV, which declined 26.8%. Similar links between MFCV and power output have been reported previously for incremental aerobic activities (Macdonald et al, 2008). However, as MFCV is generally higher in type II fibres, the change in MFCV would reflect a change in the muscle fibre recruitment.…”

Non-invasive assessment of muscle fiber conduction velocity during an incremental maximal cycling test

“…In fact, among the physiological meanings than can be attributed to the MFCV, its role as a tool to study the MUs activation strategy has been demonstrated both during static and dynamic exercises (Farina et al, 2007;Gray et al, 2006;MacDonald et al, 2008). The observation that the MFCV maximal value was reached in correspondence of T-Vent, could suggest that a progressive recruitment of larger MUs occurred from the onset of the exercise up to T-Vent, which could represent the point of full MU recruitment.…”

“…In the last decades, several studies (Merletti et al, 1990(Merletti et al, , 2001Merletti and Roy, 1996;Mannion and Dolan, 1996;Molinari et al, 2006;Rainoldi et al, 2008a, b;Nussbaum, 2001;Kaljumäe et al, 1994 among others) have demonstrated the usefulness of spectral EMG parameters to give evidence of the so called ''myoelectric fatigue" in sustained isometric and dynamic exercises, consisting of a decrease in mean or median frequency of the power EMG spectrum. More recently, the role of spectral parameters in this respect has been replaced by MFCV that seems to be a more robust and reliable (Farina et al, 2004;MacDonald et al, 2008) parameter to describe such phenomena. The decrease in MFCV that we observed could be the neuromuscular expression of muscle fatigue.…”

“…Among the indicators extracted from sEMG, the muscle fiber conduction velocity (MFCV) has been shown to be a suitable indicator of neuromuscular control behaving as a ''size principle" parameter (Andreassen and Arendt-Nielsen, 1987), thereby providing evidence of the motor units (MUs) recruitment strategies during dynamic exercises of various intensities (Farina et al, 2007;Gray et al, 2006). The reliability of MFCV during incremental and fatiguing cycling exercise has been also recently demonstrated (MacDonald et al, 2008). In particular, recently a positive relationship between MFCV, power output corresponding to the lactate threshold, and V 0 O 2max (Farina et al, 2007).…”

Análise da técnica de pedalada durante o ciclismo até a exaustão

“…Os resultados desses estudos sugerem aumento no VO 2 devido ao processo de instalação da fadiga, o que corrobora com os achados no presente estudo. O aumento no VO 2 para uma mesma carga de trabalho vem sendo associado ao recrutamento de unidades motoras de maior calibre na tentativa da manutenção da potência desejada (LUCIA et al, 2000;MACDONALD et al, 2008). Além disso, o fato do teste de carga constante ter sido realizado no domínio severo (100% da potência máxima) explicaria o aumento observado no VO 2 , de maneira monoexponencial, até os seus valores máximos (GAESSER;POOLE, 1996).…”