Neuromuscular Recruitment Characteristics Of Quadriceps Femoris Muscles During Wingate Anaerobic

Por: A. C. Moraes, , , E. S. Cyryno, Ewerton Rodrigo Gassi e R. O. Okano.

Athens 2004: Pre-olympic Congress

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The Wingate anaerobic test (WAnT) consists of 30 s of maximal intensity cycle ergometer test and has been used
extensively to evaluate anaerobic cycling performance. The decline in power output during WAnT has been associated
with several metabolic changes in the exercising muscle [2]. However, Bangsbo et al. [1] have show that other factors
such as neural control mechanisms may be important determinants of the fatigue that develops in high intensity
exercise. To our knowledge, the only study to have examined neuromuscular characteristics during the 30 s WAnT was
that of Hunter et al. [3], however, this study is limited for one reason. They recorded EMG signal during WAnT, but
only in the Rectus Femoris (RF) muscle. Therefore, the aim of the present study is to investigate the neuromuscular
recruitment characteristics of Vastus Lateralis (VL), Vastus Medialis (VM), and RF during WAnT.

Eight males cyclists (age 26.9 ± 6.4 years; body mass 74.8 ± 8.7 kg; height 179.6 ± 9.4) performed a 30 s WAnT on a
cycle ergometer (Monarkâ) at a resistance corresponding to 90 of the body mass [5]. A surface electromyogram
was recorded from electrodes placed over the belly of the VL, VM, and RF. Relative power output (RPO) and Root
Mean Square amplitude (EMG-RMS) were recorded throughout the cycling.
Power output decreased significantly over a 30 s of WAnT. The response of EMG-RMS was not significantly different
among muscles groups during the entire period of the WAnT, however some differences in the behavior of EMG-RMS
were observed for the contracting muscles. After the 15th second, the magnitude of the decrease of EMG-RMS in RF
was larger than that recorded for VL and VM.

Discussion / Conclusions
The different EMG-RMS signal patterns between the VL, VM, and RF may be explained by morphological,
architecture, and biomechanical characteristics of each muscle. The RF is a bi-articular muscle and is related to
controlling the distribution of net moments about the joints [4], while VL and VM are mono-articular muscles. The RF
is a muscle with a predominance of fast, type II fibres than VL and VM, and are more susceptible to fatigue. The RF is
a muscle that had a smaller cross-sectional area [6]and reflects in less tension production than VL and VM. We
concluded that the differences in morphology, architecture, and biomechanics of muscles induced in specific motor
strategy of RF and could be reflected in a different motor unit activity, which may have produced different signal
characteristics of EMG-RMS during WAnT.

[1]. Bangsbo et al. (1992). J Physiol, 451, 205-227.
[2]. Green (1997). J Sports Sci, 15, 247-256.
[3]. Hunter et al. (2003). Br J Sports Med, 37, 296-299.
[4]. Jacobs & Van Ingen Schenau (1992). J Physiol, 457, 611-626.
[5]. Okano et al. (2001). Revista Brasileira de Ciência e Movimento, 9, 39-44.
[6]. Wickiewicz et al. (1983). Clin Orthop, 179, 275-283.

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