Resumen de Electromyographic Activity and Rate of Muscle Fatigue of the Quadriceps Femoris During Cycling Exercise in the Severe Domain

Thiago V. Camata, Leandro Ricardo Altimari, Henrique Bortolotti, Jose L. Dantas, Eduardo B. Fontes, Bruno PC Smirmaul, Alexandre H. Okano, Mara Patrícia Traina Chacon-Mikahil, Antônio Carlos de Moraes

• This study compared the activation pattern and the fatigue rate among the superficial muscles of the quadriceps femoris (QF) during severe cycling exercise. Peak oxygen consumption ([latin capital V with dot above]o2peak) and maximal accumulated oxygen Deficit (MAOD) were established by 10 well-trained male cyclists (27.5 ± 4.1 years, 71.0 ± 10.3 kg, 173.4 ± 6.6 cm, mean [latin capital V with dot above]o2peak 56.7 ± 4.4 ml·kg-1·min-1, mean MAOD 5.7 ± 1.1 L). Muscle activity (electromyographic [EMG] signals) was obtained during the supramaximal constant workload test (MAOD) and expressed by root mean square (RMS) and median frequency (MF slope). The RMS of the QF, vastus lateralis (VL) and vastus medialis (VM) muscles were significantly higher than at the beginning after 75% of exercise duration, whereas for the rectus femoris (RF), this was observed after 50% of exercise duration (p <= 0.05). The slope of the MF was significantly higher in the RF, followed by the VL and VM (-3.13 ± 0.52 vs. -2.61 ± 0.62 vs. -1.81 ±0.56, respectively; p < 0.05). We conclude that RF may play an important role in limiting performance during severe cycling exercise.