Effect of femoral quadriceps muscle length on fatigue and oxygen capitation induced by neuromuscular electrical stimulation.
electrical stimulation; angle-torque ratio; myotendinous unit; near-infrared spectroscopy.
The neuromuscular electrical stimulation (NMES) is frequently applied in the rehabilitation and improvement of the function of the musculoskeletal system. One of the limitations for the wide use of NMES is the rapid onset of fatigue. The length of the myotendinous unit (MUT) is a determinant of neuromuscular fatigability, but the mechanisms of NMES in the femoral quadriceps in different lengths of the MUT, considering the hip and knee angles, have not been demonstrated. Near Infrared Spectroscopy (NIRS) is a non-invasive tool that has recently been used in the evaluation of fatigue through of analyses muscle oxidative metabolism. Objective: To investigate the effects of manipulation of the femoral quadriceps musculotendine length on neuromuscular fatigue through NIRS. Methods: This is an experimental, randomized, double-blind crossover trial composed of up to 36 apparently healthy participants (18-45 years old) of both sexes. The NMES protocol will occur at 20% of the maximum voluntary contraction in the positions: bench press with knee at 60° flexion (Sup 60), seated with knee at 60° (Seat60), bench press with knee at 20° (Sup 20) and seated with knee at 20° (Seat20). The protocol will consist of 20 contractions in four sessions separated by 72h. NIRS data will be collected before, during and after the sessions. The same current amplitude will be maintained throughout the protocol. Expected results: Greater oxygen uptake is expected in positions where the knee is at 60° regardless of the hip position.