Abstract des Autors

The surface electromyogram (EMG) from active muscle and oxygen uptake (VO2) were studied simultaneously to examine changes of motor unit (MU) activity during exercise tests with different ramp increments. Six male subjects performed four exhausting cycle exercises with different ramp slopes of 10, 20, 30 and 40 W/min on different days. The EMG signals taken from the vastus lateralis muscle were stored on a digital data recorder and converted to obtain the integrated EMG (iEMG). The VO2 was measured, with 20-s intervals, by the maxing chamber method. The results demonstrated that the VO2max and VO2 at which a nonlinear increase in iEMG was observed were not varied by the change of ramp slopes but by the exercise intensity corresponding to VO2max and the iEMGbp was varied by the change of ramp slopes but by the exercise intensity corresponding to VO2max and the iEMGbp was varied by the change of ramp slopes. In addition, the significant differences in the VO2 exercise intensity slopes for the upper half of the tests would suggest that the recruitment patterns of MU and /or muscle metabolic state might be considerably altered depending upon the ramp slope increments.