The aim of the current study was to investigate the EMG activity of pectoralis major and latissimus dorsi muscles during the pullover exercise. Eight healthy male volunteers took part in the study. The EMG activity of the pectoralis major and that of the latissimus dorsi of the right side were acquired simultaneously during the pullover exercise with a free-weight barbell during both the concentric and eccentric phases of the movement. After a warm-up, all the subjects were asked to perform the pullover exercise against an external load of 30% of their body weight, during 1 set × 10 repetitions. The criterion adopted to normalize the EMG data was the maximal voluntary isometric activation. The present findings demonstrated that the barbell pullover exercise emphasized the muscle action of the pectoralis major more than that of the latissimus dorsi, and the higher activation depended on the external force lever arm produced.
Paulo H. Marchetti and Marco C. Uchida
Paulo H. Marchetti, Maria I.V. Orselli, and Marcos Duarte
The aim of this study was to investigate the effects of unilateral and bilateral fatigue on both postural and power bipedal tasks. Ten healthy subjects performed two tasks: bipedal quiet standing and a maximal bipedal counter-movement jumping before and after unilateral (with either the dominant or nondominant lower limb) and bilateral (with both lower limbs) fatigue. We employed two force plates (one under each lower limb) to measure the ground reaction forces and center of pressure produced by subjects during the tasks. To quantify the postural sway during quiet standing, we calculated the resultant center of pressure (COP) speed and COP area of sway, as well as the mean weight distribution between lower limbs. To quantify the performance during the countermovement jumping, we calculated the jump height and the peak force of each lower limb. We observed that both unilateral and bilateral fatigue affected the performance of maximal voluntary jumping and standing tasks and that the effects of unilateral and bilateral fatigue were stronger in the dominant limb than in the nondominant limb during bipedal tasks. We conclude that unilateral neuromuscular fatigue affects both postural and power tasks negatively.