Neuromuscular electrical stimulation (NMES) has been used as a neuromuscular rehabilitation method for many years. Recently, quantitative NMES intensity on muscular strength training has not been reported with significant findings. We investigate if different electrical stimulation intensity showed different effects in increasing muscle strength of quadriceps femoris (QF), thigh circumference and athletic performance of healthy men. The ES training mode in this study was quantified and using median frequency (2500Hz) stimulation that modulated to 50 bursts per second. The intensity of ES was set at 60% and 30% of maximal voluntary isometric contraction (MVC) of QF at knee flexion 60 degree. 23 healthy male were randomly assigned into 60% MVC (N=7), 30% MVC (N=7) and control group (N=9). 12 training sessions each included 15 times of ES to QF of non-dominant (ND) side lasted for 4 weeks. The ES duty cycle was 10 seconds of ES which induced isometric contraction at knee flexion 60 degree and then 50 seconds for rest. The isometric, concentric, and eccentric strength of both thighs were evaluated by Kin-Corn 500H before and after ES training. The athletic performance and fat composition were tested as well. The results showed 1. The isometric strength increased percentage of ND-QF of 60% MVC group were significant greater than 30% MVC group and control group at knee flexion 90 and 60 degree. 2. The ND eccentric strength at different speed all increased significantly in 60% MVC and 30% MVC groups with comparison to the control group. 3. No significant improvement in the athletic performance was found in either group. The results suggested that the ES training appeared to be effective in developing isokinetic and isometric strength of QF, but no influence to the athletic performance and fat composition.
