Strength gains have been attributed to neural adaptations such as alterations in recruitment, rate coding, synchronization of motor units, reflex potentiation, co-contraction of antagonists, and synergistic muscle activity. Although most training studies show increases in EMG, a few have shown increase in strength with no apparent changes in neural drive. This may highlight the importance of motor control and the reorganization of supraspinal inputs. High intensity concentric and eccentric contractions with arousal and imagery techniques merit further study in promoting optimal neural adaptations. Specificity of training mode, type of contraction, and angle and velocity have been documented. Most velocity specificity studies have emphasized movement rather than contraction speed, which may be the predominant factor. The high rate of force development achieved with ballistic contractions should serve as a template for power training. The extent of muscle hypertrophy is dependent upon protein degradation and synthesis, which may be enhanced through high intensity, high volume eccentric and concentric contractions.
(C) 1995 National Strength and Conditioning Association