Impact of sensorimotor training on the rate of force development and neural activation.

The ability to generate high muscular strength within short time periods is of functional importance not only as a basic quality in many sports disciplines but also for active stabilization of joints. The rate of force development (RFD) is generally used to describe this ability. The purpose of the present study was to examine the functional adaptations of a specific sensorimotor training on the explosive strength qualities of the leg extensor muscles during maximum isometric actions. Force and surface EMG were recorded in 17 subjects before and after a 4-week sensorimotor training period. Maximum static leg press strength did not change [608.2 (47.0) N to 627.8 (48.4) N before/after training], whereas maximum RFD (RFD(max)) increased significantly from 4.95 (0.48) N/ms to 6.58 (0.76) N/ms (P<0.05). The gain in RFD(max) was accompanied by an increased EMG of the M. vastus medialis. Enhancement of neuromuscular activation was only prominent in the early phases of muscular action. Neither force nor EMG parameters revealed significant improvements for time phases beyond 100 ms following the onset of isometric action. Enhanced extrafacilitatory drive from the afferent system is discussed as a potential mechanism for the improved neural activation. From a more functional point of view, this type of adaptation may be helpful in various sport performances. Moreover, with regard to injury related situations, enhanced neuromuscular activation is of distinct relevance in order to stiffen joint complexes actively within short time periods.