Specific Neck Training Induces Sustained Corticomotor Hyperexcitability as Assessed by Motor Evoked Potentials

Abstract

Experimental investigation of short-term and long-term corticomotor effects of specific neck training, coordination training, and no training. To determine the effects of different training programs on the motor neurons controlling the neck muscles as well as the effects of training on muscle strength and muscle fatigue, and the correlations between corticomotor control and motor learning. Training is usually recommended for unspecific neck pain and consists of neck and upper body coordination, strengthening, and endurance exercises. However, it is unclear which type of training is the most effective. No studies have previously investigated the neural effect of neck training and the possible differential effect of specific versus coordination training on corticomotor control. Transcranial magnetic stimulation and electromyography were used to elicit and monitor motor evoked potentials (MEPs) from the trapezius and thumb muscles before and 30 minutes, 1 hour, and 7 days after training. Parameters measured were MEP amplitude, MEP latency, strength, learning effects, and muscle fatigue. Only specific neck training yielded a 67% increase in MEP amplitudes for up to 7 days after training compared with baseline (P < 0.001). No significant changes were seen after coordination training, no training, and in the within-subject control muscle. The mean muscle strength increased immediately after specific neck training from 56.6 to 61 kg (P < 0.001). No subjective or objective measures of fatigue were observed. Specific neck training induced a sustained hyperexcitability of motor neurons controlling the neck muscles compared with coordination training and controls. These findings may prove valuable in the process of developing more effective clinical training programs for unspecific neck pain.