Effects of repetitive handgrip training on endurance, specificity, and cross-education

Background and Purpose. Exercise programs are more likely to be successful when they are based on research that predicts the outcomes of such training. This study determined the effect of submaximal rhythmic handgrip training on rhythmic handgrip endurance or work (RHW), isometric handgrip endurance time (IHE), and maximal voluntary isometric contraction for the handgrip force (MVIC) (in newtons). Subjects. Twenty-four male subjects (mean age=26.2 years) with right-hand dominance were randomly assigned to a regular training group (n=8), a low-level training group (n=8), or a control group (n=8). Methods. Rhythmic handgrip work, IHE, and MVIC were determined bilaterally before and after 6 weeks of a rhythmic right handgrip training program using 30% of MVIC. The low-level training group performed daily training with a near-zero load (<0.005% of MVIC). Results. There was a 1,232% increase in RHW and an 8% decrease in IHE after the training program using 30% of MVIC for the right hand. The left hand showed a 43% increase in RHW after training, whereas the low-level training group showed a 35% increase in RHW. No differences were found between the change in the left-hand RHW of the regular training group and the change in the right-hand RHW of the low-level training group, but both measurements were greater than the change in the control group (6.4%). Conclusion and Discussion. Submaximal handgrip endurance training at 30% of MVIC had a minimal effect on submaximal IHE and MVIC of the handgrip, but it had a large effect on RHW of the trained extremity. The regular training group and the low-level training group showed similar increases in cross-education, suggesting that cross-education during endurance training is not intensity-dependent.