Bilateral force control and coordination patterns across upper and lower limbs.

Bilateral force control and coordination in upper and lower limbs are important functions for executing activities of daily living. Although upper and lower limbs may reveal distinct bilateral motor control patterns because of different motor networks involvements, no one has examined the possibility that upper and lower limbs reveal distinct bilateral force control and coordination patterns. This study investigated bilateral force control and coordination patterns between upper and lower limbs in healthy young adults. Thirty-two healthy young adults (mean±SD of age = 23.2±2.2 years; 16 Females) performed bilateral hand-grip and ankle-dorsiflexion force control tasks at 10 % and 40 % of maximal voluntary contraction. Bilateral force control performances were evaluated by calculating mean force, force symmetry, force accuracy, and force variability. To estimate bilateral force coordination, we used cross-correlation with time lag. Further, we examined the relationship between bilateral force control and coordination patterns of upper and lower limbs by conducting Pearson's correlation analysis. Bilateral maximal and mean forces of lower limbs were significantly less than those for upper limbs. At higher targeted force level, force accuracy and variability in lower limbs were significantly lower than those for upper limbs. More negative correlation coefficient values appeared in lower limbs as compared with upper limbs. Finally, bilateral force control performances in upper limbs were related to those in lower limbs although no significant correlation was observed for interlimb coordination patterns. These findings suggest that bilateral motor control and coordination patterns were different between upper and lower limbs although the level of bilateral upper and lower motor control capabilities was presumably influenced by shared motor control processes for each individual. See also the graphical abstract(Fig. 1).