Motor strategies and bilateral transfer in sensorimotor learning of patients with subacute stroke and healthy subjects. A randomized controlled trial

Background: Bilateral transfer, i.e. the capacity to transfer from one to the other hand a learned motor skill, may help the recovery of upper limb functions after stroke. Aim: To investigate the motor strategies at the basis of sensorimotor learning involved in bilateral transfer. Design: Randomized controlled trial. Setting: Neurorehabilitation Hospital. Population: Eighty right-handed participants (65 ± 13 years old): 40 patients with subacute stroke, 40 control healthy subjects. Methods: Subjects performed the 9 hole-peg-test twice in an order defined by random allocation: first with low and then with high skilled hand (LS-HS) or the reverse (HS-LS). Time spent to complete the test and filling sequence were recorded, together with maximum pinch force (assessed using a dynamometer), upper limb functioning (Motricity Index), spasticity (modified Ashworth Scale), limb dominance (Edinburgh Handeness Inventory). Results: As expected, in patients, the performance was found related to the residual pinch force (P<0.001), upper limb motricity (P=0.006) and side of hemiparesis (P=0.016). The performances of all subjects improved more in HS-LS than in LS-HS subgroups (P=0.043). The strategy adopted in the first trial influenced the velocity in the second one (P=0.030). Conclusion: Bilateral transfer was observed from high to low skilled hand. Learning was not due to a mere sequence repetition, but on a strategy chosen on the basis of the previous performance. Clinical rehabilitation impact: The affected hand of patients with subacute stroke may benefit from sensorimotor learning occurred with the un-affected hand.