Cross Education: Ipsilateral and Contralateral Effects of Unimanual Training

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Abstract
The bilateral influence of the unilateral practice of 4 standardized activities included in the MacQuarrie test of mechanical ability was studied on 50 normal young adult physical therapy trainees, 27 of whom were males. The test was first taken by the preferred and then by the nonpreferred hand. The group was then divided into 2 on the basis of equivalent hand dominance. 26 subjects practiced once weekly with the left hand and 24 practiced with the right. The expt. extended over a period of 8 wks. at the termination of which right- and left-sided performance was again measured. Statistical analysis of the data supports the following conclusions: (1) Manual dexterity improves significantly with direct practice. (2) In general, the mechanical ability of the dominant limb improves more with direct practice than that of the contralateral extremity. (3) The unpracticed contralateral extremity also improves significantly in mechanical ability. (4) Dextral improvement due to cross education does not approach that achieved by direct practice. (5) The sinistral or nonpreferred side may gain more as a result of practice by the contralateral limb than by ipsilateral direct practice but the differences are not significant. (6) The relative amount of motor learning taking place bilaterally appears to spread more nearly equally to the right and the left sides when training involves the less discrete pathways of the nonpreferred limb. The mechanism of cross education is discussed.
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