02163nas a2200193   4500000000100000008004100001653002400042653001200066100001600078700001600094700001200110700001500122700001100137245009200148300003700240490000800277050000600285520167800291       2006                            d10aPeer Reviewed Paper10aChecked1 aGandevia S.1 aHerbert Rob1 aMunn J.1 aCarroll T.1 aLee M.00aContralateral effects of unilateral strength training: evidence and possible mechanisms  a1514-1522. [Impact Factor 3.632]0 v101  aN3 a<p>
If exercises are performed to increase muscle strength on one side of the body, voluntary strength can increase on the contralateral side. This effect, termed the contralateral strength training effect, is usually measured in homologous muscles. Although known for over a century, most studies have not been designed well enough to show a definitive transfer of strength that could not be explained by factors such as familiarity with the testing. However, an updated meta-analysis of 16 properly controlled studies (range 15-48 training sessions) shows that the size of the contralateral strength training effect is approximately 8% of initial strength or about half the increase in strength of the trained side. This estimate is similar to results of a large, randomized controlled study of training for the elbow flexors (contralateral effect of 7% initial strength or one-quarter of the effect on the trained side). This is likely to reflect increased motoneuron output rather than muscular adaptations, although most methods are insufficiently sensitive to detect small muscle contributions. Two classes of central mechanism are identified. One involves a "spillover" to the control system for the contralateral limb, and the other involves adaptations in the control system for the trained limb that can be accessed by the untrained limb. Cortical, subcortical and spinal levels are all likely to be involved in the "transfer," and none can be excluded with current data. Although the size of the effect is small and may not be clinically significant, study of the phenomenon provides insight into neural mechanisms associated with exercise and training.
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