Relationship between the modifications of bilateral deficit in upper and lower limbs by resistance training in humans

Maximal voluntary strength of simultaneous bilateral exertion is known to be small compared to the sum of the unilateral exertions. This phenomenon is called bilateral deficit and the purpose of this study was to investigate whether it operates in both upper and lower limbs. A group of 7 female and 32 male students were divided into 4 training groups and a control group. The unilateral arm or leg training group performed maximal isokinetic arm or leg extensions using each arm or leg unilaterally. The bilateral arm or leg training group trained using bilateral extensions of both arms or legs. The groups in training continued these two types of resistance exercise 3 days a week, for 6 weeks. The control subjects did not train. The improvement in power brought about by training was compared from the viewpoint of whether the limbs (arms or legs) were trained or not and whether the mode of test power exertion (bilateral or unilateral) was the same as performed during training or not. The power in the trained limbs using the same regime as that during training (3.0% after 3 weeks, 7.7% after 6 weeks) showed the largest improvement ratio. This agrees with the specificity theory in resistance training. The increase in power in untrained limbs using the same regime as during training (2.1% after 3 weeks, 3.5% after 6 weeks; P?P?