Effects of contralateral activity on muscular strength: a pilot investigation
Zhou, S & Hui, H 2003, 'Effects of contralateral activity on muscular strength. A pilot investigation', Second annual conference of the Society of Chinese Scholars on Exercise Physiology and Fitness: Health and Fitness for All, Macua, China, 24-27 November, Macau Polytechnic Institute and The Society of Chinese Scholars on Exercise Physiology and Fitness, Macau, China. ISBN:9993733563
The purpose of the present study was to investigate the acute effect of contralateral limb activity on the force generation capacity of one limb. Twenty university students (10 men and 10 women), aged 19 to 33years, with average (+/-SD) body mass 71.0+/-12.8kg and height 174.7±9.9cm, provided their informed consent and voluntarily participated in the study. Each subject was given a familiarisation trial of the experimental procedure within one week prior to the formal testing session. During the experiment, the knee extension torque in isometric contractions was recorded from both legs, while the subject sitting in the testing chair with the hip and knee joint angle at 90 degrees and a force transducer strapped to each leg just above the ankle joint. Electrodes for surface EMG were placed over the vastus lateralis muscle. The left leg was used as the criterion limb and produced a series of maximum voluntary knee extensions (MVC), while (1) the right leg was relaxed, (2) the right leg produced a maximum knee extension simultaneously, and immediately after the right leg (3) received a brief electric shock, or produced a contraction at (4) 30%, (5) 70% or (6) 100%MVC levels, respectively. The results indicated that simultaneous bilateral contraction, as compared to unilateral contraction, did not significantly affect the force generation capacity of the left leg. However, the MVC torque produced by the left leg was significantly increased when the right leg produced a contraction at 100%MVC immediately before the left leg contraction (condition 6) as compared to conditions 1, 3 and 4 (All p<0.05 as detected by repeated measures ANOVA with Bonferroni adjustment). The left leg torque was also higher when the right leg produced 70%MVC (condition 5) as compared with 30%MVC (condition 4). There was no gender difference in the above mentioned results, although the absolute torque produced by males was significantly higher that that by females. It summary, the results of present study indicated that the prior contralateral contraction at 70%MVC and above had significant acute effect on subsequent force generation of the ipsilateral limb. The practical significance of this phenomenon in strength training and/or exercise performance requires further investigation.