Laterality Of Maximal Muscle Strength Of Knee And Hip Joints In Weightlifter

Abstract

The bimanual lifting requires the muscles of both lower limbs to work symmetrically. The athletes who require symmetrical movements make their endeavor to get a well-balanced neuromuscular function between both legs and arms. The symmetry of maximal strength of each joint should influence the symmetry parameters during the lifting. In developing the performance level, how do the symmetrical levels of maximal muscle strength change? PURPOSE The purpose of this study was to evaluate symmetrical levels of maximal muscle strength of knee and hip joints in developed weightlifters. METHODS Eight healthy college weightlifters including two female lifters participated in this study. They were higher, level college weightlifters and one female lifter had won the Japanese college championship. Maximal voluntary strength in knee extension and flexion were measured isokinetically at the three constant velocities of 60, 180 and 300 deg·sec−1. Maximal voluntary strength in hip extension and flexion were measured isokinetically at the three constant velocities of 30, 60 and 120 deg·sec−1. Each subject performed three trials at each velocity in each leg. The peak values at each trial were adopted as maximal muscle strength of each velocity in each leg. These tests were repeated one year after the first ones. Symmetrical indices were indicated as the following calculation: abs ((left − right)/right)*100 (%). RESULTS Our subjects developed their performances. The average increasing rate of competition record was 11.0% during the one year between the first and second measurements. The obtained maximal muscle strength data showed that knee extension strength at each velocity increased 4.5, 13.8 and 8.2%, respectively. In the knee flexion strength, improvement rates were less than 3.0%. Hip extension strength at each velocity remarkably increased. The improvement rates of hip extension during the one year were 18.5, 25.2 and 30.0%; on the other hand, those of hip flexion were less than 6.0%. The subjects increased their hip extension strength and also improved their symmetrical levels. CONCLUSIONS In the weightlifting, the lifter is needed to exert the explosive power by lower limbs and to control symmetrically both right and left limbs. Previous data showed that hip extensor torque was most important and had much higher values. From our results, it was shown that developed college weightlifters improved their strength level and symmetrical level during the year. It is interesting that hip extension strength and symmetrical index remarkably increased, because hip extension is the key of the explosive power output during the weightlifting.