LOWER TRUNK MUSCLE ACTIVITY DURING THE TENNIS SERVE

Abstract

971 The purpose of this study was to examine the activation patterns of the left and right rectus abdominis (RA), external oblique (EO), internal oblique(IO), and lumbar erector spinae (ES) muscles during three different types of tennis serve - flat, topspin, and slice - using surface electromyographic(EMG) techniques. Five male collegiate tennis players served as the subjects. Each subject performed 10 trials for each serve type and the average values of two selected trials for each serve type were used for analysis. Average EMG values were computed for different phases of a tennis serve. Means were compared across serve type using an ANOVA for repeated measures (p ≤.05). The results showed no major difference in muscle activation pattern across serve type and that bilateral differences in muscle activation were more pronounced in the RA and EO than in the IO and ES. In general, the left muscle activity was more pronounced than the right over a greater duration during the serve. In the acceleration phase (from end of windup to ball impact), bilateral difference was found only in RAs. This suggests that the obliques are responsible for the trunk flexion and RAs help to maintain the side-bent posture during this phase. The abdominal muscles seemed to be more active in the topspin than the other two types of serve during the upward swing of the racket. A high degree of abdominal/low back and bilateral co-contraction was observed during certain phases of the serve. The co-contractions and the hyperlordotic posture may place considerable stress on the lumbar intervertebral joints and cause lumbar spine injury.