The effect of gymnastic training on muscle strength and co-activation during isometric elbow and glenohumeral flexion/extension.

BACKGROUND: The purpose of the study was to demonstrate the differences between non-athletes and gymnasts at the pre- and post-pubertal age in the development of peak torque and ensuing flexion/extension ratios at the elbow and the glenohumeral joints, as well as to assess the relevance of the above activities for the co-activation of selected muscles.

METHODS: The study involved 20 gymnasts and 20 non-athletes aged 8-9 years, in addition to 12 gymnasts and 16 non-athletes aged 18-25 years. Measurements of the isometric peak torque (PKTQ) were taken for flexion and extension at the elbow and the glenohumeral joints. The method of surface electromyography (EMG) was applied in order to determine the neurophysiological characteristics of the strength and capabilities of these joints.

RESULTS: In the group of older gymnasts the PKTQ ratio of the glenohumeral flexors to extensors was the lowest (0.72) and was significantly different from the other groups. This result was consisted with the 30% higher PKTQ values (P<0.01) of the glenohumeral extensors and a 41% reduction in their EMG in flexion in comparison to non-athletes.

CONCLUSIONS: Apart from demonstrating the effects of long-term gymnastic training, the results give information about the imbalance between the agonists and the antagonists of the arm, which can predispose to more frequent injuries. A disproportionately greater development of strength capabilities of extensor muscles in relation to arm flexors among experienced gymnasts can provide valuable information for physiotherapists and coaches on individuation of athletes' special preparation - essential in teaching many complex gymnastic exercises.