Perceived and measured fatigue of lumbar muscles in competitive, master and fin swimmers

Increase of training loads in young athletes performing aquatic sports is related with increased injury rate. The lumbar muscles and shoulder joint are the principal localization of injuries. Each aquatic sport, differently stress the spine. Objective of the study is to investigate the influence of the aquatic sports practice on measured (surface EMG median frequency decay per minute) and perceived fatigue of lumbar muscle (Borg CR-10 scale of perceived exercption). The experimental design was to test three groups of swimmers were compared with th-test for paired samples. The tests were performed on the side of an indoor pool. The groups were composed as following : 1)competitive swimmers (n = 31) 2) master swimmers (n = 15) and 3) fin swimmers (n=18). Main outcome measure were median frequency decay of the surface EMG and Borg CR-10 ratings during a modified Biering-Sorensen test. Results: female master swimmers showed less EMG (objective) fatigue of lumbar muscles than female competitive swimmers (t = 4.6 p = 0.010). female fin swimmers show less EMG (objective) fatigue than female competitive swimmers (t=2.9, p = 0.027). No statistical difference was found in EMG between female master and female fin swimmers. Perceived fatigue was less pronounced in male fin swimmers than in male master swimmers ( t = 2.6 p = 0.048). Male competitive swimmers didin't show any significant difference from master and fin swimmers. Consent from the subjects was obtained after the explanation of the aims, procedure and modalities of the test. Conclusions: in general, older swimmers experienced less fatigue of the lumbar muscles. Specific adaptations induced by the sport causes a better tolerance to lumbar muscles fatigue in fin swimmers.