NEW YORK (Reuters Health) - Elite swimmers appear to experience higher rates of lower back disk degeneration than recreational swimmers, study findings suggest.

A screening study of 56 male and female competitive swimmers identified lower back disk degeneration in 68 percent, report Dr. Koji Kaneoka, University of Tsukuba, and colleagues at the Japan Institute of Sports Sciences.

By comparison, among 38 male and female recreational swim club members, lower back disk degeneration was evident in 29 percent -- a rate similar to that of the general population, the researchers note in the American Journal of Sports Medicine.

Kaneoka and colleagues suggest that "excessive competitive swimming activities" may account for higher rates of disk degeneration among the elite swimmers, who had been swimming, on average, more than 49,000 meters weekly for over 9 years. The recreational swimmers, on the other hand, reported swimming about 8,400 meters weekly for 5.4 years, on average.

Using magnetic resonance imaging, the investigators spotted disk degeneration in the lumbar spine in the both groups of swimmers, particularly between the fourth lumbar (L4) and the first sacral (S1) vertebrae - the area where the lower back joins the pelvis.

The competitive swimmers had significantly higher rates of degeneration, 27 and 43 percent in the L4-L5 and L5-S1 disks, respectively, compared with rates of 13 and 21 percent in the recreational swimmers.

There was no relationship between disk degeneration and the swimmers' most frequently used strokes.

Kaneoka's team undertook the study after three of 39 members of the Japanese national swim team were impeded by lumbar disk herniation in an international competition. Despite the findings from the current study, however, the researchers say further investigation is needed to confirm any association between swimming frequency and duration and disk degeneration in the lower back.