EFFECTS OF GYMNASTICS TRAINING ON VOLUMETRIC AND AREAL SPINE BMD

Abstract

PURPOSE: Bone gains and losses have been reported in gymnasts following seasonal training and detraining periods however, reports of seasonal changes in the spine of gymnasts has been limited to areal calculations from anterior-posterior (AP) projections using dual energy x-ray absorptiometry. Our aim was to assess the effects of gymnastics training on areal and volumetric measures of spinal bone mineral density (BMD) in gymnasts and controls. METHODS: Subjects consisted of 9 intercollegiate gymnasts and 15 normally active controls. Height (by stadiometer) and BMD and weight (by DXA, QDR-4500/A, Hologic Inc., Waltham, MA) were assessed at the beginning and end of an academic year (9 months). During this time gymnasts engaged in their competitive training season whereas controls were normally active. Lumbar spine measurements included areal BMD (G/CM2) in the AP projection and volumetric BMD (G/CM3) from coupled AP and lateral projections. Compared to controls, gymnasts were slightly older (19.33 ± 0.37 vs. 18.33 ± 0.13, p < .01) and had a later age at menarche (14.44 ± 0.63 vs. 11.93 ± 0.33, p < 0.01) but BMI was similar between groups (gym = 23.9 ± 0.58 con = 23.0 ± 0.65) and did not change over the academic year. Furthermore, groups did not differ for calcium intake and the average values were close to or within the RDA (gym = 943.9 ± 99.5 con = 1145.9 ± 141.9). By ANCOVA, adjusting for initial BMD values, 9-month changes in areal and volumetric BMD were not significantly different between groups (Table 1). However, compared to controls, changes in areal and volumetric BMD were more than 5- and 10-fold greater in gymnasts (Table 1). In conclusion, while we did not observe significant differences between groups for 9-month change in areal or volumetric spine BMD, we attribute the non-significant findings to low power, due to the small sample size, and short follow up period.Table 1: Lumbar Spine Areal and Volumetric BMD in Gymnasts (n = 9) and Controls (n = 15) (mean ± SE)