Abstract
Skeletal growth is positively affected by weight-bearing exercise activities. Although cross-sectional studies indicate a positive effect of rhythmic gymnastics (RG) training on bone volumetric density, there is limited number of RG training studies in the pediatric population. Our objective was to test the hypothesis that prolonged RG training affects positively bone metabolism of pre-adolescent girls. A two-group, repeated measures design was employed. 40 healthy, previously sedentary, pre-adolescent girls were randomly assigned to either: a) a control group (C, N=16, 8.5 ± 1.8 yrs) that participated only in school physical education classes and b) a RG training group (RGT, N=14, 8.1 ± 1.8 yrs). RGT trained 90 min per practice, three times/week for 8 months. Maturity status was determined using Tanner diagrams of five pubertal stages. Daily habitual physical activity was monitored by accelerometry and daily nutritional intake was measured with diet recalls in both groups. Volume and intensity of physical education activity in C and training in RGT was measured by accelerometry, heart rate monitoring and jump count. Physical performance (FIT test battery), bone density by DXA and anthropometrics (body weight and height, arm span, tibia length, body composition) were measured pre- and post-training. The two groups demonstrated similar anthropometric profile, performance and bone density at baseline. After training, RGT exhibited lower (P= 0.001) body weight and body fat, better (P= 0.01) performance in tests of the FIT battery and greater bone density and bone mineral content at the femur, lumbar spine and wrist. The control group demonstrated a modest increase in bone density and bone mineral content at femur and lumbar spine. There were no differences between groups in nutritional intake. Our results indicate that 8 months of intensive RG training provides a sufficient stimulus for gains in bone density and bone mineral content of pre-adolescent girls above those induced by physical education classes and daily physical activity.