Influence of physical activity and cessation of training on calcaneal quantitative ultrasound measurements in peripubertal girls: a 1-year prospective study.

The aim of this 1-year follow-up study was to investigate the influence of physical activity and cessation of competitive training on the changes in the sonographic parameters among healthy peripubertal girls. We used calcaneal quantitative ultrasound measurements. A total of 174 peripubertal Caucasian girls aged 11-17 years (61 gymnasts, 58 runners, and 55 nonathletic controls) were studied. Weight, height, stage of puberty, years of training, and the amount of leisure-time physical activity were recorded. Twenty-one sports participants (9 gymnasts, 12 runners) discontinued their training (retired) within 6 months from the baseline. The broadband ultrasound attenuation (BUA) and the sound of speed (SOS) through the calcaneus were recorded. The mean baseline BUA and SOS values of the nondominant calcaneus of the gymnasts were 11.9% (72.6 dB/MHz vs 64.9 dB/MHz, P < 0.05) and 2.0% (1600.4 m/s vs 1569.2 m/s, P < 0.001) higher than that of the controls, respectively. The baseline BUA and SOS values of the gymnasts and runners were similar. The mean 1-year increase in BUA was significant in the controls and sports participants who continued their training, whereas the change of BUA among the retired sports participants was not. The mean 1-year increases of SOS of the runners and controls were 6.6 m/s (95% CI 1.5 m/s to 11.7 m/s, P < 0.05) and 3.5 m/s (95% CI 0.5 m/s to 6.4 m/s, P < 0.05), respectively. In contrast, the SOS value among the retired runners declined and the 1-year change of SOS was -12.8 m/s (95% CI -22.1 m/s to -3.6 m/s, P < 0.05). The 1-year change of SOS among gymnasts was not significant. We conclude that the beneficial effect of exercise on the sonographic parameters of the calcaneus is evident but, at least partly, temporary. The SOS value decreases significantly soon after cessation of training and it may reflect the deterioration of the quantity and quality of bone without sufficient mechanical loading.