Association of Reduced Physical Activity and Quantitative Ultrasound Measurements: A 6-Year Follow-up Study of Adolescent Girls

Sonographic parameters of the heel were recorded in order to investigate the effects of changes in physical activities among 140 healthy growing peripubertal Caucasian girls. Calcaneal quantitative ultrasound measurements (Hologic Sahara) were recorded at baseline and 2- and 6-year follow-up. Broadband ultrasound attenuation, speed of sound (SOS), and T scores were documented. Altogether, 30 girls reduced their physical activity by >50% and 29 girls by 25–50%, whereas 81 girls continued at the present level or increased it. Age and physical activity together accounted for 16.7% of the variation in calcaneal T scores at baseline and for 16.4% at 2-year follow-up, whereas physical activity alone accounted for 11.3% of the variation at 6-year follow-up. The reduction in mean T scores was significant (from 2.0 to 0.8, P < 0.001) among those having discontinued their physical activity by the 6-year measurement. The changes between three groups were statistically significantly different from each other (P = 0.003). The mean SOS values decreased 16.78 meters per second (95% CI −26.9 to −6.7) among those having discontinued their physical activity between the 2- and 6-year follow-up measurements. The SOS value sensitively reacts to changes in physical activity, and consequently, it will help assess changes in bone quality. Because of such an immediate reaction, SOS is a good-quality measure for the physical condition of bone in young people and a suitable tool for detecting changes in calcaneal bone.