Tomographical description of tennis-loaded radius: reciprocal relation between bone size and volumetric BMD

Effects of long-term tennis loading on volumetric bone mineral density (vBM D) and geometric properties of playing-arm radius were examined. Paired for earms of 16 tennis players (10 women) and 12 healthy controls (7 women), ag ed 18-24 yr, were scanned at mid and distal site by using peripheral quanti tative computerized tomography. Tomographic data at midradius showed that t ennis playing led to a slight decrease in cortical vBMD (-0.8% vs, nonplayi ng arm, P < 0.05) and increase both in periosteal and endocoritcal bone are a (+15.2% for periosteal bone, P < 0.001; and +18.8% for endocortical bone, P < 0.001). These data suggest that, together with an increase in cortical thickness (+6.4%, P < 0.01), cortical drift toward periosteal direction re sulted in improvement of mechanical characteristics of the playing-arm midr adius. Enlargement of periosteal bone area was also observed at distal radi us (+6.8%, P < 0.01), and the relative side-to-side difference in periostea l bone area was inversely related to that in trabecular vBMD (r = -0.53, P < 0.05). We conclude that an improvement of mechanical properties of young adult bone in response to long-term exercise is related to geometric adapta tion but less to changes in vBMD.