D-23 Free Communication/Poster - Aging and Exercise in Health and Disease

Abstract

Running and cycling have been reported to have negative effects on bone health; however, few studies have directly compared the bone status of these two groups. PURPOSE: This study compared areal BMD (aBMD) and volumetric BMD (vBMD) in competitive male runners and cyclists. The influence of energy availability on BMD was also assessed. METHODS: Male runners (n=18) (yr racing 7.3 ± 1.3) and road cyclists (n=19) (yr racing 4.8 ± 0.8) 20-50 yr participated in this study. Total body, lumbar spine, and dual hip aBMDs were obtained by DXA. Tibia and femur bone variables were assessed by pQCT. Energy availability ([energy intake - exercise energy expenditure]/fat free mass) was estimated from 7 day dietary and activity logs. Questionnaires were filled out to assess calcium intake, training and bone loading history. RESULTS: Energy availability was not significantly different between runners and cyclists (181.6 ± 23.4 vs.194.8 ± 22.0 kcal/kg, respectively); and it was not correlated with bone variables. After adjusting for age, runners had significantly (p<0.05) higher aBMD, T-scores, and Z-scores than cyclists for femoral neck and left total hip. Runners had significantly (p<0.05) higher total and trabecular bone mineral content (BMC) (tibia 4%) and higher total vBMD (tibia 66%) than cyclists. However, cyclists had a significantly higher strength strain index (SSI), total area, periosteal and endosteal circumferences (tibia 66%) than runners. CONCLUSION: There were site-specific differences in bone characteristics between runners and cyclists. Runners had better bone status for the hip, whereas the cyclists had greater bone strength for the tibia 66% site.Table 1: Bone Variables (Adjusted Mean ± SE)