Site-Specific Effects of Swimming on Bone Density in Female Collegiate Swimmers

While swimming provides numerous cardiovascular and overall health benefits, past research suggests it provides no constructive benefits to bone strength and density at dual energy x-ray absorptiometry (DXA) measured hip and lumbar spine sites when compared to sedentary individuals. However, little research has focused on skeletal sites stressed by muscle forces during swimming such as the humerus, hip, and radius. The purpose of this study was to investigate site-specific bone strength adaptations among female collegiate swimmers compared to sedentary controls. Bone geometry and strength were assessed by DXA and peripheral quantitative computed tomography (pQCT) in ten female collegiate swimmers and ten sedentary controls (<150 minutes/week of moderate-to-vigorous physical activity) ages 18-23 years. There were no significant differences between groups in the DXA-derived outcomes. Among pQCT-measured sites, the control group had a 14.8% greater bone cortical area and 6.1% greater cortical volumetric density compared to swimmers (both p<0.05) at the proximal tibia (66%) site. Hip structural analysis was also performed to observe the strength and loading power at the narrowest part of the proximal femur, but no significant differences were found between groups. With no significant bone density or strength differences between groups at the humerus, radius, or distal tibia sites, this research suggests that swimming may not have osteogenic benefits, even at site-specific locations commonly stressed during the sport. For overall health, these results suggest that swimming should be supplemented with weight-bearing and resistance exercises to preserve bone strength and prevent deterioration of bone as one ages.