Differences in Tibia Bone Strength Between Collegiate Rowers and Sedentary Males

Abstract

Increased mechanical loading exerts site-specific positive effects on bone density, geometry and strength across a wide variety of sports. In particular, research shows beneficial effects of weight-bearing sports (e.g. soccer, running, and gymnastics) on tibia bone strength, but little research has examined the effects of rowing at similar sites. While not-weight bearing, increased lower-body peak forces generated during rowing, may result in more robust lower extremity bone structure over time compared to non-athletes. PURPOSE: To investigate the effects of rowing on tibia bone geometry, volumetric density, and strength differences among male collegiate rowers compared to sedentary controls. METHODS: Study participants included ten collegiate male rowers with a mean 2.2±0.6 years rowing experience and seven sedentary males from an existing database, all aged 18-23 years. Air-displacement plethysmography was used to obtain measures of body composition (fat mass, kg; fat-free mass, kg) in the rowers. The distal (4%) and midshaft (66%) non-dominant tibia sites were scanned using peripheral quantitative computed tomography (pQCT) to acquire bone outcomes. Total cross-sectional area (ToA), total volumetric density, and bone compressive strength were assessed at the distal (4%) site. Proximal tibia (66%) site outcomes included ToA, cortical thickness, cortical volumetric density, and bending strength. RESULTS: There were no significant differences between rowers and controls in height (cm; 182.2±6.0 vs.180.3±9.8), or weight (kg; 80.2±6.6 vs. 85.9±18.8), respectively. Rower’s mean fat-free mass (kg) was 68.4±7.4 and fat mass.(kg) was 10.8±3.5. Total weekly physical activity (including rowing practice) for rowers was 5.9±0.8 days. Finally, there were no significant differences in bone structure or strength between groups at the tibia 4% or 66% sites. CONCLUSIONS: Despite high peak forces generated during rowing, tibia volumetric bone density, geometry, and strength were similar between male collegiate rowers and sedentary controls. This lack of differences may be attributed to the relatively short training history among the rowers and anthropometric similarities with sedentary controls. Future research should include larger numbers of rowers and controls to further explore the possible effects of rowing on tibia bone geometry, volumetric density, and strength.