A Longitudinal Assessment Of Bone Mineral Density And Content In Competitive Cyclists

Abstract

Weight supported physical activity, such as cycling, is thought to provide insufficient stimuli to promote osteogenesis even though it incorporates significant muscular loading of bones. Furthermore, auxiliary factors such as dietary restrictions and low body mass in conjunction with confounders such as age, sex, competition level and the type of racing cloud the mechanisms of skeletal adaptations to cycling. PURPOSE: The purpose of this study was to investigate, in a diverse group of competitive cyclists, how age (18-49 years), sex, USA Cycling Category (elite-4) and racing type (road and multiple bike), influenced bone mass across a season. METHODS: In February, 2014, 42 participants (22 males, 20 females) completed a health history questionnaire, four day dietary log and a Dual-energy X-ray absorptiometry (DXA) scan. In September, 180 +/- 11 days later, participants repeated the measures. RESULTS: Pre-season subgroup analysis (age, sex, competition level and racing type) revealed significant differences in body composition, diet and cycling characteristics. Bone mineral density (BMD) T-Scores were within healthy limits and not different between groups (P≥0.053). Pre-season Body Mass was a significant correlate of T-Scores for older cyclists (R=0.584) and males (R=0.485), while BMI was a correlate for males (R=0.464). A significant time*group interaction with age suggests older cyclists may increase BMD across the season compared to younger cyclists. Post-season, Body Mass (R=0.623) and Total kcal (R=0.607) were significantly correlated with older cyclist’s T-Score, Total kcal was correlated with T-Score in males (R=0.601), and vitamin D was a correlate in females (R=-0.535). CONCLUSION: The results of this study suggest that participation in competitive cycling might not have deleterious effects on BMD and BMC as previously demonstrated. T-Score and regional BMD measurements did not significantly decrease across the season for any group; however, certain variables such as body composition, insufficient nutrition and time spent cycling are deserving of further investigation. More importantly, we must work to understand when, where and why cycling may shift from a safe osteogenic activity, as demonstrated by this study, to a possibly dangerous osteoporotic sport, as demonstrated by many others.