Longitudinal Assessment of Bone Mineral Density and Body Composition in Competitive Cyclists

Baker, BS and Reiser II, RF. A longitudinal assessment of bone mineral density and body composition in competitive cyclists. J Strength Cond Res 31(11): 2969-2976, 2017-Competitive cycling has been associated with low bone mineral density (BMD); however, BMD is a multifaceted issue. The purpose of this study was to investigate how age (18-49 years), sex, USA Cycling Category (elite-4), and racing type (road and multiple bikes), influenced body composition across a season in competitive cyclists. February marked the preseason, where 42 participants (22 males, 20 females) completed a health history and cycling questionnaire, 4-day dietary log and a dual-energy X-ray absorptiometry scan, and repeated the measures 180 ± 11 days later. Preseason BMD and Z-Scores were within healthy ranges and similar between sexes, age groups, competition levels and racing-type groups (p ≥ 0.053). Age was significantly correlated with whole group BMD (r = 0.309; p = 0.047). Postseason analysis revealed very encouraging findings as no significant changes in BMD or Z-Score were observed in any group (p ≥ 0.067). A significant main effect for time was found in all groups as lean mass (LM) decreased and fat mass increased across the season (p ≤ 0.001). Additional analysis showed a significant time × group interaction as cat. 1 riders decreased body mass and body mass index, whereas cat. 4 riders responded in the opposite direction (p ≤ 0.037). Postseason correlations highlighted significant positive relationships between BMD and age, LM, and Kcal ingested (r ≥ 0.309; p ≤ 0.047). The only significant negative correlate of BMD was percent body fat (r = -0.359; p = 0.020). Armed with this information, cyclists and coaches should aim to prioritize balance between body mass and caloric intake while meeting the demands of training to minimize risk of cycling related low bone mass.