Skeletal muscle mass and bone mineral density in masters cyclists and moderately active young men

Abstract

Exercise mode and intensity/duration are important factors for influencing muscle morphology and function. Recent studies reported that cycle training resulted in significant quadriceps muscle hypertrophy and increased muscular function regardless of age. We hypothesized that master cyclists who undergo regular moderate to high intensity exercise should maintain lower-body skeletal muscle mass compared with young adults.PURPOSE: To examine the effects of long-term cycling training on age-related muscle loss of the lower body, our cross-sectional study compared absolute and relative skeletal muscle mass between master cyclists and moderately active young adults.METHODS: 12 male masters cyclists (aged 53-71 years) and 12 moderately active young men (aged 20-30 years, exercising less than twice a week) volunteered for this cross-sectional study. The master cyclists were actively training 4-5 times per week (∼200 miles per week), for on average, the last 17 years (range 7-38 years). Subjects who performed regular high-intensity resistance training were excluded from this study. Total skeletal muscle (SM) mass was estimated from an ultrasound derived prediction equation using muscle thickness (MTH). Appendicular lean mass (aLT) and areal bone mineral density (aBMD) was also estimated using dual-energy X-ray absorptiometry.RESULTS: There were no significant differences in SM mass index (9.1 (SD 0.9) vs. 8.7 [SD 1.0] kg/m2) and aLT index (8.8 [SD 0.9] vs. 8.3 [SD 1.0] kg/m2) between master cyclists and young men. Anterior and posterior MTH ratio was similar between groups (0.89 [SD 0.12] and 0.88 [SD 0.11], respectively). Isolated MTH of the gastrocnemius medialis was higher (p=0.04) in young men than in master cyclists, although vastus lateralis MTH was similar between groups. Maximum and zigzag 10-meter walking times were similar between groups. Lumber spine (L1-L4) aBMD was also similar between groups, but femoral neck aBMD was lower in the cyclists than in the young men.CONCLUSION: Our results suggest that appendicular as well as site-specific thigh muscle loss with aging was not observed in master cyclists. This maintenance of muscle mass in master cyclists may preserve walking performance to similar levels as moderately active young men. However, long-term cycling does not preserve femoral neck aBMD.