Estimating energy availability and examining its association with bone mineral density in male cyclists.

摘要

Research indicates that male cyclists are at risk for low bone mineral density (BMD), which has largely been attributed to the lack of bone loading afforded by the sport of cycling. There may, however, be other reasons for the low BMD seen in male cyclists including low energy availability resulting from attempts to reduce body weight in order to improve power-to-weight ratio. The purpose of this pilot study was to assess energy availability (EA) and bone health, as well as examine the association between these variables among elite male cyclists (n= 22) as compared to age-matched, nonathletic controls (n=22). EA was determined using 3-day weighed food and activity records designed to capture 3 distinct training days (heavy, moderate and easy). Exercise energy expenditure was calculated using the compendiums for physical activity. Bone health was determined by measuring areal bone mineral density (aBMD) of the lumbar spine and left hip using dual energy x-ray absorptiometry (DXA) and from self-reported stress fracture incidence. Descriptive statistics were calculated and Pearson Chi-square (X 2) analyses were used to examine associations between low EA and aBMD. The results indicated that EA was significantly lower in the cyclists compared to controls (17.7 +/- 8.9 kcal-kg-1 FFM-d -1 vs 33.86 +/- 9.8 kcal-kg-1 FFM-d -1, P<0.05). 91% of the cyclists (n= 20) and 41% (n= 9) of the controls had "low" EA (≤ 30 kcal-kg -1 FFM-d-1) (P= 0.001). None of the cyclists and 4 of the controls met the "optimal" EA value of ≥ 45 kcal-kg -1 FFM-d-1. Spinal aBMD was lower in cyclists vs. controls (0.950 + 0.12 kg/m2 and 1.045 + 0.11 kg/m 2, respectively, P= 0.010). Significantly more cyclists (73%, n= 16) than controls (32%, n= 7) had low spinal aBMD (P< 0.05). Hip aBMD was also lower in the cyclists (0.944 +/- 0.14) compared to controls (0.989 +/- 0.13), and more cyclists (32%, n= 7) than controls (9%, n= 2) had low hip aBMD, although these differences were not statistically significant. There were no statistical associations between low EA and aBMD at either the spine or hip for either the cyclists or the controls. Despite the lack of a statistical association, the high prevalence of both EA and low BMD in these elite level cyclists warrants further longitudinal investigation and a greater focus on intervention strategies to prevent potential health consequences while maintaining or optimizing cycling performance.