Male Runners With Lower Energy Availability Have Impaired Skeletal Integrity Compared to Nonathletes

Abstract

Context Female athletes, particularly runners, with insufficient caloric intake for their energy expenditure (low energy availability or relative energy deficiency) are at risk for impaired skeletal integrity. Data are lacking in male runners. Objective To determine whether male runners at risk for energy deficit have impaired bone mineral density (BMD), microarchitecture, and estimated strength Design Cross-sectional Setting Clinical research center Participants 39 men (20 runners, 19 controls), ages 16-30y Main Outcome Measures Areal BMD (DXA); tibia and radius volumetric BMD and microarchitecture (high resolution peripheral quantitative CT); failure load (microfinite element analysis); serum testosterone, estradiol, leptin; energy availability (EA) Results Mean age (24.5 ± 3.8y), lean mass, testosterone, and estradiol levels were similar; BMI, percent fat mass, leptin, and lumbar spine BMD Z-score (-1.4 ± 0.8 vs. -0.8 ± 0.8) lower (p < 0.05); and calcium intake and running mileage higher (p ≤ 0.01) in runners vs. controls. Runners with EA < median had lower lumbar spine (-1.5 ± 0.7, p = 0.028), while runners with EA ≥ median had higher hip (0.3 ± 0.7 vs. -0.4 ± 0.5, p = 0.002), BMD Z-scores vs. controls. After adjusting for calcium intake and running mileage, runners with EA < median had lower mean tibial total and trabecular volumetric BMD, trabecular bone volume fraction, cortical porosity, and apparent modulus vs. controls (p < 0.05). Appendicular lean mass and serum estradiol (R ≥ 0.45, p ≤ 0.046), but not testosterone, were positively associated with tibial failure load among runners. Conclusions Despite weight-bearing activity, skeletal integrity is impaired in male runners with lower caloric intake relative to exercise energy expenditure, which may increase bone stress injury risk. Lower estradiol and lean mass are associated with lower tibial strength in runners.