Abstract
PurposePhysical activity, particularly mechanical loading that results in high-peak force and is multi-directional in nature, increases bone mineral density (BMD). In athletes such as endurance runners, this association is more complex due to other factors such as low energy availability and menstrual dysfunction. Moreover, many studies of athletes have used small sample sizes and/or athletes of varying abilities, making it difficult to compare BMD phenotypes between studies.MethodThe primary aim of this study was to compare dual-energy X-ray absorptiometry (DXA) derived bone phenotypes of high-level endurance runners (58 women and 45 men) to non-athletes (60 women and 52 men). Our secondary aim was to examine the influence of menstrual irregularities and sporting activity completed during childhood on these bone phenotypes.ResultsFemale runners had higher leg (4%) but not total body or lumbar spine BMD than female non-athletes. Male runners had lower lumbar spine (9%) but similar total and leg BMD compared to male non-athletes, suggesting that high levels of site-specific mechanical loading was advantageous for BMD in females only and a potential presence of reduced energy availability in males. Menstrual status in females and the number of sports completed in childhood in males and females had no influence on bone phenotypes within the runners.ConclusionGiven the large variability in BMD in runners and non-athletes, other factors such as variation in genetic make-up alongside mechanical loading probably influence BMD across the adult lifespan.
Highlights
Bone mineral density (BMD) is considered to be the primary predictor of osteoporotic fracture (Cranney et al 2007) other factors such as geometry, architecture and collagen properties are important determinants of bone strength (Cheung et al 2016)
lumbar spine BMD (LSBMD) was 9% lower in male runners than non-athletes (P = 0.004) but there were no differences in TBMD (P = 0.176), LBMD (P = 0.963), T-score (P = 0.141) or Z-score (P = 0.092) between these two groups (Table 2)
LBMD was 4% higher in female runners than non-athletes (P = 0.015), but there were no differences in TBMD (P = 0.508), LSBMD (P = 0.110), T-score (P = 0.478) or Z-score (P = 0.847) between these two groups (Table 3)
Summary
Bone mineral density (BMD) is considered to be the primary predictor of osteoporotic fracture (Cranney et al 2007) other factors such as geometry, architecture and collagen properties are important determinants of bone strength (Cheung et al 2016). BMD may be important for success in the elite sporting environment due to the potential influence on training, performance and injury (Herbert et al 2019). The influence of mechanical loading on BMD in endurance athletes is more complex. Low BMD may increase the risk of stress fracture, which can have negative implications for health and performance (Hind et al 2006; Barrack et al 2008; Pollock et al 2010). Excessive training volumes and/or insufficient dietary intake by endurance runners can result in reduced energy availability, which can negatively impact metabolic processes and potentially reduce BMD (Loucks 2007). Lower BMD was more evident in those runners exhibiting menstrual irregularities (Pollock et al 2010) or where dietary restraint was occurring (Barrack et al 2008)
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