Fluid retention, muscle damage, and altered body composition at the Ultraman triathlon.
Level 4 - case-series / case-control
Prospective single-arm observational cohort without a comparison group.
PubMed 26560107 · doi:10.1007/s00421-015-3291-9
What was done
Eighteen triathletes (14 male, 4 female; age 41 ± 7.5 years, weight 73.5 ± 9.8 kg) were monitored across a 3-day ultraendurance triathlon (Stage 1: 10 km swim, 144.8 km bike; Stage 2: 275.4 km bike; Stage 3: 84.4 km run). Participants were assessed before and after each stage. Outcomes included body mass and composition (bioelectrical impedance), hydration status (urine specific gravity), blood glucose (fingerstick), and venous blood markers of muscle damage (creatine kinase), inflammation (C-reactive protein), and hormones (aldosterone, cortisol, testosterone).
What was found
The abstract reports effect sizes and correlation coefficients rather than raw numerical values: - Body composition: Significant reductions occurred in body mass (trivial effect size), fat mass (moderate effect size), and percent body fat (small effect size). Percent total body water increased (moderate effect size), while absolute total body water and fat-free mass were unchanged. - Hydration and metabolism: Urine specific gravity increased (large effect size), and blood glucose increased in a stepwise manner prior to each stage. - Muscle damage and endocrine markers: Creatine kinase, C-reactive protein, aldosterone, and cortisol demonstrated extremely large post-race increases. Testosterone (small effect size) and the testosterone-to-cortisol ratio (moderate effect size) decreased. - Correlational findings: Negative associations were reported between post-race aldosterone and total body water (r = -0.504) and between changes in cortisol and fat-free mass (r = -0.536).
Why it matters
The study outlines the multi-day physiological impact of extreme multi-stage endurance racing, documenting concurrent hormonal stress, severe muscle breakdown, and alterations in fluid distribution and body composition.
Limits
The sample size was small (n = 18) with few women (n = 4), precluding sex-stratified analysis. There was no control group. Body composition was estimated via bioelectrical impedance, which is vulnerable to measurement error during acute fluid and electrolyte fluctuations. The abstract reports qualitative effect size classifications rather than absolute pre- and post-race mean values. Fluid and caloric intake during the event were not described in the abstract.
Cited by
- supports The Ultraman triathlon consists of a 6.2-mile swim, a 261-mile bike ride (90 miles on day one and 171 miles on day two), and a 52.4-mile double marathon run over three days.