(HealthDay News) — Participation in the endurance competition known as the Ultraman is associated with dramatic alterations in body composition, muscle health, hormones, and metabolism, according to a study published in the European Journal of Applied Physiology.

The 3-day Ultraman includes an initial 6.2-mile open swim and a 90-mile bike ride. On day 2, athletes complete a 172-mile bike ride, and on the final day they run a double marathon, or 52.4-miles. 

During the Ultraman competition last year in Florida, researchers assessed the health of 18 athletes, including 4 women. The athletes were weighed every morning before they competed, and they also provided urine and blood samples.

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The researchers found that, overall, the athletes lost body fat but they did not lose weight because they retained fluid. They also noted extremely large increases in creatine kinase, C-reactive protein, aldosterone, and cortisol, alongside reductions in testosterone and the testosterone:cortisol ratio. Blood glucose was found to rise in a stepwise manner prior to each stage.

“Given recovery, their insulin sensitivity likely returned to normal, but it was interesting to see how a presumably healthy activity can lead to symptoms associated with being very unhealthy,” study coauthor Daniel Baur, of the Florida State University Institute of Sports Sciences and Medicine in Tallahassee, said in a university news release.


  1. Baur DA, Bach CW, Hyder WJ, Ormsbee MJ. Fluid retention, muscle damage, and altered body composition at the Ultraman triathlon. Eur J Appl Physiol. 2015;doi:10.1007/s00421-015-3291-9.