During ultra endurance events, athletes experience extreme physical and mental demands, sometimes at the limits of the adaptive response to human physiology. This is particularly true for the renal function, and some evidence for acute renal failure has already been shown, sometimes leading to dialysis. However, the precise mechanisms involved in acute renal failure in such ultra endurance races are not clearly elucidated.

The aim of our study is to estimate glomerular filtration rate from serum and urinary creatinine and cystitin C at the beginning and at the end of a 110 km ultra endurance race. Our hypothesis is that during the ultra endurance race, renal function may be injured, with a risk for the athlete.

Inclusion Criteria:

• Age: At least 20 years old
• Athlete that is officially registered to the 110 km race (INFERNAL Trail des Vosges)
• Athlete informed by a member (MD) of the Medical Staff of the race.
• Athlete that gives and signes the informed consent to the research protocol

Exclusion Criteria:

• Athlete with a known disease that needs the following medications:
• Medications influencing the renin-angiotensin-aldosteron system (angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, aldosteron receptor blockers)
• Diuretic drugs
• Anticoagulant drugs
• Non-steroidal anti-inflammatory drugs
• Athlete with a known thyroid disease (because of the influence on the serum cystatin level)
• Athlete with a know renal disease
• Athlete with a know inflammatory disease