For ultra you need experience

Is ultra unhealthy? A study sums up:
journals.plos.org - Health and Exercise-related Medical Issues among 1,212 Ultramarathon Runners: Baseline Findings from the Ultrarunners Longitudinal Tracking (ULTRA) Study


"Running reminds you that, even in your weakest moments, you are strong."
Dorothy Beal

See also:
runultra.co.uk - Map of ultra events 
statistik.d-u-v.org - Results database