Scientists just tested the fittest 81-year-old in the world - highest VO2 max ever recorded for an 80 y.o. (52.8 ml/kg/min - equivalent to average 20-year-olds) - world record for 50 km run in his age group (04:47:39) - world record for the marathon in his age group (03:39:10) That's an insane level of fitness for someone in their 80s And the crazy part - he only started exercising at the age of 66 Video breakdown: Full study: