Kelvin Kiptum of Kenya holds the male world record for the marathon. His time? 2:00:35. He can run 42.2km (26.2 miles) in seconds over 2 hours. That’s running 2:51 per km (or 4:36 per mile) for 2 hours. Not only was he the first person to get under 2:01 for the marathon, but he also ran the second half faster than the first half (called a negative split). While training for this feat, Kelvin would have put his body through progressive stress, time and time again. Breaking dow
