From Isner’s epic 11-hour battle to Nadal and Djokovic’s grueling 5-hour semifinal, these tennis marathons pushed athletes to their limits and redefined endurance in sport.

In front of her home crowd, Sara Sorribes Tormo defeated a second seed in a row at the Mutua Madrid Open, upsetting No.23 seed Victoria Azarenka in the third round in 2 hours and 50 minutes -- the ...