This section of the Grand Theft Auto V game guide describes triathlon. You'll learn what triathlon includes, how to prepare, and then participate in a triathlon in GTA 5.
Triathlon is a swimming, bike and running race in one. It's a great way to increase stamina of all three characters and injure your fingers from constant clicking.
The rule of all three races is simple. Left analog controls where you move while pressing A/X constantly speeds you up.
If your character has low stamina, he will get tired sooner so you will have to slow down or don't bother with that and start losing health points.
After two normal triathlons, you unlock the third one, The Coyote Cross Country Triathlon, which takes half an hour. Before choosing it make sure that your character has good stamina. Pause it regularly also to give a break for your fingers.