How do decathlon people train?

Answer 1

Bruce Jenner revolutionized the sport before the 1976 Olympics by training 8 hours a day, essentially a full time job to practice the variety of disciplines. During this period, athletes were not allowed to make money from their athletic accomplishments. His (then) wife Chrystie Crownover supported him with her job as an airline stewardess. After he won the Olympic Gold medal (in world record form) he quit the sport to make money from his celebrity. He even left his vaulting poles in the Olympic stadium. Now that athletes are professional, his successors have followed the same training model.

There are some events whose attributes fight one another, so athletes focus on what will get the most points. For example, bulking up to throw well, works against the 1500 and really sprinting and jumping.