Researchers recently looked at the first season of Major League Soccer in the United States to answer this question. There were 237 pro soccer players in the league. Each player spent about 241 hours in practice over the course of the season. That's eight times the number of hours they spent in competition. Even so, most injuries happened during games.

During practice, players had three injuries per 1,000 hours of playing time. Meanwhile, they had 35 injuries per 1,000 hours of game time. That means players were 12 times more likely to get hurt during games as compared to practice!

One-third of the injuries were so minor they didn't require any time off from the sport. Most of the remaining injuries kept players off the field no longer than a week. Still, these results show that competition may be more rigorous--and more risky--than practice.