More than half of all ankle and knee injuries in female high school athletes can be prevented with a good warm-up routine, say researchers.

Ninety coaches participated in the study, leading their teams of female athletes through the same 20-minute session of strengthening, balancing and agility exercises before every game and practice. In the control group, the athletes stuck to their regular warm-up routine.

Over the course of the season, the coaches kept track of the number and type of injuries the girls sustained, noting how many games the girls missed due to injury.

Of the approximately 750 girls who consistently did the 20-minute warm-up prescribed by the researchers, there were 50 knee, ankle and leg injuries, compared to 96 in the control group of 750 that did no extra stretching and strengthening.

"We really feel like it should be a routine part of sports training for teenage girls. It's worth the investment," Cynthia LaBella of Northwestern University’s Feinberg School of Medicine told ReutersHealth of the extra warming up.

She says she and her colleagues found that when the coaches in the control group were instructed to do warm-ups as usual, they generally didn't do them at all or had athletes do warm-ups themselves.

The findings, which were published last week in the Archives of Pediatrics & Adolescent Medicine, calculated that three or four coaches would need to be trained in the warm-up exercises to prevent each non-contact injury.