A study at the Defense Medical Rehabilitation Center in Surrey, the United Kingdom, followed more than 1,500 recruits during a grueling 14-week training program.
Half were told to do eight different types of exercise during every training session, focusing on strengthening their leg muscles and making them more flexible by stretching. The other half did standard military warm-up and cool-down exercises.
With traditional warm-ups, nearly 5 percent of the soldiers developed knee pain, but that number dropped to just over 1 percent among those who did the special exercises -- a 75 percent decrease, Russell Coppack and his colleagues wrote in the American Journal of Sports Medicine.
"A simple set of lower limb stretching and strengthening exercises resulted in a substantial and safe reduction in the incidence of AKP in a young military population undertaking a physical conditioning program," Coppack wrote.