Eugene, OR -- (Sports Network) - Sprinter Tyson Gay has a mild strain in the left hamstring muscle.

An MRI on Sunday showed the mild strain and Gay is expected to engage in "active rest" for the next two weeks, with physical activity increasing through that period, then resume training.

The sprinter fell during his 200-meter quarterfinal heat on Saturday at the U.S. Olympic track and field trials. He pulled up and tumbled within the first 50 meters of the race, and needed to be carted off the track. His agent, Mark Wetmore, said that Gay suffered a severe cramp.

Last Saturday at the trials, Gay set a new American record in the 100- meter sprint, clocking in at 9.77 seconds. One day later he ran a wind-aided time of 9.68 seconds in the final to win the event and clinch an Olympic berth.