According to a recent study cited in this New York Times article, the answer is "yes":
The study found that sleep onset latency — the time it takes to fall asleep once in bed — ranged from as little as roughly 10 minutes for some children to more than 40 minutes for others. But physical activity during the day and sleep onset at night were closely linked: every hour of sedentary activity during the day resulted in an additional three minutes in the time it took to fall asleep at night. And the children who fell asleep faster ultimately slept longer, getting an extra hour of sleep for every 10-minute reduction in the time it took them to drift off.
Studies on adults have reached generally similar results, showing that an increase in physical activity improves sleep onset and increases sleep duration, particularly in people who have trouble sleeping.So stop relying on your Ambien prescriptions and go work out, people.