Save the heavy workouts for earlier in the day, and try soothing stretches and balance work near bedtime. Being very active and maintaining your cardiovascular fitness and strength will help you sleep more soundly at night, so long as your big workout doesn't happen too close to bedtime. Unwinding with stretching or calming yoga poses is a fine idea. Taking a leisurely evening walk is fine, too. But within 2 or 3 hours of bedtime, you should not engage in any activity that raises your heart rate above its resting rate. Why? Vigorous exercise raises your levels of the stress hormone cortisol, an enemy of sleep.