-day muscle fatigue, without the need to log long or hard mileage," says coach Susan Paul (trackshack.com). After two to three miles easy, do six to eight reps of squats, lunges and calf raises (if you're in the gym, add leg extensions and leg curls). Do two
and building core strength for good posture will help prevent injuries," says Pierce.Here's howAfter doing the envelope run (above), do two sets of the following: 30 seconds each of press-ups, squats and crunches; 60 seconds of planks and calf raises; 90
