Rest days are so important because they are an opportunity to recuperate from the stresses of training. Unless you are injured, doing nothing isn’t ideal. Try a light active recovery day with exercises that will help increase the blood flow to the muscles. If you are listening, your body will tell you when you need a rest day. Pay attention to the signs–if you have sudden low energy, depressed moods, an elevated resting heart rate, interrupted sleep, dehydration, illness, pain or soreness–you may be at risk for injury.