Rest Days have mechanical, metabolic and mental benefits...
Depending on training intensity and overall volume, taking rest day(s) are essential to both injury prevention and to athletic performance. Fitness gains are the product of work + recovery. If the training volume exceeds the body's ability to recover between efforts, athletes can suffer from metabolic debt. If soft tissue doesn't have the resources it needs to repair; tendon injuries, muscle strains and even stress fractures can result.
Rest days can look a few different ways. There are active rest days and passive rest days. An active rest day should be used to accomplish one of two things, cross training or metabolic flushing. Cross training offers the opportunity to vary the mechanical stress of running, but still create the metabolic load to improve fitness. It is also helpful to work other muscle groups that can get neglected if running is your only activity. Metabolic flushing is like doing the dishes. It’s hard for tissue to repair itself without adequate blood flow. Metabolic flushing is getting the heart rate up, but not keeping it there. These should be short efforts that don’t cause additional metabolic debt, but instead kick start the body's systems to aid in repair.
True rest days should not involve any metabolic loading or high heart rate activity. Remember the heart is also a muscle and it needs time to recover as well. On true rest days doing low heart rate, and low intensity activities are still fine. In fact, sitting or lying on the couch all day can lead to muscle tightening and restricted blood flow, which will delay recovery. Using a foam roller, percussion massage gun or pneumatic compression boots are all great ways to improve blood flow without changing the heart rate. Practices like yoga, meditation and stretching should be gentle and restorative. Use these to help the mind recover as well as the body. Blood Flow Restriction is another tool that can be beneficial. This first deprives tissue from blood flow to create oxygen debt, then when released floods the area with fresh blood supply. This can be repeated on several body parts to improve recovery time, again without additional stress on the heart.
Getting massage, acupuncture, chiropractics or physical therapy can also be a good use of a rest day, but might even be more effective if done after a run on a training day and use the day after your treatment to recover from the treatment.
Rest days should not be used to pig out! Pigging out is better to aid recovery following a big effort on a high volume day. On rest days you want to give all of your systems a break. On rest days you want to drink additional fluids and eat small frequent healthy meals. This will help make sure you have good availability of nutrients to properly repair tissue and recover metabolically.
-Douglas Bertram, CEO and Founder