After any hard training session, the body needs time to recover. Many people take rest days, avoiding any physical activity, in order to recuperate. While this is a great way to give yourself a break and prevent injury, it could cause more harm than good. If you're extremely sore remaining immobile could cause your muscles to tighten up as they recover. This means that when you get back in the gym things could be a little harder than they were the last time you hit the weights.
Active recovery, when done correctly, can reduce muscle soreness, and speed up the recovery process. It’s not intended to burn that many calories or to up your weights and resistance. Active recovery is about physically and psychologically recovering from the muscle and body stress of intense exercise, as well as lowering your heart rate and improving form. You can even perform active recovery as part of your cool-down from a HIIT session. Try using very light weights, yoga, foam rolling, or even a slow, 5-minute run. Try incorporating one active recovery day into your routine per week and see if it works for you! Remember, if you’re suffering from an injury, passive rest days are still the best option, you don't want to worsen the damage! So make sure to pay attention to your body and take the route that will best suit you.