Symptoms of overtraining include feelings of malaise, staleness, depression, poor performance and more risk of injury. According to livestong.com, muscles don't recover from a strength training workout for at least 7 to 10 days. That means plenty of rest is required to help the muscle recover while also boosting muscle mass. Without proper rest, you are setting yourself up for overtraining and other issues. There are occurrences of severe muscle damage where athletes did not let the muscles fully heal. To ensure that you are implementing enough periods of rest, maintain a training log where you record your workout sessions. With it there in black and white, you can set aside your days off from working out.