It’s a good idea to lay off training for a while if you get injured; however, it’s not a good idea to lay off your nutrition plan at the same time. When you injure a muscle, ‘in a sense the body panics and sends out a general breakdown alert. Proteolytic changes [muscle breakdown] are often seen in muscles far from the site of the injury,’ according to Nutrition Reviews (61:34-38, 2003). That protective mechanism enables the body to release amino acids for use in the tissues and for other functions, but, the article says, ‘as much as 26 percent of muscle protein can be lost within three days of the injury.’
One suggested solution is to inhibit muscle breakdown by using medications. That’s not the whole picture, though. According to the authors, ‘nutrition regimes should be developed to provide the amino acids that would have normally been provided from the breakdown of muscle protein following injury.’ That means getting a diet high in protein, with protein supplements as needed.
So take a rest from your training till your injury is healed, but continue to eat a balanced, high-protein diet so your body has plenty of amino acids available and doesn’t have to rob your muscles.