Doctor's Orders: Mix It Up
After every workout, I recommend getting in fast-digesting whey. That's because it gets to your muscles ASAP to kick-start muscle protein synthesis for optimizing muscle growth. There was a time when we recommended avoiding casein protein because it digested too slowly to be of any benefit around workouts—or so we thought. But then several studies showed casein in a different post-workout light, especially when combined with whey.
A Baylor University (Waco, Texas) study found that subjects who consumed a whey-casein mixture built more muscle mass than those consuming a whey shake without the added casein. Other studies showed slow-digesting casein still increased muscle protein synthesis after workouts, and it kept it turned on for longer. This likely explains why combining whey and casein after workouts increases muscle gains better than whey alone.
Make a post-workout shake containing 30 g of whey and 10 g of casein and consume within 30 minutes after training.
Remember that every rest day should be an active rest day. Rest days are for recovery; they're not an excuse to be lazy. Get out and hit 15-30 minutes of HIIT cardio today, or perform 30-60 minutes of your favorite activity: hiking, biking, walking, playing a sport, etc.