How can I be more productive in the gym?

Time your rest intervals. By carefully monitoring rest periods between sets, you can accomplish in 30 minutes what used to take an hour. What's more, your levels of muscle-building hormones will soar throughout your workout. This increases size and attacks your body's fat stores. Try resting 30 to 45 seconds between sets if your primary goal is endurance; 60 to 90 seconds for muscle growth; and 2 to 3 minutes between sets for serious strength gains.