Forced reps are a great way to take a set past muscle failure. Growth hormones increase 200% compared to a workout without using forced reps. Take a set to failure, then with the assistance of a spotter, have the sponsor provide just enough help to keep the set going. If you train alone, spot yourself in single arm workouts such as on a preacher bench. Do 2 or 3 reps of failure at the end of each set to ensure continued muscle growth.