Your muscles grow in response to stress. Heavy weights are one of the ways to introduce this stress and to encourage muscle growth. You can't go for just one heavy-lifting session and hope to come out looking bigger and feeling stronger. Muscle growth is a complex, gradual process that requires regular training.
Muscle Growth 101
Lifting weights traumatizes the muscle cells, triggering your body to repair them. Satellite cells outside the muscle are triggered by the trauma and rush to help. They fuse together and to existing muscle fibers to increase the size of the existing muscle. The muscle fibers also go into a state of repair by forming new protein strands, making them thicker and stronger.
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Weights are Traumatizing
Heavy weights are best to induce the necessary damage to the muscle cells to stimulate the process of growth. Lift for three to six sets of eight to 12 repetitions of an exercise. You should use 80 to 85 percent of your one-repetition maximum. Rest 30 to 60 seconds between these sets. Leave at least 48 hours between heavy workouts for specific muscle groups.
Weights Aren't Enough
Diet and sleep are also important factors in muscle growth. You need an additional 250 to 500 calories per day to fuel muscle growth. A protein intake higher than average also gives your muscles adequate amino acids to assist with repair. Aim for between 0.55 and 0.7 grams per pound of body weight daily. You'll need seven to nine hours of sleep, which is when your body releases human growth hormone for muscle growth.