A strength imbalance is when you are stronger in one movement than you are in its opposing movement. If you are stronger with pressing exercises, such as pushups, than you are in pulling exercises, you have a strength imbalance. Strength imbalances can cause you to reach a strength plateau in which you cease to improve, and can lead to overuse injuries if left uncorrected.
Muscles Trained by Pushups and Pullups
Pushups are pushing exercises. The primary muscles trained are the pectoralis major of your chest. Your deltoids and triceps also contribute to the movement. Your core muscles work to stabilize your body throughout the movement. Pullups, on the other hand, are a pulling exercise. They primarily train the latissimus dorsi, the large muscles of your back. The biceps and other muscles that work to flex your elbow are also involved, as well as your core and other stabilizing muscles.
Your muscles pull on your bones in order to create movement. Your pectoral muscles pull your upper arm bones forward, while your latissimus dorsi muscles pull them back. When these opposing sets of muscles are in balance, your shoulder joints receive equal amounts of tension. When one set of muscles is stronger than the other, the tension is unequal. At rest, the stronger muscles are shorter than they should be, and the weaker muscles are overstretched. This can lead to postural problems or uneven wear on your neck and shoulders.
Consequences of Strength Imbalance
You are more likely to be stronger in pushups or the bench press than in pullups, so the more common strength imbalances result in shortened pectoral muscles. When these muscles are shortened at rest, they pull your shoulders forward, and rotate the bones of your upper arms inward. This tilts your head forward. In compensation, you begin holding your neck forward and bent upward. The muscles that retract your shoulder blades, the rhomboids, are lengthened at rest, which can lead to shoulder tendinitis.
Correcting and Preventing Strength Imbalances
Performing an equal volume of pullups and pushups is the simplest way to prevent a strength imbalance. You move 70 percent of your bodyweight in a pushup, as opposed to your full weight with a pullup, so a ratio of three pushups for every one pullup is often sufficient. It is also important to move through a pullup's full range of motion. Continuing to pull until your chest touches the bar will fully contract your latissimus dorsi and rhomboids, and fully stretch the pectoral muscles.