Weight training enables you to strengthen your muscles and build muscular endurance through exercises that challenge your major muscle groups to work harder, thus stimulating them over time to become stronger and to develop more endurance. This conditioning process improves the neuromuscular connectivity of your mind and body and builds muscle tissue. Weight training uses many forms of resistance including weight machines, free weights, elastic tubing and bands, or body weight. Resistance training conditions your muscles and the connective tissue that includes your tendons and ligaments, and strengthens your bones. As you become stronger, your energy level and your ability to do physical work increases.

Your Major Muscle Groups

A well-balanced resistance training program includes exercises for all of your major muscle groups. The major muscle groups of your body include the following:

• Chest

• Back

• Shoulders

• Front of upper arm

• Rear of upper arm

• Buttocks

• Front thighs

• Rear thighs

• Calves

• Abdominals

Your workout needs to include at least one exercise for each of these major muscle groups to create balanced muscle development. Muscles exist in opposing groups and work together synergistically. The biceps (the muscle in the front of your upper arm) and triceps (the muscle in the rear of your upper arm) is an example of a muscle pair. When the biceps contracts and shortens, the elbow bends and the triceps lengthens. When the triceps contracts and shortens, the arm straightens and the biceps lengthens. Well-balanced muscles support joints and improve stability. Lack of balance in muscular development contributes to poor posture, unstable joints, and an increased risk of aches, pains, and injury.

Muscle Function: Movers and Stabilizers

Your skeletal muscles provide two basic functions: movement and stability. The muscles and skeleton give the body structure, form, and the ability to move. For example, when you walk and take a step, you're using many muscles, including several muscles of the lower body: the muscles of your calves, thighs, hips, and buttocks. At the same time that these larger muscles are enabling you to move, other muscles are supporting your spinal column and hips, making sure that you keep your balance and move efficiently. Most of the “mover” muscles of the body are closer to the surface, while the “stabilizer” muscles lie deeper within, closer to the spinal column. Some muscles function as both movers and stabilizers depending on the particular action of the body.

The function of specific muscles is relevant when it's time to decide whether the goal of your training is to improve strength or endurance. Most mover muscles need a combination of strength and endurance. In contrast, stabilizer muscles primarily need high levels of endurance conditioning to function at their best.