Throwing a baseball, whether you're playing outfield, second base or pitching, involves more muscle involvement that than found in the arm. Throwing a baseball encourages movement, contraction and power as well as coordination of movement from over a dozen muscles found from the upper torso down to your calves.
Shoulder
The motion of throwing a baseball focuses a great deal on the shoulder area, incorporating various muscle groups such as the rotator cuff, made up of four muscles -- the supraspinatus, infraspinatus, the teres minor and the subcapularis. These four muscles form a sheath or cap of muscle wrap around the upper head of the humerus and attach to the shoulder blade.
Upper Torso
Throwing a baseball also involves contraction and extension of several muscle groups in the upper torso including the rhomboids -- the major and minor -- which hold the shoulder blade in alignment with the spine and control shoulder movement, flexion, extension and range of motion. You also use your trapezius, a large muscle that extends from the base of your skull along the top of your shoulder attaching to the spinal side of the scapula to allow extension and retraction of the shoulder blade.
Arms
The anterior, middle and posterior deltoid muscles cover the top of the shoulder and insert at the upper head of the humerus, allowing you to flex, extend, abduct and rotate your arm, all-important functions when throwing a baseball. Gripping and releasing the ball involves multiple muscles of the fingers and hand as well as the wrist flexors and extensors of the forearm, which include but are not limited to the brachioradialis, and extensors such as the carpu radialis brevis and longus.
Chest
A major chest muscle called the pectoralis major covers the front of the chest and extends from the top of the humerus to the breastbone as well as the upper ribs. The pectoralis minor connects to the upper ribs and the distal portion of the scapula and enables you to move the scapula downward and forward, a motion also necessary to throw a baseball.
Abdominals
Throwing a baseball involves all the abdominal muscles, involving the rectus abdominus, a thick sheath of muscle that extends from your breastbone down to your pubis bone. You also use the muscles of your sides, called the external and internal obliques. These muscles give your body power and forward momentum, as well as allow your body to rotate on its axis, twist and bend as you throw.
Legs
You engage the hip flexor muscles, a group of six muscles found on the front side of your upper thigh or hip. These muscles enable you to propel the hips forward when stepping, walking or running, and for follow-through and step following a baseball throw.
Your buttocks, quadriceps, hamstrings of the upper legs and your calves, in the lower legs, are also used during a baseball throw, and offer propulsion and power to your efforts. The quadriceps muscles are located on the front of the thigh, the hamstrings on the backside. Calf muscles used to propel your torso weight forward and complete the throwing motion include the gastrocnemius, the larger muscle in the upper calf, and the soleus muscle, found directly beneath the gastrocnemius and attaches to the Achilles tendon.
References
- American Academy of Orthopaedic Surgeons: Rotator Cuff Tears
- Get Body Smart: Muscles That Act on the Shoulder
- The Complete Pitcher: Pitching Leg Strength; Jerry Kreber
- University of New Mexico: Super Abs Resource Manual; Len Kravitz, Ph.D.
- Richard Stockton College Athletic Training: Common Athletic Injuries -- Hip Flexor Strain; Jon Heck
- Gateway Community College: Major Superficial Muscles: Posterior Forearm
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