Jumping jacks are such a traditional exercise that you may not realize the muscular benefit they provide. The path of movement performed in a jumping jack, with both legs and arms opening out and up, is done in the frontal plane. In this plane of movement, your shoulder and hip muscles are performing abduction and adduction. Abduction muscles move your limbs away from midline, and adduction muscles move your limbs toward midline. Your thighs, buttocks and calves power the jump.
Shoulder Abduction and Rotation
The arm movement involved in a jumping jack is complex, because your arm raises up and rotates. This movement involves your arm as well as your clavicle and scapula. Multiple bones and multiple muscles work together. The largest muscle at work is your trapezius, which runs from the base of your skull, down your neck, across the top of your shoulders and attaches to your scapula, clavical and spine. The next muscle involved is your deltoid, which is located on the side of your shoulder. The medial and anterior portions are more involved in the action. Finally, a small muscle called supraspinatus is used for rotation and abduction.
Hip abduction is the action of moving your legs away from midline and out to the sides. Two gluteal muscles perform this action: gluteus medius and gluteus minimus. The gluteus medius originates at the arching portion of your hip bone, called the ilium, and it inserts on the middle portion of your femur, which is your thigh bone. Its partner muscle, gluteus minimus, lies just beneath it. Together, these two muscles, when contracted, raise your legs out to the sides. Therefore, when you spread your legs in a jumping jack; gluteus medius and gluteus minimus are at work.
Hip adduction is the movement of bringing your legs together, toward midline. The muscles that perform this action work in opposition to the muscles that abduct your hips. Therefore, the jumping jack exercise promotes body balance. The team of muscles engaged in adduction is usually called the inner thigh. Their official names are adductor magnus, adductor longus, adductor brevis and pectineus. They originate in different places of your lower pelvic bone and they insert all along your femur.
Hip, Knee and Ankle Extension
Extension is the word used to describe opening the angle of a joint. A jumping jack contracts muscles to open the joints of your hip, knee and ankle. This forceful action strongly engages your gluteus maximus, which is your largest buttocks muscle. It also strongly engages your thigh muscles, called vastus lateralis, vastus intermedius, vastus medialis and rectus femoris. The last leg muscles used in a jumping jack are located at the back and sides of your calf. The large bulging muscle at the top is called gastrocnemius. Just underneath is the soleus muscle. Smaller active jumping jack muscles are peroneus longus, peroneus brevis, flexor hallucis longus, tibialis posterior and flexor digitorum longus.
- Fitness Theory and Practice; Aerobics and Fitness Association of America
- YMCA Personal Training Manual; YMCA of the USA
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