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Save your shoulder: Mechanics behind a healthy tennis serve W ith tennis season in full swing, here are a few tips to keep you on your game. Protect your shoulder by training the kinetic chain. The kinetic chain encompasses transferring energy generated and stored in the legs through the core/abdominals/back and then powering the shoulder/elbow and finally to the wrist holding the racket. Below are four stages to the tennis serve where energy is transferred from one body part to the next, all working toward powering the racket. These stages were researched by van der Hoeven et al, 2006 and Elliott, 2005. The progression of the serve is described below in respect to the ground up transfer of energy: Feet >Legs >Hips >Torso >Shoulder >Elbow >Wrist >Racket >Ball. ■ Shoulder speed: Your shoulder speed starts from your legs during stride stance at the baseline. Shifting your weight from your front foot to your back foot moves the energy up to your knees and is built upon when your thigh muscles activate. This is winding up all that power to then move up your torso and builds as your trunk rotates, winding up the core leading to the shoulder. ■ Elbow speed: The shoulder speed transfers to two pieces of the serve making up your elbow speed. One is how you position your shoulder in the early phase of the swing. Your arm should be down and behind the hip and lower back, storing up the power from your legs. The second is the positioning of the arm in the later phase of the swing. Your arm should be at its maximal point away from the body with the inside of the arm facing away from you. ■ Wrist speed and racket positioning: The elbow speed allows the wrist to get its energy. All the power stored up from the previous steps transfers through the forearm as it straightens and the wrist turns, bringing with it the shoulder moving toward the body. ■ Racket speed: This is the final point where all your stored kinetic energy from all your body parts gets transferred to the ball allowing you to ace your opponent. Developing the links in your kinetic chain is essential to preventing injury and having a faster, stronger serve. If the kinetic chain is broken and there is more than a second of delay from one stage of movement to the next, the body loses about 55 percent of its stored energy (Wilson et al, 1991). Stored energy could be considered elastic, meaning the muscles are pre-loaded similar to stretching a Slinky. Losing this stored energy causes each individual body part in the kinetic chain to have increased stress and force. Wait. ... Is this why my shoulder hurts when I try to ace my opponent with my first serve? Well, if you have not been training your kinetic chain, most likely. When training for tennis, remember that about half of the force used to hit the ball comes from your big toe, legs, hips, trunk and core combined. What? My big toe? Yes, your power and energy transfers from the feet up. Do you need to do toe crunches? Well, no, but you do want to strengthen your lower body and core. ✪

Health Watch Caron Bush

Caron Bush is a physical therapist for the staff of Sports Medicine For Young Athletes, a division of Children’s Hospital Oakland with a facility also located in Walnut Creek. If you have a health-related question for the “Health Watch” column, write the Sports Medicine For Young Athletes staff at

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September 22, 2011



Issue 32, 09.22.2011