Mechanisms for ruptured Achilles tendons: women's gymnastics

The purpose of this study was to characterize the unusual take-off techniques demonstrated during tumbling take-offs on a spring tumbling strip (STS) and to assess the potential causes of these techniques and their possible contributions to Achilles tendon ruptures. A survey study of women’s collegiate gymnasts showed an alarmingly high 17.2% prevalence of ruptured Achilles tendons (Bonanno, Cheng, Tilley, Abutalib, & Casey). Twelve highly trained female gymnasts from USA Gymnastics voluntarily participated. The take-off was captured (2D) via high-speed video (500 fps). An accelerometer (1D) was placed under the STS take-off position (1000 Hz). Reflective markers were placed on the toes, heels, ankles, knees, hips, torso center, shoulders, elbows, wrists, hands, and the apices of the head. Lower extremity angles were of primary interest. Two take-off trials were cross-correlated and analyzed. Results indicated an unusual and unexpected “secondary knee flexion” during take-off. Knee angle changes indicated that take-off actions were not simple eccentric knee flexion followed by concentric knee extension. The observed motions are heretofore undocumented. During the period from heel contact to heel departure, the gymnasts’ ankles reach extremes of dorsiflexion at approximately the same time that their knees are extending, and the STS reaches its lowest position of descent. We speculate that the gymnasts may be readjusting muscle stiffness, reacting to a sudden intermediate vibration of the STS, or showing an artefact of the rearward rotation of the entire body about the feet. The observed actions may contribute to Achilles tendon injury.