Increased cross-sectional area and reduced tensile stress of the Achilles tendon in elderly compared with young women

Abstract

The Achilles tendon cross-sectional area (CSA), tensile force, and stress during an isometric contraction were examined in healthy young (n = 9, age = 29 ± 1 years, mean ± SEM and elderly (n = 10, 79 ± 2 years) women. CSA area was obtained with magnetic resonance imaging 3 cm proximal to the insertion, and tendon force was obtained from the isometric ankle moment. The moment of force about the ankle joint was greater in young women (95 ± 17 N m) than in elderly women (51 ± 5 N m; p < .05). The Achilles tendon CSA was significantly greater in elderly women (56.3 ± 3.0 mm2) than in young women (46.0 ± 1.9 mm2; p < .01). These data show that young women can exert a greater force than elderly women on the Achilles tendon during voluntary contraction, although elderly women have an increased (22%) tendon CSA, and a lower tendon force than young women. The greater tendon size combines to lower the stress on the tendon markedly, which may reduce the risk of injury to the tendon.