Mechanical Properties of Human Tendon and Their Age Dependence

Abstract

There are no previously published data on changes in the mechanical behaviors of human tendon from maturation in the second decade to senectitude in the seventh decade or thereafter. In this study, 44 tendons from individuals ranging in age from 16 to 88 yr were subjected to an extensive series of mechanical tests which included preconditioning, extensions at strain rates of 100 percent/s, 1 percent/s, and 0.01 percent/s, and stress relaxation with cyclic and constant extensions. Pairs of extensions at 1 percent/s were run throughout the protocol to evaluate the repeatability of tissue response. It was found that these responses changed little for any single sample within a pair of such tests; however, throughout the protocol, the peak stresses and moduli decreased. Extensions at different rates revealed a definite rate dependency of tendon responses with sample modulus being directly related to extension rate and slightly less hysteresis at 1 percent/s than at 100 percent/s or 0.01 percent/s. The load relaxation in samples subjected to either cyclic or constant extensions was generally best described by a linear function of the logarithm of time. The rate of relaxation with constant extension varied little with extension magnitude. The rate of relaxation in the cyclic tests was greater at 10 Hz than at 0.1 Hz. The results indicate that subject age has no effect on tendon modulus and a very small effect on hysteresis and relaxation. Extensive information on subject history was not available in this study for correlation with mechanical responses so that an age effect may have been masked by other variables, possibly health, diet, disease, or exercise.

Strength training alters the viscoelastic properties of tendons in elderly humans

“…12,21,49,50 Our estimate, however, is higher than the average mechanical hysteresis value of ϳ10% reported from measurements on adult mammals. 5,25,45 This discrepancy may be accounted for, in part, by aging-induced increases in the mechanical hysteresis of tendon.…”

“…5,25,45 This discrepancy may be accounted for, in part, by aging-induced increases in the mechanical hysteresis of tendon. 21 Moreover, our in vivo method cannot exclude friction of the tendon and the patella as they pass over internal structures, such as the fat-pad lying posterior to the patella tendon. Internal friction is likely to oppose tendon recoil and result in overestimation of hysteresis as compared with in vitro conditions.…”

On the independence of time and strain effects in the stress relaxation of ligaments and tendons

“…In some studies it has been shown that the strain levels in#uenced the relaxation of the stress (Haut and Little, 1972;Lanir, 1980), while in other works, only slight strain dependence has been found for the relaxation modes (Hubbard and Soutas-Little, 1984;Soden and Kershaw, 1974). The necessary experiments have not yet been done for ligament tissues (Lakes and Vanderby, 1999).…”

Favorable Outcome of Percutaneous Repair of Achilles Tendon Ruptures in the Elderly

“…One study suggests that aging produces stiffer and stronger tendons [50], but other investigations led to the opposite conclusion [44,54] or showed no effect of aging on most of the mechanical properties of the tendon [16]. In animals, tenocyte metabolism changes with increasing age [13], and these changes are accompanied by morphologic changes [6].…”