In healthy men aged 69–70, 12 weeks of supervised slow resistance training increases the stiffness and elastic properties of the Achilles tendon and the muscle tissue connecting the quadriceps to the...

We analyzed two studies on slow resistance training in elderly men and found that both support the idea that this type of training can increase stiffness in certain tendons and connective tissues. After 12 weeks of supervised, slow strength training, healthy men aged 69–70 showed greater stiffness in the Achilles tendon and the tissue connecting the quadriceps to the knee, meaning these structures resisted deformation more under force [1]. The same training did not change stiffness in the tendon below the kneecap or the calf muscle tissue, suggesting the effect is specific to certain areas [2]. In another study, similar results were seen: increased force and stress in several leg tendons, with only the Achilles and part of the thigh’s connective tissue becoming stiffer [1]. No studies in our review showed a decrease or lack of change in these tissues under the same conditions. What we’ve found so far leans toward slow resistance training improving stiffness in some, but not all, tendons and connective tissues in older men. The changes appear targeted — not universal — and may depend on which muscle-tendon unit is being trained. This doesn’t mean every tendon gets stronger, but key ones involved in walking and standing may become more resilient. For older men looking to support movement and reduce injury risk during daily activities, slow, controlled strength training may help stiffen the tendons that matter most for stability and power.