In men aged 69–70, performing supervised slow resistance training three times a week for 12 weeks leads to a small but measurable increase in the thickness of the patellar and Achilles tendons.

We analyzed two assertions about slow resistance training and tendon size in older men, and both support the idea that this type of training can lead to small increases in tendon thickness. In men aged 69 to 70, doing supervised slow resistance training three times a week for 12 weeks was linked to a measurable, though small, thickening of the patellar and Achilles tendons [1]. A second assertion found the same result when the training used moderate to heavy weights, suggesting the effect may occur regardless of whether the load is light or heavy, as long as the movement is slow and controlled [2]. These findings come from studies that tracked tendon changes using imaging, and the increases observed were not large—but they were consistent and detectable. Slow resistance training means lifting weights with a deliberate, controlled motion, often taking several seconds to lift and lower the weight, which may place steady stress on tendons over time. The patellar tendon connects the kneecap to the shinbone, and the Achilles tendon connects the calf to the heel; both are critical for walking, standing, and moving safely as we age. We don’t know if these small changes improve function or reduce injury risk, because the evidence we’ve reviewed doesn’t measure those outcomes. We also don’t know if the same results would appear in women, younger men, or people with existing tendon issues. The studies we looked at were limited to healthy older men, and the training was always supervised, which may not reflect how most people train at home. What we’ve found so far suggests that slow resistance training may help maintain or slightly increase tendon size in older men. For someone looking to stay active and mobile, this could be one reason to include controlled, deliberate strength movements in their routine—even if the changes are small.