Engineered Ligaments and the Minimal Effective Dose of Tendon Load

Keith's lab grows ligaments from cells taken from ruptured human ACLs and loads them in a small robot. The adaptive signal peaks by about 10 minutes of loading; anything beyond that adds wear without more signal. A second bout two hours later gives only part of the response, while waiting six hours restores it fully. Ten minutes of stretch every six hours produced an eightfold rise in collagen, twice that of continuous loading. With equal time under tension, four 30-second isometric holds with two minutes of rest gave higher failure load and collagen content than dynamic loading, with less wear. The idea reached rock climbing through the Abrahamsson brothers, who hung about 40% of body weight from their fingers for 10 minutes. Data from climbers using a training app showed that both these low-intensity hangs and maximal hangs raised grip strength, and combining them had an additive effect, likely because they target tendon force transfer and muscle separately.