Eccentric loading for tendons

A tendon is the thick rope that connects muscle to bone, and every sprint, jump, and cut asks that rope to store force and give it back a split second later. When the load goes up faster than the tendon can adapt, pain usually shows up first in places like the Achilles tendon at the heel or the patellar tendon below the kneecap. (jospt.org) That is why tendon rehab now starts with loading, not with the idea that the tendon needs complete rest. The 2024 clinical practice guideline for midportion Achilles tendinopathy says clinicians should use tendon-loading exercise as a first-line treatment, with loads as high as tolerated, to improve function and decrease pain. (apta.org) Eccentric loading is one specific way to do that job. It means the muscle is working while it lengthens, like lowering your body down from a calf raise or controlling the descent of a squat instead of just pushing back up. (wexnermedical.osu.edu) The reason clinicians like the lowering phase is simple: it lets you put meaningful force through the tendon in a controlled way. That controlled stress is the signal the tendon uses to rebuild capacity, much like a callus forms after repeated friction instead of after one giant blister. (wexnermedical.osu.edu) The old fear was that pain during rehab meant damage. The pain-monitoring model used in tendon programs allows some pain during exercise, often up to 5 out of 10, as long as it settles after the session and is not worse the next morning. (jospt.org) That is where the “24-hour rule” comes from. If pain or morning stiffness is the same or better 24 hours after loading, the tendon usually tolerated the session well enough to keep progressing. (physio-pedia.com) The exercises are not random. A typical Achilles program starts with heel rises using both legs, then moves to single-leg work, then adds a step for more range, then adds a backpack or machine for heavier resistance, and only later brings back fast rebounding and jumping. (jospt.org) This also explains why injections and surgery are no longer the automatic next step for most athletes with tendon pain. A randomized trial in patellar tendinopathy found that progressive tendon-loading exercise produced better clinical outcomes at 24 weeks than eccentric exercise therapy alone, which pushed the field toward broader progressive loading rather than quick procedural fixes. (bjsm.bmj.com) Eccentric work still matters because it was one of the first loading methods to show that tendons can improve under stress instead of only under protection. A recent scoping review of 31 studies in athletes found eccentric training consistently improved pain and function, with pain monitoring built into many of the protocols and few adverse events reported. (jssm.org) The catch is time. Tendons usually change more slowly than muscles, and rehab programs commonly run for 6 to 12 weeks before athletes notice clear gains, with some return-to-sport progressions stretching from 12 weeks to 6 months. (physio-pedia.com) (jospt.org) So the current playbook is not “rest until it disappears” and not “push through anything.” It is measured loading, small pain, next-day recovery, and gradual heavier work until the tendon can handle the same forces that sport demands. (apta.org) (physio-pedia.com)