Tendonitis Revisited
An Isometric Protocol
“Nothing is certain except death, taxes and tendonitis.”
-The aging athlete.
Tendon injuries have a way of interrupting life. They don’t just impact your sport; they remind you how much you rely on even the simplest movements, picking up a coffee mug, carrying groceries, etc. . Whether it’s sharp pain during a workout or an ache that lingers long after, it’s clear these kinds of injuries need more than just rest to properly heal. Recovery starts with knowing the right way to load an injured tendon.
Tendons - Function and Injuries
Tendons are connective tissue bands, primarily type I collagen, linking muscles to bones. They act as force conduits, allowing muscles to drive bone movement by relaying contractile energy. For instance, the Achilles tendon joins calf muscles to the heel, enabling walking and running. Tendons also store elastic energy, enhancing efficiency in motions like jumping. When you bend at the hips, knees, and ankles before leaping upward, tendons capture tension from stretched muscles, releasing it to propel the jump.
Tendon injuries, whether from sports or everyday movement, result from collagen fiber damage. Common types include:
• Tendinopathy: Overuse leads to microtears or collagen degradation, causing pain and tissue breakdown. Examples are Achilles tendinopathy and lateral epicondylitis (tennis elbow). The term “tendonitis” is now less used, as inflammation isn’t always primary.
• Strains or Tears: Sudden overstretching or excessive force partially or fully ruptures collagen, as in rotator cuff tears or Achilles ruptures.
• Degenerative Changes: Aging or prolonged overuse weakens collagen structure, increasing injury risk, such as spontaneous quadriceps tendon tears.
Some tendon injuries arise from a single overload, triggering acute tears or ruptures. Most, however, develop slowly as collagen fibers deteriorate. When fibers weaken, the tendon shifts force to stronger areas, shielding damaged ones. While this seems protective, it can block healing by limiting stress to injured fibers. Recovery requires controlled loading to stimulate repair, ensuring force reaches the affected area.
For physical therapists, the traditional strategy for treating tendonitis involves using eccentric exercises to apply the appropriate level of force for healing.
Eccentrics
Eccentric exercises, think slowly lowering a weight that you just flexed or extended up with your wrist, is a long standing physical therapy approach to healing the epicondylitis maladies (golfer’s elbow and tennis elbow) or other instances of tendinopathy. This approach works, as studies show improvement in 60-90% of patients, depending on the study, protocol and area of the body being addressed.
I was taught in Physical Therapy school, and by clinical instructors that eccentric exercises are the most appropriate approach for addressing tendinopathy injuries. I have used this approach to varying degrees of success on both my patients and myself. It was thought that the slow motion of eccentrics coupled with the lengthening of the muscle (vs. concentric contractions which shorten the muscle), were the mechanisms by which this approach worked.
Research by Dr. Keith Baar at UC Davis has clarified the mechanistic healing effects of eccentric exercises, showing that the benefit does not stem from muscle lengthening. Instead, healing arises from tendon fatigue caused by the slow execution of the movement. When performed slowly, the motion fatigues the tendon, disrupting the protective mechanism that diverts force to stronger tendon regions. As a result, the injured area (affected by tendinopathy) begins to bear the force, signaling the body to initiate healing in the tendon rather than merely forming scar tissue.
Dr. Baar has shown that having any movement at all in the motion will inhibit, at least to some extent, the body’s signal to heal the tendon and as a result, recommends isometric exercises, not eccentrics.
Isometrics
Isometric exercises involve maintaining a static position without movement, such as holding a weight steady or staying in a squat. You’re not pushing or pulling here; you’re simply staying in place and letting your muscles contract gently. This type of exercise distributes the effort across the tendon more evenly, helping it rebuild while keeping the pain level manageable. It also reduces stress on the injured parts, which is a huge part of why they’re so effective early on in recovery.
General Isometric Rehab Protocol
Select exercises tailored to the injured tendon, following Dr. Keith Baar’s isometric protocol (Baar, 2014). For knee tendon pain, hold a wall squat at a 90-degree angle. Grip holds or static wrist holds work for elbow tendinopathy. Achilles injuries benefit from ankle holds—pressing your foot against resistance without moving. Keep joints mid-range, not fully bent or stretched, to minimize stress and promote healing.
Begin with short holds (10–15 seconds) if pain is severe, as Dr. Baar advises, progressing to 4 sets of 30-second holds with 2-minute rests (Baar, 2014). Use 60–70% of maximum effort, ensuring pain stays stable or eases. Perform 2–3 sessions daily, spaced 6–8 hours apart, for optimal tendon response. Each 5–10-minute session builds progress. Pain often decreases within weeks, but collagen repair takes months, requiring patience for lasting recovery.
Nutrition
What you eat also plays a significant role in the healing process. Tendons thrive on collagen, which forms the basis of the connective tissue. You can help your body produce more by taking simple steps like consuming gelatin with vitamin C. Studies show this combination can significantly boost the collagen repair process, especially when consumed around 30 minutes before doing isometric exercises. Imagine mixing unflavored gelatin into a glass of orange juice. The vitamin C helps the collagen fibers bond more effectively, directly supporting the work your exercises are doing.
Protein is your other big ally here. It’s essential for tissue repair in general, but many people don’t realize how important timing and consistency are. Include about 20 grams of protein with each meal, and spread those meals out through the day to get the most out of them. Whether it’s eggs, chicken, fish, or a good-quality protein shake, regular intake can support your body as it rebuilds.
Pitfalls
While you’re making these positive changes, it’s equally important to avoid certain pitfalls. No matter how tempting it may be, complete rest is rarely the answer. Tendons need movement to heal properly. Too much immobility can lead to stiffness, scar tissue, or even a decline in function over time. That doesn’t mean jumping back into high-impact activities either. Running, jumping, or heavy lifting too soon can overload the injured area and slow everything down.
Another common misstep is leaning too heavily on anti-inflammatory drugs or icing strategies. Yes, they can reduce pain temporarily, but they also suppress the inflammation your body uses to trigger the healing process. Using them sparingly, and only for short periods when the pain is unbearable, allows the natural process of repair to work more effectively.
Tracking your progress makes all the difference. Pay attention to how your pain behaves during daily activities. Does gripping a mug feel easier? Can you climb stairs without any tenderness? These small wins are markers that healing is happening. If something feels off or stays inflamed for over 24 hours after you exercise, scale back and give yourself time to adjust.
Recovery isn’t a straight line. Tendons heal over timelines that can stretch into months or, in severe cases, even a year or longer. What’s vital is staying consistent. Progress will come in phases. Early on, you’re simply getting the pain under control. As time passes, your holds will get stronger and longer, your pain will subside, and you’ll find yourself ready for more advanced movements.
This approach is supported by research, including findings from what’s called the Baar Protocol, which demonstrates how isometric exercises and targeted nutrition can support tendon repair. But fundamentally, the principles boil down to smart loading, thoughtful nutritional support, and avoiding practices that can hinder healing.
With consistency, it’s possible not only to get back to where you were but to emerge from rehabilitation stronger than before. Recovery takes time, but with the right tools, it’s entirely within your reach.