Tendons are another one of my favorite connective tissues - from both a physical therapy and performance perspective. Our tendons are critical in creating powerful movements and are especially important in jumping and sprinting; however, they are also a source of chronic pain and dysfunction in many athletes. With properly dosed loading, we can help ensure that our tendons stay healthy and strong- mitigating risk of injury and its subsequent impact upon training.
Tendons serve such an important role in our body by attaching muscles to bone, allowing for movement of our skeleton to occur. They are highly viscoelastic structures that transmit high loads from muscles, which allows them to pull on the bone to create movements at joints. They are incredibly strong structures composed of collagen and elastin, which allows them to stretch and shrink back with load. The Achilles tendon is the strongest in the body; this is necessary as 50% of our propulsion during running comes from our plantar flexors, or calf musculature.1
Tendinopathy is an umbrella term that describes degeneration of a tendon due to excessive overload to a tissue without adequate recovery. It encompasses the commonly (and often incorrectly) used term tendinitis, which refers to inflammation of the tendon itself. While this can sometimes be the case in acute, reactive tendon conditions, tendinopathy is a more appropriate term to use as pain, rather than inflammation, is used to clinically diagnose tendon conditions.2 The typical presentation of tendinopathy is pain that is initially present during exercise, but tends to decrease throughout the session. Tendons like to warm-up; the theory behind this is that once tenocytes (the cells in tendons) hit a certain threshold of activity, desensitization of ion-activated channels occurs. Thus, tendinopathies are often worse again first thing in the morning or upon starting a workout after tenocytes “reset”, but improve throughout the day and with increased duration of exercise. 3
Tendinopathies are common in the Achilles, rotator cuff, elbow, and hamstring. Structural changes in the tendon include thickening (aka tendinosis) and loss of collagen structure and organization2, which leads to a decrease in stiffness of the tendon - as counterintuitive as that may seem. For those of you who have experienced tendinopathy, while your tendon may feel stiff, the opposite actually occurs- in conjunction with decreased force production. Think of it like a giant, stretchy rubber band. If a tendon is too compliant, we won’t get as much force production and movement from the bone. There is, however, such a thing as too stiff; if our tendons are relatively stronger than our muscles, the muscle will take more of the load and be more susceptible to injury. This is often the case in individuals who are susceptible to muscle tears. Thus, there does exist a sweet spot; in the case of tendon pain, however, rehab should be focused on increasing stiffness.
Tendons have relatively poor blood supply compared to other tissues. During mechanical loading, a muscle contracts and puts tension on a tendon. As the muscle relaxes, the tendon is like a sponge- allowing synovial fluid containing nutrients to diffuse into the tendon.4 This also allows for lubrication of the tendon that facilitates smooth gliding during movement. 5 This highlights the importance of movement; when we rest our tendons, we provide it with no way to receive nutrients that are essential to healing. This is great news to all the endurance junkies out there who love training, as the absolute worst thing you can do to heal a tendinopathy is to stop activity altogether.
Instead, the key to tendon rehab is “relative” rest. Tendinopathies are the result of excessive load relative to that tendon’s strength/ capacity. While it is detrimental to engage in complete rest from activity, there is always some form of activity modification that needs to occur. This might mean decreasing to 50% of your normal running volume and cutting out intensity altogether while you engage in rehab exercises. In contrast to bone stress injuries, where any amount of pain is a red flag to stop activity, it is okay to continue training with minimal amounts of pain with tendinopathies. While the 0-10 pain scale has been criticized for its subjectivity, it actually serves as a great tool for tracking an individual’s pain levels on a day to day basis with training. The general rule of thumb is that as long as pain remains at about 3/10 and does not exceed 5/10 during activity and within the subsequent 24 hours, it is acceptable to continue training at that volume/ intensity. An increase in pain levels should also be monitored; if pain levels do not return back to baseline within 24 hours, then this is also an indicator that you are overdoing it and need to adjust training. This is important because response to loading can take up to 3 days to occur, meaning that pain during activity is not always the best indicator of whether or not we are “overdoing” it.6 In cases like tendinopathies, I recommend using an “injury log” to track daily symptoms and pain levels. This keeps us honest and gives light to any trends in training that may be spiking symptoms, and ultimately, setbacks.
From a rehab perspective, it is important to work with a Physical Therapist to determine the appropriate exercises/dosage that should be performed. However, resistance training in some capacity should be incorporated into rehab due to the way tendons receive nutrients, as previously explained. While plyometric activities are ultimately the best thing for tendons, as quick movements increase tendon stiffness and mimic sport-specific motions,7 they are often too painful in the acute phase of a tendinopathy.
That is why strengthening is a great starting place for rehab, and research has shown that tendons respond best to heavy, slow contractions. 2 This means lifting as much weight as possible, aiming for 3 sets of 6-8 reps (counting to 3 on the way down, and 3 on the way back up for each rep to take 6 seconds total). It has also been found that an increase in added load does not correlate to an increase in pain, meaning that we don’t need to be as cautious with adding weight to a single leg heel raise as transitioning to plyometric movements (like a single leg hop).8 While the type of contraction does not necessarily matter (i.e. concentric, eccentric, or isometric), isometrics, or long-hold contractions where the muscle does not change in length, have been shown to have an analgesic effect. This makes them a great option to perform prior to exercise.9 This could be done in the form of 5 x 30 second holds with 2 minutes rest in between prior to exercise, in addition to heavy loading in the gym 2x/week. If tolerated, 5-10 minutes of plyometric activity (i.e. jump roping, pogo jumps, box jumps) 3-4x/week is also a component of rehab. These can be progressed in terms of both load and jump height to facilitate full return to normal training loads.
Another way to maximize tendon rehab/health is through supplementation with gelatin or hydrolyzed collagen. Collagen is the main building block of connective tissues, and it serves as a scaffold for building tendons. Hydrolyzed collagen comes in a powder form and is easy to dissolve in a hot drink. While it can be taken at any point throughout the day, the ingestion of collagen prior to exercise/rehab provides our body with the building blocks to utilize during activities that stress the tendon. Research has shown that taking 10-20g of collagen combined with 5g of vitamin C (which is essential for collagen synthesis) one hour prior to exercise is effective in decreasing pain and accelerating healing/ rehab outcomes in patients with tendinopathies. 10,11
To nerd-out more about collagen structure and its multitude of other uses in the body, read this post by Sky!
In summary, key tips for dealing with tendinopathies or tendon related pain:
Perform isometric holds immediately prior to activity (i.e. 5 x 30 second bridge on heels for hamstring tendinopathy with 2 min rest between).
Ingest 10-20 mg of collagen with 5 g of vitamin C 1 hour prior to exercise.
Engage in relative rest- don't stop activity completely, but reduce volume/intensity to ensure that pain remains at about 3/10 and does not exceed 5/10 (including 24 hours after activity).
Add progressive resistance training 2-3x/week with emphasis on heavy, slow contractions. Add as much weight as possible, aiming for 3 sets of 6-8 reps. Count to 3 seconds on the way down, 3 seconds on the way back up for each rep.
Perform plyometric activities 3-4x/week (i.e. 5-10 min of jump rope or 3 x 10-15 reps of pogo jumps, box jumps, etc.). Keep in mind that quick motions are most irritable for tendons, so only add this in accordance to tip number 3.
Dissolve 10-20g collagen + 5 g vitamin C 1 hour prior to exercise to aid collagen synthesis!
Don't get discouraged if your tendon pain lingers for months; tendinopathies can take 12+ months to fully heal. Stick to your plan and trust the process- without proper rehab, its guaranteed to take even longer!
References:
1. Conner BC, Luque J, Lerner ZF. Adaptive Ankle Resistance from a Wearable Robotic Device to Improve Muscle Recruitment in Cerebral Palsy. Ann Biomed Eng. 2020;48(4):1309-1321. doi:10.1007/s10439-020-02454-8
2. Silbernagel KG, Hanlon S, Sprague A. Current Clinical Concepts: Conservative Management of Achilles Tendinopathy. Journal of Athletic Training. 2020;55(5):438-447. doi:10.4085/1062-6050-356-19
3. The Pain of Tendinopathy: Physiological or Pathophysiological? | Sports Medicine. Accessed May 15, 2024. https://link.springer.com/article/10.1007/s40279-013-0096-z
4. Fenwick SA, Hazleman BL, Riley GP. The vasculature and its role in the damaged and healing tendon. Arthritis Research & Therapy. 2002;4(4):252. doi:10.1186/ar416
5. Ray G, Sandean DP, Tall MA. Tenosynovitis. In: StatPearls. StatPearls Publishing; 2024. Accessed May 15, 2024. http://www.ncbi.nlm.nih.gov/books/NBK544324/
6. Grävare Silbernagel K, Crossley KM. A Proposed Return-to-Sport Program for Patients With Midportion Achilles Tendinopathy: Rationale and Implementation. Journal of Orthopaedic & Sports Physical Therapy. 2015;45(11):876-886. doi:10.2519/jospt.2015.5885
7. Ramírez-delaCruz M, Bravo-Sánchez A, Esteban-García P, Jiménez F, Abián-Vicén J. Effects of Plyometric Training on Lower Body Muscle Architecture, Tendon Structure, Stiffness and Physical Performance: A Systematic Review and Meta-analysis. Sports Med - Open. 2022;8(1):40. doi:10.1186/s40798-022-00431-0
8. Sancho I, Willy RW, Morrissey D, Malliaras P, Lascurain-Aguirrebeña I. Achilles tendon forces and pain during common rehabilitation exercises in male runners with Achilles tendinopathy. A laboratory study. Phys Ther Sport. 2023;60:26-33. doi:10.1016/j.ptsp.2023.01.002
9. Rio E, van Ark M, Docking S, et al. Isometric Contractions Are More Analgesic Than Isotonic Contractions for Patellar Tendon Pain: An In-Season Randomized Clinical Trial. Clinical Journal of Sport Medicine. 2017;27(3):253. doi:10.1097/JSM.0000000000000364
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