| | | Tendinopathy: Isotonics Rehab

Author / Matthew Zanis

7 - 12 minute read

Have you ever been to rehab for a patellar or Achilles tendinopathy injury before and felt like a hamster on the proverbial wheel? You show up, check in, then receive the same passive treatments of ice, heat, massage, and stretching you have done in your living room with the same bullshit 3 sets of 10, day in and day out. Feel like rehab-Groundhog Day to anyone? You may have even been given some isometrics that provided pain relief. The pain may have gone away, and won’t treatments stop there; where the real work actually begins.  And believe it or not, there is still a chance you can recover from this injury and be back to your old self!

Isometrics, while useful, only get us part of the way towards our goals. The real, long term outcomes are achieved through a Power Athlete staple – strength training! In this article on tendinopathies, we will discuss how to use Isotonics and Heavy Slow Resistance Training (HSRT) to achieve long term success.


You’ve successfully helped reduce your pain with a smart dose of concentrated isometrics, but now it’s time to build up that tendon! Typically, rehab professionals have relied on controlled eccentric exercise (aka lengthening of the muscle being worked) to facilitate restrengthening the tendon, but more recent evidence points to improved outcomes by also incorporating the concentric portion of movements (aka shortening of the muscle being worked); (1,2,4) This type of controlled rehabilitative movement is referred to as an isotonic muscle contraction. No, it’s not some type of fancy cocktail made with gin; it’s a muscle contraction where the concentric and eccentric portion are performed at a constant tension. (1)

The chief aim of this type of exercise is to develop strength in the tendon AND the associated muscle, in order to improve the balance between the two. In an isotonic contraction, the muscle fibers are contracting with the same force during the eccentric portion of a lift as they are during concentric portion.(1) They are contracting ferociously so that the middle portion (myotendinous junction) doesn’t “rip” apart.

The heavy weight and slow repetitions are utilized to load the tendon, signaling it to make new, more robust tendon tissue in the myotendinous junction, effectively strengthening the once weak and imbalanced area of the tendon where the injury occurred. (5,6)  In contrast, explosive, rapid loading, or ballistic type movements like plyometrics should be avoided since they are what usually cause the tendon problem to develop in the first place.

Treat the Doughnut, Not the Hole

Tendons adapt to load in the postures and positions where they experience the greatest stress. Stress is the language our cells speak, and this language can stimulate both positive and negative reactions.(7,9) This is part of what makes strength training different than unloaded human movement; whatever the joints are doing, the muscles and tendons will respond accordingly. For example, if we set the joints up in a mechanically efficient toes forward position (aka the UAP), we can let the muscles and tendons do their thing because they are in the best position to absorb load and reduce force.(8) This setup then creates a positive eustress environment for the tendon to adapt.

It is important to understand that we are not trying to change the part of the tendon you already damaged with your shitty movement patterns or egocentric training strategy. Once the tendon is disrupted beyond a certain threshold, the involved region loses its ability to transmit load.(5,7) No amount of mechanical stimulus, especially not from any fancy “scraping” tool or cupping, can force change.

However, this isn’t all doom and gloom. We DON’T need change to occur at the site of degeneration. There is redundancy within the tendon. Your body is smart, even if you are not. It increased the percentage of disorganized tissue (why you might be told your tendon has thickened) as a way to improve its load bearing capacity. Along with this, we can still evoke change in the areas of perfectly good, aligned collagen with strength training. Think of this as treating the doughnut instead of the hole. (3) Your tendon will now come back bigger AND stronger than ever before!

More is NOT Better

While strength training to repair your previously damaged tendon sounds fun and exciting, you should not load beyond your ability to adapt. We need optimal tissue loading to produce a desired response (overload) in a range that stresses the particular area of the involved tendon (specificity), while still allowing for the tissue remodeling process to occur with adequate recovery. (9,10) We need to find the sweet spot where total stress is enough to disrupt tissue balance and create an impetus for change, without diminishing the structural integrity of the undamaged tendon.

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How do we know how much load is just right? Well, we can’t rely on pain because we know that pain is a protective mechanism for the body and not simply a reflection of the state of your tissues. Don’t panic if you experience low levels of pain while performing these exercises; as long as it doesn’t exceed 3-4 on a pain scale or last for days afterwards, we are on the right track. We follow principles for rehabilitating tendinopathies, but just like strength and conditioning, we each have a unique set of limiting factors and tolerance to load that need to be accounted for. This is where finding a trusted rehab professional comes in handy.

Master Your Movement: Reload to Repair

Complex problems are usually solved by simple interventions. Don’t over complicate this! Progressively overload the tendon each week and ensure adequate recovery between sessions to produce optimal strength and resiliency adaptations. Want to learn the nuts an bolts on how to do this correctly? Set up a Remote Coaching program with Physical Therapist and Power Athlete Block One Coach, Dr. Matt Zanis to get you on the right track with an individualized program designed to get you off the bench and back on the starting line.

Related Content

EDU: Power Athlete Methodology
BLOG: Tendinopathy – Isotonics Rehab Part 2 by Dr. Matt Zanis
PODCAST: Power Athlete Radio Ep. 274 w/ Cal Dietz – Strong Feet, Strong Butt
PODCAST: Power Athlete Radio Ep. 352 w/ Dr. Keith Barr – The Future of Muscle Tissue
BLOG: Triphasic Training on Field Strong’s French Contrast Cycle by Tex McQuilkin


  1. Bavelloni A, Piazzi M, Raffini M, Faenza I, Blalock WL. Prohibitin 2: At a communications crossroads. IUBMB Life. 2015;67(4):239-54.
  2. Bohm S, Mersmann F, Arampatzis A. Human tendon adaptation in response to mechanical loading: a systematic review and meta-analysis of exercise intervention studies on healthy adults. Sports Med Open. 2015;1(1):7
  3. Docking S, rosengarten S, Daffy J, cook J. Treat the donut, not the hole: The pathological achilles and patellar tendon has sufficient amounts normal tendon structure.Journal of Science and Medicine in Sport. 2014;18:e2.
  4. Dunn SL, Olmedo ML. Mechanotransduction: Relevance to Physical Therapist Practice-Understanding Our Ability to Affect Genetic Expression Through Mechanical Forces. Phys Ther. 2016;96(5):712-21
  5. Kösters A, Wiesinger HP, Bojsen-møller J, Müller E, Seynnes OR. Influence of loading rate on patellar tendon mechanical properties in vivo. Clin Biomech (Bristol, Avon). 2014;29(3):323-9
  6. Magnusson SP, Langberg H, Kjaer M. The pathogenesis of tendinopathy: balancing the response to loading. Nat Rev Rheumatol. 2010;6(5):262-8
  7. Roberts TJ, Konow N. How tendons buffer energy dissipation by muscle. Exerc Sport Sci Rev. 2013;41(4):186-93
  8. Schoenfeld BJ. Squatting kinematics and kinetics and their application to exercise performance. J Strength Cond Res. 2010;24(12):3497-506
  9. Sharma P, Maffulli N. Tendon injury and tendinopathy: healing and repair. J Bone Joint Surg Am. 2005;87(1):187-202
  10. Thorpe CT, Screen HR. Tendon Structure and Composition. Adv Exp Med Biol. 2016;920:3-10
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Matthew Zanis

PT, DPT, FAAOMPT, OCS, ATC, CSCS Former baseball catcher and an avid outdoorsman. Worked with Division 1 basketball, football, and track and field at the University of Pittsburgh, along with the Pittsburgh Pirates and Arizona Cardinals organizations. Received a Bachelors in Athletic Training from the University of Pittsburgh in 2011 and a Doctorate in Physical Therapy from Duke University in 2014. Is board certified in Orthopedics and a Fellow through the American Academy of Orthopedic Manual Physical Therapists. Is a PT with the United States Olympic Committee and USA Shooting. Currently operates his performance therapy practice in Scottsdale, AZ with Dr. Tom Incledon of Causenta Wellness, and became a Power Athlete Block One Coach in September of 2017.

Dr. Zanis utilizes the Power Athlete Methodology to optimize performance, reduce injury risk, and rehab his clients and athletes through movement assessment, coaching, and individualized program design.

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