Benefits of Isometric Loading for Tendon Pain and Dysfunction

Benefits of Isometric Loading for Tendon Pain and Dysfunction

Because tendons are subjected to repetitive loading during sports and exercise, tendon pain and dysfunction are common complaints among athletes and physically active populations. Isometric muscle contractions and eccentric loading have long been favored as treatments of choice by sports physical therapists, to manage tendon pain and improve function.

New research gives us greater insight into the benefits of isometric loading, and how isometric exercises promote tendon healing. We also understand more about the most effective isometric loading protocols in terms of intensity, duration, frequency and exercise selection.

Dynamic vs Isometric Muscle Contractions

Voluntary muscle contractions occur when a motor neuron delivers a message from the brain that sets a reactive impulse in motion. Each motor neuron is responsible for exciting a given number of muscle fibers. The motor neuron and the fibers associated with it are collectively referred to as a motor unit.

Each motor unit functions according to the all-or-nothing principle, meaning that each impulse from the motor neuron elicits a contractile response in all its associated muscle fibers, at the same time. During isometric contraction exercises, the motor units involved produce a consistent amount of contractile force, called torque, throughout the duration of the exercise.

Dynamic vs Isometric Muscle Contractions

One of the most popular exercises to illustrate isometric muscle contraction is the plank. During this highly effective total body exercise, your muscles develop a high level of tension without the muscle fibers changing length, and without a change in joint angles. By contrast, dynamic exercises require dynamic changes in muscle length and joint angles to produce movement.

Unlike isometric exercises that have a single phase, dynamic contractions take place in two phases. In the concentric phase, muscle fibers shorten as they produce adequate torque to overcome the force of gravity, and joint angles become smaller. In the eccentric phase, the muscles lengthen as the fibers continue to exert force, but at a torque slightly less than the force of gravity, as joint angles grow larger.

Dynamic vs Isometric Muscle Contraction

Eccentric Loading vs Isometric Muscle Contractions

Both eccentric loading and isometric strengthening exercises are used to treat tendon pain, promote healing, and restore strength and function. While many studies have compared the relative effectiveness of the two, they are often used in tandem during tendon rehabilitation.

Factors that influence tendon loading rehab protocols include:

  • The unique health profile of the patient
  • The sports or activities that the patient engages in
  • The location and architecture of the injured tendon
  • The severity of damage to the tendon
  • The degree of tendon stiffness
  • The relative strength of the tendon and its associated muscle
Eccentric Loading vs Isometric Muscle Contractions

The body of research on tendon loading protocols for treating tendinopathies is extensive and growing. Many recent studies compare various approaches to tendon loading and testing.

  • A new 2021 study by Alessandro et al. looked at shear wave elastography (SWE) and strain elastography (SE) as methods for testing tendon elasticity under isometric load, and found both to be effective for measuring tendon stiffness.
  • A 2020 study by Contento et al. found that residual isometric torque was most effectively enhanced following an active eccentric contraction, with increased tendon-evoked activation of the golgi tendon organ (GTO).
  • In another study (Pearson et al. 2020), researchers found isometric muscle contractions to be effective for alleviating patellar tendon pain during a single-leg decline squat test and a single-leg hop test, with improved quadricep function over a 4-week isometric training period.
  • Gatz et al. (2020) found no difference in outcomes for Achilles tendinopathy when isometric contractions were combined with eccentric contractions over a 3-month training intervention, but they did find that shear wave elastography (SWE) was able to distinguish between the elastic properties of the insertional portion of the tendon and the midportion, which is important for gauging the degree of tendon pathology.
  • In a 2018 peer-reviewed paper, Mascaro et al. offer a load management protocol for tendinopathy rehab that involves a progression of exercises, beginning with isometric therapy, followed by tendon strengthening exercises for functional strength, speed, and jumping exercises, to gradually restore the tendon’s ability to store and release energy.

Working Out With Tendinitis

Working Out With Tendinitis

If you are in the habit of working out on a regular basis, you may find it difficult to take time off to heal a sore and inflamed tendon. But failing to allow your tendons ample time for recovery can be a serious mistake. Unlike muscle tissue that is highly vascular, tendons are made up mostly of collagen and have a limited number of blood vessels.

When tendons are injured, their low vascularity means that the delivery of oxygen and nutrients needed for healing is restricted. Over time, placing repetitive demands on an injured tendon can cause its collagen matrix to deteriorate even further, a condition called tendinosis. Unless you take proactive measures to reverse the process and heal the tendon, you could end up with a dysfunctional tendon that inhibits your ability to exercise or play sports.

High Tech Equipment for Accurate Tendon Diagnosis and Testing

Accurate diagnosis is fundamental to establishing a baseline and designing a personalized treatment program to promote tendon healing. Once treatment is underway, technological tools help us test the patient’s progress, to ensure our treatment is effective.

Tools for tendinopathy diagnosis and testing include:

  • Diagnostic ultrasonography, to view the damaged tendon in real time, with the patient in motion.
  • Sonoelastography, to test the tendon’s mechanical properties of elasticity and stiffness.
  • Superior microvascular imaging, to detect early vascular activity that indicates the healing process is underway.
High Tech Equipment for Accurate Tendon Diagnosis and Testing

Advanced technologies enable us to precisely measure the patient’s progress, eliminating guesswork and ensuring that the patient is fully healed before they return to full activity.

Advanced Tendon Treatment Options Bring Optimal Results

At NYDNRehab, we embrace the latest technologies to bring 21st Century treatment options to our patients. High-tech equipment allows us to precisely measure your progress, so we know without a doubt when it is safe for you to return to your active lifestyle.

  • Blood Flow Restriction Therapy lets us provide the most evidence-based loading protocols without doing further damage to injured tissues.
  • DD Robotech brings artificial intelligence into the rehab space, providing feedback retraining that restores the pathways between your brain, muscles and tendons.
  • Proteus Co-Linear Resistance promotes skills enhancement and retraining, so you can bring your best game to the field when you return to sport.
  • C.A.R.E.N., our computer assisted rehabilitation environment, gives us a broad range of options for testing, loading and retraining injured tendons.
 Advanced Tendon Treatment Options Bring Optimal Results
  • Ultrasound assisted muscle activation uses ultrasonography to help the patient visualize the muscle and activate it, to retrain optimal firing patterns that often become altered after a tendon injury.
  • Ultrasound guided dry needling to eliminate trigger points, tiny knots of myofascial tissue that often occur near the musculotendinous junction, causing pain and dysfunction.
  • Redcord Therapy takes isometric training to a new level by incorporating elastic resistance and suspension.
  • Extracorporeal shock wave therapy and electromagnetic transduction therapy are regenerative technologies used to stimulate tendon healing at the cellular level.

Getting the Bigger Picture

Exercise selection and mode can both make a difference in the effectiveness of your tendon rehab program, in accelerating your recovery and restoring full function. However, that is only one small part of the total equation.

For the quickest tendon rehabilitation with the highest likelihood of returning you to full activity, you need the following elements:

  • A knowledgeable sports physical therapist who understands tendon pathologies and how to heal them.
  • Accurate diagnosis, preferably using real-time imaging, to ensure that the extent and severity of your tendon pathology is completely understood.
  • Access to advanced technologies that can help you restore optimal neuromuscular pathways and measure your progress.

Isometric Therapy and Tendon Strengthening Exercises at NYDNRehab

Training with an injured tendon can cause it to deteriorate, potentially taking you out of the game for good. To accelerate healing and restore tendon function, you need advanced treatment methods that cannot be found in most physical therapy clinics.

/At NYDNRehab, we design personalized treatment plans based on your unique diagnosis, and we measure your progress every step of the way. We know that rehabilitation is time consuming, and we believe that time should not be wasted. Contact us today, and heal your injured tendon so you can get back to your favorite sport or activity.


  • Alessandro, Schneebeli, et al. “Shear wave and strain sonoelastography for the evaluation of the Achilles tendon during isometric contractions.” Insights into Imaging 12.1 (2021).
  • Contento, Vincenzo S., Brian H. Dalton, and Geoffrey A. Power. “The inhibitory tendon-evoked reflex is increased in the torque-enhanced state following active lengthening compared to a purely isometric contraction.” Brain sciences 10.1 (2020): 13.
  • Gatz, Matthias, et al. “Eccentric and isometric exercises in Achilles tendinopathy evaluated by the VISA-A score and shear wave elastography.” Sports Health 12.4 (2020): 373-381.
  • Mascaró, Alfons, et al. “Load management in tendinopathy: Clinical progression for Achilles and patellar tendinopathy.” Apunts. Medicina de l’Esport 53.197 (2018): 19-27.
  • Pearson, Stephen J., et al. “Immediate and short-term effects of short-and long-duration isometric contractions in patellar tendinopathy.” Clinical Journal of Sport Medicine 30.4 (2020): 335-340.

In this instance, an athlete was originally diagnosed with minor quadriceps muscle strain and was treated for four weeks, with unsatisfactory results. When he came to our clinic, the muscle was not healing, and the patients’ muscle tissue had already begun to atrophy.

Upon examination using MSUS, we discovered that he had a full muscle thickness tear that had been overlooked by his previous provider. To mitigate damage and promote healing, surgery should have been performed immediately after the injury occurred. Because of misdiagnosis and inappropriate treatment, the patient now has permanent damage that cannot be corrected.

The most important advantage of Ultrasound over MRI imaging is its ability to zero in on the symptomatic region and obtain imaging, with active participation and feedback from the patient. Using dynamic MSUS, we can see what happens when patients contract their muscles, something that cannot be done with MRI. From a diagnostic perspective, this interaction is invaluable.

Dynamic ultrasonography examination demonstrating
the full thickness tear and already occurring muscle atrophy
due to misdiagnosis and not referring the patient
to proper diagnostic workup

Demonstration of how very small muscle defect is made and revealed
to be a complete tear with muscle contraction
under diagnostic sonography (not possible with MRI)


Complete tear of rectus femoris
with large hematoma (blood)


Separation of muscle ends due to tear elicited
on dynamic sonography examination

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