The Acute Effect of Isometric Versus Isotonic Resistance Exercise in Patients With Patellar Tendinopathy

The purpose of this study is to compare the acute effects of two different types of resistance exercise (isometric versus isotonic) on exercise induced hypoalgesia during an aggravating activity, in participants with patellar tendinopathy.

Exercise is a commonly prescribed treatment for patients with musculoskeletal pain, and is effective in treating tendon pain. It is well documented, that an acute bout of aerobic or resistance type exercise reduces sensitivity to pain in healthy individuals. Therefore the efficacy of exercise as an intervention may be partially due to the analgesic effect of exercise, also termed exercise-induced hypoalgesia (EIH).

For tendinopathies, high load resistance exercise is frequently used during rehabilitation.

However, the optimal mode and dosages required for reducing pain in patients with tendinopathies is unknown. Understanding the effect of different forms of exercise on pain may help optimize the prescription of exercise for pain management.

A recent study by Rio and colleagues documented the acute effect of two different forms of resistance exercise in patients with patellar tendinopathy. The study compared, isometric resistance exercise (static muscular contractions), in comparison to isotonic resistance exercise (dynamic contractions) and found that isometric exercise induced greater participantive pain relief in response to an aggravating task. This study was the first to compare the analgesic effect of different forms of resistance exercise in patients with tendinopathy.

Although the results appear promising, a limitation of the study was that it did not quantify the effect of the different exercises on measures of pain sensitivity as in previous studies examining EIH.

Purpose The purpose of this study is to compare the acute effects of two different types of resistance exercise (isometric versus isotonic) on exercise induced hypoalgesia during an aggravating activity, in participants with patellar tendinopathy.

Hypothesis The primary hypothesis is that isometric exercise will induce greater pain relief/reduction during an aggravating activity in comparison to isotonic exercises.

Study Design and Methods The proposed study is a participant blinded, randomised crossover superiority trial, to examine acute effect of isometric versus isotonic resistance exercise on pain in patients with patellar tendinopathy. The trial will be pre-registered on clinicaltrials.gov before inclusion of participants commences.

Eligibility Criteria:
Inclusion Criteria:

* Men and women aged 18-40 years, with patellar tendinopathy will be included. Diagnosis of patellar tendinopathy, will be made by a physiotherapist (who has been trained by an experienced rheumatologist) as follows, similar to previously outlined criteria:

  * pain localised to the inferior pole of the patella during jumping and landing activities
  * pain during testing on the single-leg decline squat (SLDS)
  * The diagnosis will be confirmed by the presence of characteristic features on ultrasound imaging (eg, hypoechoic area and focal enlarged tendon).
  * Minimum pain of 3cm on a 10cm visual analogue scale (VAS)
  * Other concurrent diagnosable knee pathologies

Exclusion Criteria:

* Previous surgery of the knee
* Pregnancy
* Corticosteroid injection within the previous 6 months