Effect of resistance exercise dose components for tendinopathy management: a systematic review with meta-analysis

Key Points

1. Exercise therapy is the main mode of conservative treatment for tendinopathies with a focus on resistance exercise, which is shown to be effective in improving patient outcomes.
2. Resistance exercise dose is poorly reported within tendinopathy management literature.
3. This meta-analysis identified some consistent patterns indicating greater efficacy on average with therapies prescribing higher intensities (through inclusion of additional loads) and lower frequencies.

BACKGROUND & OBJECTIVE

Tendinopathy is a prevalent condition involving degenerative changes within tendons of both children and adults (1). It affects athletic and non-athletic populations and can manifest in persistent pain, swelling, loss of function and diminished movement (2-5). Exercise therapy is the mainstay of conservative management and has focused largely on resistance exercise, often eccentric actions, to encourage load tolerance leading to structural adaptations at the musculotendinous unit and functional restoration (5-7). Its effectiveness is likely to be influenced not only by the specific exercises but also the magnitude of the stimulus, quantified by the concept of exercise dose.

The aim of this study was to investigate potential moderating effects of resistance exercise dose components, including intensity, volume, and frequency, through contemporary meta-analysis and meta-regression approaches in order to explore the heterogeneity and assess for general trends regarding dose-response relationships.

Exercise therapy is the mainstay of conservative management and has focused largely on resistance exercise.

Greater loads and greater volumes of load likely lead to more robust biological signaling for adaptation to the imposed demands.

METHODS

The authors’ search strategy identified a total of 12,379 potential studies, with 6,944 remaining following de-duplication. After title and abstract screening, 440 studies were retained for full-text screening. Of these studies, a further 330 were excluded based primarily on insufficient description of the exercise stimulus (141 studies) and not including exercise-only treatment arms (79 studies). In total, data from 110 studies comprising 148 treatment arms and 3953 participants were included in the meta-analyses.

The intervention being assessed was exercise therapy where resistance exercise represented the dominant class. Intervention arms combining exercise with other non-exercise therapies were not included. Included in the study were studies in which resistance exercise was delivered in a range of settings by a range of health and exercise professionals or support workers, as well as supervised or unsupervised (including home) exercise.

Attempts were made to code exercise dose components (intensity, volume and frequency) for each study; however, sufficient information was not always available to code all three components.

The authors included outcomes that assessed six domains:

1. Disability

2. Function

3. Pain (e.g. pain on loading, pain over a specified time, pain without further specification)

4. Range of motion

5. Physical function capacity

6. Quality of life

RESULTS

Despite the extensive variability in therapies, some general patterns were identified in the data. These findings indicated that increased loading with greater time for recovery may produce superior results. Meta-regressions consistently identified greater effect size estimates for therapies employing higher intensity exercise through the addition of external loads compared with body mass only. Similarly, meta-regressions consistently identified greater effect size estimates for therapies performed with a low frequency (less than once per day) compared with very high frequencies (once per day or more than once per day) that were also likely to comprise reduced loading to enable recovery.

One of the challenges in investigating resistance intensity was the lack of clear reporting of intensities used. Studies using resistance bands did not report the relative resistance provided or in general comment on intensity progression. Although some studies identified progression in intensity through additional loading using, for example, a dumbbell or loaded backpack, many did not state the actual loads recommended or used. Evidence from the review indicating superior results with greater resistance training intensities is consistent with findings from previous studies that have also reported better adaptive responses in the mechanical properties of tendons.

LIMITATIONS

One of the limitations of this study, and a challenge for future evidence syntheses, is the lack of clear reporting. The authors found that in general, exercise volume and frequency were better reported, with reporting of intensity often poor. Similarly, the review identified that although load progression was frequently stated, studies rarely reported the actual loads or intensity used.

Another limitation to note is that the extracted resistance dose data was for the primary exercise, therefore, other exercises prescribed as part of the wider intervention were not accounted for in the analysis. This means that variables such as exercise volume may not be fully representative of the true volume of overall exercise performed, but rather specifically the dominant resistance exercise.

CLINICAL IMPLICATIONS

The results of this study provide evidence suggesting that where resistance exercise is being prescribed for tendinopathy management, clinicians should consider whether a sufficient stimulus with regards to exercise intensity is being adopted and whether there is appropriate time for recovery. For certain patients, this may require a period of progression before reaching higher intensities that the patient can tolerate without increases in pain that delay future bouts of loading.

When appropriate, clinicians should consider prescribing higher intensities of resistance exercise through the application of external loads rather than just body mass; and given the increased loading, prescribing lower frequencies of sessions (less than daily) to allow for adequate recovery. Taken in the context of foundational biological loading principles such as Wolff’s and Davis’ Laws, emphasis being placed on achieving a stimulus strong enough to induce physiologic and structural adaptation to the target tissue has both face validity and biological plausibility.

Greater loads and greater volumes of load likely lead to more robust biological signaling for adaptation to the imposed demands. Further refinement of the interrelations between exercise dose parameters and patient characteristics is required, including better understanding of the influence of exercise volume.

+STUDY REFERENCE

Pavlova A, Shim J, Moss R, Maclean R, Brandie D, Mitchell L, Greig L, Parkinson E, Alexander L, Brown V, Morrissey D, Cooper K, Swinton P (2023) Effect of resistance exercise dose components for tendinopathy management: a systematic review with meta-analysis. Br J Sports Med. Published online ahead of print.

SUPPORTING REFERENCE

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4. Scott A, Squier K, Alfredson H, et al. Icon 2019: international scientific tendinopathy symposium consensus: clinical terminology. Br J Sports Med 2020;54:260–2.
5. Alfredson H. The chronic painful Achilles and Patellar tendon: research on basic biology and treatment. Scand J Med Sci Sports 2005;15:252–9.
6. O’Neill S, Watson PJ, Barry S. Why are eccentric exercises effective for Achilles tendinopathy? Int J Sports Phys Ther 2015;10:552–62.
7. Young JL, Rhon DI, Cleland JA, et al. The influence of exercise dosing on outcomes in patients with knee disorders: a systematic review. J Orthop Sports Phys Ther 2018;48:146–61.