If you don't remember your password, you can reset it by entering your email address and clicking the Reset Password button. You will then receive an email that contains a secure link for resetting your password
If the address matches a valid account an email will be sent to __email__ with instructions for resetting your password
Can we really say getting stronger makes your tendon feel better? No current evidence of a relationship between change in Achilles tendinopathy pain or disability and changes in Triceps Surae structure or function when completing rehabilitation: A systematic review
School of Health Sciences and Physiotherapy, The University of Notre Dame Australia, AustraliaNutrition and Health Innovation Research Institute, School of Medical and Health Sciences, Edith Cowan University, AustraliaSportsMed Subiaco, St John of God Healthcare, Australia
School of Health Sciences and Physiotherapy, The University of Notre Dame Australia, AustraliaSchool of Physiotherapy and Exercise Science, Curtin University, Australia
Nutrition and Health Innovation Research Institute, School of Medical and Health Sciences, Edith Cowan University, AustraliaInstitute for Health Research, The University of Notre Dame Australia, Australia
Monash Department of Clinical Epidemiology, Cabrini Institute, AustraliaSchool of Public Health and Preventative Medicine, Monash University, AustraliaLa Trobe Sport and Exercise Medicine Research Centre, La Trobe University, Australia
La Trobe Sport and Exercise Medicine Research Centre, La Trobe University, AustraliaDepartment of Family Practice, Faculty of Medicine, University of British Columbia, Vancouver, Canada
Determine if improvements in pain and disability in patients with mid-portion Achilles tendinopathy relate to changes in muscle structure and function whilst completing exercise rehabilitation.
Design
A systematic review exploring the relationship between changes in pain/disability and muscle structure/function over time, following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines.
Methods
Six online databases and the grey literature were searched from database inception to 16th December 2022 whereas clinical trial registries were searched from database inception to 11th February 2020. We included clinical studies where participants received exercise rehabilitation (±placebo interventions) for mid-portion Achilles tendinopathy if pain/disability and Triceps Surae structure/function were measured. We calculated Cohen's d (95 % confidence intervals) for changes in muscle structure/function over time for individual studies. Data were not pooled due to heterogeneity. Study quality was assessed using a modified Newcastle–Ottawa Scale.
Results
Seventeen studies were included for synthesis. No studies reported the relationship between muscle structure/function and pain/disability changes. Twelve studies reported muscle structure/function outcome measures at baseline and at least one follow-up time-point. Three studies reported improvements in force output after treatment; eight studies demonstrated no change in structure or function; one study did not provide a variation measure, precluding within group change over time calculation. All studies were low quality.
Conclusions
No studies explored the relationship between changes in tendon pain and disability and changes in muscle structure and function. It is unclear whether current exercise-based rehabilitation protocols for mid-portion Achilles tendinopathy improve muscle structure or function.
It is unclear whether current exercise rehabilitation protocols in Achilles tendinopathy improve muscle structure and/or function.
•
Caution should be taken if advising patients that exercise rehabilitation for Achilles tendinopathy is effective by virtue of improvements in muscle structure or function.
•
There was a lack of data available from completed trials, and a potential influence of measurement error on our results leading to a lack on confidence in any data reported by included studies.
1. Introduction
Loading protocols are considered standard care for managing Achilles tendinopathy and involve targeted exercise rehabilitation of the Triceps Surae to improve structure and function.
The rate of improvement of pain and function in mid-portion Achilles tendinopathy with loading protocols: a systematic review and longitudinal meta-analysis.
Different loading protocols exist for treating the symptoms and improving function in this condition (e.g. heavy eccentric calf training or heavy slow resistance training).
No programme appears superior to others for improvements in pain and disability, and the mechanisms underpinning the efficacy of these interventions remain unknown.
Improvement in pain and/or disability when completing loading protocols in the presence of tendinopathy may be related to improvements in muscle structure and function
However, the role of strength as a moderator to pain and disability for common musculoskeletal conditions, such as hip and knee osteoarthritis is lacking.
Moderators of the effects of therapeutic exercise for people with knee and hip osteoarthritis: a systematic review of sub-group analyses from randomised controlled trials.
Furthermore, interventions that have minimal impact on muscle structure and function (e.g. shock wave therapy or shoe heel raise inserts) are as effective for pain and disability as loading protocols in Achilles tendinopathy,
suggesting other mechanisms may improve symptoms. Improvement of symptoms has been observed within four weeks of commencing a loading programme (likely before muscle structure adapts
The rate of improvement of pain and function in mid-portion Achilles tendinopathy with loading protocols: a systematic review and longitudinal meta-analysis.
), which supports a hypothesis that other mechanisms contribute to clinical improvements in pain and disability.
Improvements in Triceps Surae structure and function may act as a stress shield to the Achilles tendon and contribute to improvements in symptoms of mid-portion Achilles tendinopathy.
Contributors to the overall function of the Triceps Surae include muscle structure, strength, endurance and power production (elements that can be measured in different ways).
Evaluating the progress of mid-portion Achilles tendinopathy during rehabilitation. A review of outcome measures for muscle structure and function, tendon structure and neural and pain associated mechanisms.
Muscle structure is a measure of the size and architecture of the Triceps Surae and can positively relate to force production through absolute cross-sectional area
Strength is a measure of maximal force output, endurance is a measure of the capacity to perform repeated tasks at a submaximal level for a large number of repetitions and power production is the ability to produce force rapidly.
Evaluating the progress of mid-portion Achilles tendinopathy during rehabilitation. A review of outcome measures for muscle structure and function, tendon structure and neural and pain associated mechanisms.
We wanted to answer the simple clinical query of whether changes in muscle structure/function relate to changes in Achilles tendon pain/disability whilst performing exercise rehabilitation, which we aimed to investigate with two research questions:
1.
Are improvements in Triceps Surae muscle structure and function associated with an improvement in mid-portion Achilles tendinopathy pain and/or disability?
2.
How effective are rehabilitation protocols for improving Triceps Surae structure and function in people with mid-portion Achilles tendinopathy (in the context of changes in pain and/or disability)?
2. Methods
Reporting of this systematic review exploring the relationship between changes in pain/disability and muscle structure/function over time was guided by the PRISMA recommendations.
The review protocol was prospectively registered (PROSPERO registration number: CRD42020149970) with existing literature, and relevant PROSPERO registrations screened to ensure no existing review had been conducted, or was being conducted.
We included studies of humans aged 18 years and over, who had a diagnosis of mid-portion Achilles tendinopathy. Mid-portion tendinopathy affects the body of the tendon approximately 2–7 cm proximal to the insertion (depending on the length of an individual's Achilles tendon) whereas insertional tendinopathy occurs near the tendon insertion onto the calcaneus.
Studies that did not state whether the included population was mid-portion or insertional were included. Studies where the population was mixed (i.e. mid-portion and insertional Achilles tendinopathy) were included if the majority of participants had mid-portion Achilles tendinopathy. We contacted authors and requested the data from participants with mid-portion Achilles tendinopathy. Studies that predominantly included insertional tendinopathy (e.g. insertional only) were excluded. Studies that included participants with other causes of heel pain were excluded.
Intervention studies using loading protocols were included. If the loading protocol intervention was combined with additional intervention(s) (e.g. laser or education), we excluded the treatment arm that received the additional intervention. If the loading protocol was combined with a sham intervention (e.g. sham laser), we included the treatment arm that received the sham intervention.
We included studies with self-reported measures of pain with loading, pain over a specified time-frame and disability.
ICON 2019—International Scientific Tendinopathy Symposium Consensus: there are nine core health-related domains for tendinopathy (CORE DOMAINS): Delphi study of healthcare professionals and patients.
ICON 2020—International Scientific Tendinopathy Symposium Consensus: a systematic review of outcome measures reported in clinical trials of Achilles tendinopathy.
Therefore, measures that only assessed pain without function or over time were excluded. For example, studies that only reported pain with palpation measured on a visual analogue scale were excluded.
Muscle structure was defined as the size and architectural properties of the Triceps Surae and any outcome measures that could assess this were included. Muscle function was broadly categorised as including strength, endurance, power production and/or plyometric capacity so any outcome measures assessing these elements were included.
Randomised and non-randomised intervention studies, cohort studies and case series were included if (i) at least one study arm used a loading protocol to treat mid-portion Achilles tendinopathy, and (ii) measured pain (with loading or pain over a specified timeframe) or disability, and (iii) any outcome measure of muscle structure or function was assessed at baseline and follow-up. Only the eligible arm(s) of multi-arm trials were included and subsequently treated as an individual cohort study for the purposes of this systematic review. Studies were included regardless of their publication status, provided they were complete and had data available. Reviews were excluded. We translated one study to English for screening and no other studies required translation.
Search strategies using free text terms (Appendix A) were implemented within electronic databases (PubMed, OVID (Medline), CINAHL (EBSCO), Cochrane Library, Web of Science and SPORTDiscus) from inception to 16th December 2022. We searched electronic databases of the grey literature (Proquest and OpenGrey) and clinical trial registries (Australia and New Zealand clinical trial registry, clinicaltrials.gov and the World Health Organization International Clinical Trials Registry Platform) from inception to 11 February 2020. Reference lists of reviews and retrieved articles were checked for additional studies missed in the electronic database search. The ePublication lists of key journals in the field (i.e., journals with included studies) were screened to identify studies yet to be indexed.
Records were exported to reference management software, EndNote 20, and Covidence. Duplicates were removed. Two review authors (MM and MT) independently screened the titles and abstracts of potentially eligible records. If it was unclear from the title and abstract whether an article met the inclusion criteria, the full text was obtained and screened. Disagreements were resolved by consensus or a third review author (WG) if consensus could not be reached. Studies were not anonymised prior to assessment.
Corresponding authors of study protocols, trial registrations or conference abstracts were contacted to determine if the study was completed, and subsequently request access to the final dataset/publication. Corresponding authors were also contacted in the event two studies appeared similar, to determine if the publications represented a single trial.
Two review authors (MM and MT) independently assessed study quality for each study using a modified version (Appendix B) of the Newcastle–Ottawa Scale. Each domain of the scale was judged as low quality, unclear quality or high quality.
The scale was modified given no tool exists for assessing study quality in correlation studies. We pilot tested our modified Newcastle–Ottawa scale prior to using it in the systematic review. Disagreements were resolved by consensus or a third review author (WG) if consensus could not be reached.
The overall quality judgement for each study was assigned based on the lowest study quality criterion from all domains. Studies were classified as unclear for attrition bias if they did not state how many people had completed the assessment of muscle structure and function at all time points. To be high quality due to measurement error, studies had to determine reliability of the muscle structure and function outcome measures for the participants with mid-portion Achilles tendinopathy, and use either a validated tool or the gold standard assessment tool. We assessed study quality for comparative studies by treating each arm of a randomised trial as a separate cohort.
Studies with sample sizes fewer than 50 were considered at high risk of small study bias, studies with samples between 50 and 200 were considered at moderate risk of small study bias and studies with sample sizes greater than 200 were considered at low risk of small study bias.
Do sideline tests of vestibular and oculomotor function accurately diagnose sports-related concussion in adults? A systematic review and meta-analysis.
We considered the influence of small study biases and methodological quality on the outcomes reported by included studies. Studies at high risk of small study bias and of low quality were considered unlikely to represent a true within group change over time, whereas studies with low risk of small study bias and high quality were considered to likely represent a true within group change over time.
Two review authors (MM and MT) independently extracted data from all included studies using Microsoft Excel. Discrepancies were resolved by consensus. The following data items were extracted: primary author, year of publication, study design (including study affiliation, funding information and study sponsor), study population (diagnosis, diagnostic criteria and whether imaging was used), sample size (including sample size at baseline and final follow-up point), baseline demographics (mean (SD) age, height, weight, BMI, gender and duration of pain), loading intervention, 12 items of the TIDieR checklist,
follow-up time points for both short-term (<4 weeks) and longer-term (>4 weeks) follow-ups and mean, standard deviation, sample size and statistical relationship (correlation and/or crude or adjusted odds/risk ratios) between the change in pain and/or disability and the change in the measure of muscle structure or function from baseline to follow-up within four weeks of the intervention (short-term follow-up) and baseline to all follow-up points whilst completing the intervention > four weeks (long-term follow-up).
Where the mean (SD) for measures of muscle structure and function was not available the corresponding author was contacted to provide these data.
As no study provided the data necessary for a meta-analysis of correlation, no synthesis was possible for Objective One. Due to substantial differences in the loading protocols performed, and the methods used to assess muscle structure and function, the data for longitudinal changes in muscle structure and function (Objective Two) were not pooled and are instead described using a qualitative synthesis.
Demographic data for all studies were presented as count, mean and standard deviation (or the non-parametric equivalent). The results of the individual studies are presented with muscle structure and function outcomes grouped under the assessment type (e.g. isometric versus isokinetic dynamometry). The magnitude of change from baseline is provided by ‘Cohen's d’ and 95 % confidence intervals (95 % CI) for the within group change for muscle structure and function were also calculated using https://www.psychometrica.de/effect_size.html. The data used from this review are available via the full-text of included studies excluding the study by Van der Vlist which was provided upon request and not publicly available.
We planned a meta-analysis of correlation using the Hunter–Schmidt method in R to determine the population effect ().
However, due to an absence of appropriate data, meta-analysis was precluded. We planned to evaluate statistical heterogeneity using I2 with substantial statistical heterogeneity being classified as P < 0.10.
Additionally, we planned to assess funnel plots for each correlation of interest. Assessment of heterogeneity and funnel plots were not undertaken due to the lack of meta-analysis and small numbers of studies (<10 studies per outcome domain) for each outcome domain.
To account for bias, we planned sensitivity analyses of studies that used a combined loading protocol and sham intervention
Effect of high-volume injection, platelet-rich plasma, and sham treatment in chronic midportion Achilles tendinopathy: a randomized double-blinded prospective study.
Effect of a 12-week eccentric and isometric training in Achilles tendinopathy on the gastrocnemius muscle: an ultrasound shear wave elastography study.
However, given the absence of appropriate data, we were unable to conduct this.
3. Results
4538 records were identified, and 36 records, representing 29 trials, met the selection criteria (Fig. 1, Appendix C). Appendix C summarises how duplicate studies and trial registries were managed.
Effect of high-volume injection, platelet-rich plasma, and sham treatment in chronic midportion Achilles tendinopathy: a randomized double-blinded prospective study.
Effect of a 12-week eccentric and isometric training in Achilles tendinopathy on the gastrocnemius muscle: an ultrasound shear wave elastography study.
Demographic information is provided in Table 1. All studies provided some measure of muscle structure and function. Three studies performed isometric dynamometry of ankle plantarflexion force output.
Effect of high-volume injection, platelet-rich plasma, and sham treatment in chronic midportion Achilles tendinopathy: a randomized double-blinded prospective study.
The effect of combined Action Observation Therapy with eccentric exercises in the treatment of mid-portion Achilles-tendinopathy: a feasibility pilot randomised controlled trial.
Effect of a 12-week eccentric and isometric training in Achilles tendinopathy on the gastrocnemius muscle: an ultrasound shear wave elastography study.
All 17 studies reported that clinical diagnosis was used to establish participants had mid-portion Achilles tendinopathy. However, the reporting quality of diagnostic criteria varied.
Effect of high-volume injection, platelet-rich plasma, and sham treatment in chronic midportion Achilles tendinopathy: a randomized double-blinded prospective study.
Effect of a 12-week eccentric and isometric training in Achilles tendinopathy on the gastrocnemius muscle: an ultrasound shear wave elastography study.
The effect of combined Action Observation Therapy with eccentric exercises in the treatment of mid-portion Achilles-tendinopathy: a feasibility pilot randomised controlled trial.
Studies had large amounts of missing data relating to the reporting of descriptive data for baseline and follow-up outcomes for muscle structure and function. Nine studies did not report outcomes at all follow-up periods.
Effect of high-volume injection, platelet-rich plasma, and sham treatment in chronic midportion Achilles tendinopathy: a randomized double-blinded prospective study.
Effect of a 12-week eccentric and isometric training in Achilles tendinopathy on the gastrocnemius muscle: an ultrasound shear wave elastography study.
Effect of high-volume injection, platelet-rich plasma, and sham treatment in chronic midportion Achilles tendinopathy: a randomized double-blinded prospective study.
Effect of a 12-week eccentric and isometric training in Achilles tendinopathy on the gastrocnemius muscle: an ultrasound shear wave elastography study.
Across the 17 trials, representing 25 cohorts, there were 432 participants with a mean (SD) age ranging from 20.1 (1.8) to 55 (6.5) years. Twenty-two of the cohorts reported the proportion of females included, which varied from 0 % to 86 % with seven cohorts not including any females.
Effect of high-volume injection, platelet-rich plasma, and sham treatment in chronic midportion Achilles tendinopathy: a randomized double-blinded prospective study.
Effect of high-volume injection, platelet-rich plasma, and sham treatment in chronic midportion Achilles tendinopathy: a randomized double-blinded prospective study.
Effect of a 12-week eccentric and isometric training in Achilles tendinopathy on the gastrocnemius muscle: an ultrasound shear wave elastography study.
The effect of combined Action Observation Therapy with eccentric exercises in the treatment of mid-portion Achilles-tendinopathy: a feasibility pilot randomised controlled trial.
Effect of high-volume injection, platelet-rich plasma, and sham treatment in chronic midportion Achilles tendinopathy: a randomized double-blinded prospective study.
Effect of a 12-week eccentric and isometric training in Achilles tendinopathy on the gastrocnemius muscle: an ultrasound shear wave elastography study.
The effect of combined Action Observation Therapy with eccentric exercises in the treatment of mid-portion Achilles-tendinopathy: a feasibility pilot randomised controlled trial.
No studies analysed correlations or controlled for major confounders. One study adjusted the primary analysis (i.e. age, sex, BMI and duration of symptoms).
Effect of high-volume injection, platelet-rich plasma, and sham treatment in chronic midportion Achilles tendinopathy: a randomized double-blinded prospective study.
Effect of a 12-week eccentric and isometric training in Achilles tendinopathy on the gastrocnemius muscle: an ultrasound shear wave elastography study.
The effect of combined Action Observation Therapy with eccentric exercises in the treatment of mid-portion Achilles-tendinopathy: a feasibility pilot randomised controlled trial.
No studies reported the relationship between changes in pain and disability and changes in muscle structure and function when completing exercise rehabilitation.
Effect of high-volume injection, platelet-rich plasma, and sham treatment in chronic midportion Achilles tendinopathy: a randomized double-blinded prospective study.
Effect of a 12-week eccentric and isometric training in Achilles tendinopathy on the gastrocnemius muscle: an ultrasound shear wave elastography study.
The effect of combined Action Observation Therapy with eccentric exercises in the treatment of mid-portion Achilles-tendinopathy: a feasibility pilot randomised controlled trial.
Effect of high-volume injection, platelet-rich plasma, and sham treatment in chronic midportion Achilles tendinopathy: a randomized double-blinded prospective study.
Effect of a 12-week eccentric and isometric training in Achilles tendinopathy on the gastrocnemius muscle: an ultrasound shear wave elastography study.
The effect of combined Action Observation Therapy with eccentric exercises in the treatment of mid-portion Achilles-tendinopathy: a feasibility pilot randomised controlled trial.
Effect of a 12-week eccentric and isometric training in Achilles tendinopathy on the gastrocnemius muscle: an ultrasound shear wave elastography study.
Neither study had significant within group change over time (Appendix G). However, based on small sample sizes, and low-quality studies it is currently unclear whether current rehabilitation protocols result in changes to ankle plantar flexor muscle structure.
Three studies (n = 51), representing six cohorts, investigated isometric ankle plantar flexion joint torque (Appendix H).
One of the six cohorts had significant within group change over time (Appendix G). However, based on small sample sizes, and low-quality studies it is currently unclear whether current rehabilitation protocols result in changes to isometric ankle plantar flexion joint torque.
Six studies, representing eight cohorts, investigated plantar flexion joint torque using isokinetic dynamometry at varied speeds and assessment procedures (Appendix I).
following rehabilitation (Appendix G). However, based on small sample sizes, and low-quality studies it is currently unclear whether current rehabilitation protocols result in changes to isokinetic ankle plantar flexion joint torque.
Six studies, representing eight cohorts, investigated performance of the heel raise capacity (Table 2).
Effect of high-volume injection, platelet-rich plasma, and sham treatment in chronic midportion Achilles tendinopathy: a randomized double-blinded prospective study.
The effect of combined Action Observation Therapy with eccentric exercises in the treatment of mid-portion Achilles-tendinopathy: a feasibility pilot randomised controlled trial.
Effect of high-volume injection, platelet-rich plasma, and sham treatment in chronic midportion Achilles tendinopathy: a randomized double-blinded prospective study.
The effect of combined Action Observation Therapy with eccentric exercises in the treatment of mid-portion Achilles-tendinopathy: a feasibility pilot randomised controlled trial.
One cohort (n = 12), had significant improvements in the left leg only at 12 weeks, with no improvements, in any leg demonstrated at the six-week follow-up in either cohort.
The effect of combined Action Observation Therapy with eccentric exercises in the treatment of mid-portion Achilles-tendinopathy: a feasibility pilot randomised controlled trial.
None of the remaining three studies with data (n = 135) had significant within group change over time within the affected limb (Appendix G). However, based on small sample sizes, and low-quality studies it is currently unclear whether current rehabilitation protocols result in changes to heel raise capacity.
Table 2Intervention outcomes on heel raise capacity.
Effect of high-volume injection, platelet-rich plasma, and sham treatment in chronic midportion Achilles tendinopathy: a randomized double-blinded prospective study.
The effect of combined Action Observation Therapy with eccentric exercises in the treatment of mid-portion Achilles-tendinopathy: a feasibility pilot randomised controlled trial.
Legend: SD = standard deviation, n = number, J = joules, not reported = these data were collected but not reported within the study, not assessed = these data were not assessed. Bold = 95% confidence intervals do not cross zero.
(Appendix G). However, based on small sample sizes, and low-quality studies it is currently unclear whether current rehabilitation protocols result in changes to plyometric performance.
4. Discussion
Loading protocols are prescribed for mid-portion Achilles tendinopathy as standard care.
The rate of improvement of pain and function in mid-portion Achilles tendinopathy with loading protocols: a systematic review and longitudinal meta-analysis.
One rationale for prescribing loading protocols is to improve the structure and function of the Triceps Surae muscle, thus shielding the Achilles tendon and improve symptoms via modulation of aggravating loads.
Due to the small number of studies, sample size, quality of reporting and low overall quality of included studies, it is not possible to conclude whether loading protocols do or do not impact muscle structure and function as the results presented within this study are unlikely to represent the true within group change over time.
Only four of twenty-five cohorts reported a significant change in within-group effect sizes over time, with one of those studies including uninjured limbs
The effect of combined Action Observation Therapy with eccentric exercises in the treatment of mid-portion Achilles-tendinopathy: a feasibility pilot randomised controlled trial.
The effect of combined Action Observation Therapy with eccentric exercises in the treatment of mid-portion Achilles-tendinopathy: a feasibility pilot randomised controlled trial.
and may explain some of these differences in results.
The results of this systematic review are unable to support a strong relationship between improvements in muscle structure/function and tendon pain/disability given no studies have currently investigated this outcome. This outcome was surprising given the clinical dogma that muscular adaptation is, in part, responsible for clinical improvements in pain and/or disability within tendinopathy patients.
Our results challenge current thinking related to the mechanisms underpinning improvements in patients with tendinopathy who are completing rehabilitation and highlight the need of future research to explore this relationship.
Furthermore, this review has highlighted the lack of conclusive evidence that current rehabilitation protocols are effective at changing participants muscle structure and function over time.
Increased force output through the local muscle (e.g. Triceps Surae) may more effectively modulate load through the tendon and improve symptoms.
The poor study quality and small numbers of included studies notwithstanding, the lack of force output gains we observed might explain why a large proportion of patients continue to experience symptoms following rehabilitation.
The rate of improvement of pain and function in mid-portion Achilles tendinopathy with loading protocols: a systematic review and longitudinal meta-analysis.
One of the reasons for the apparent lack of improvement of muscle structure and function with these loading protocols may be the differences in these protocols to accepted resistance training protocols.
as other eccentric exercises would be expected to alter muscle structure (in healthy participants) when designed according to accepted resistance training guidelines.
The eccentric protocol is a one-size-fits-all approach, does not conform to suggested repetition or volume quantum, does not conform to suggested training frequency and provides no information on rest durations or time under tension. This lack of comparability is not surprising given the eccentric protocol was published over ten years prior to the American College of Sports Medicine position statement on resistance training.
The lack of definitive results may be that the majority of cohorts with data used an eccentric protocol (64 %) and weighted the results. However, the only study to report consistent positive results on muscle force output used an eccentric protocol
Alternatively, the lack of change to muscle structure and function may be due to abnormal cortical inhibition, which has been demonstrated in patellar tendinopathy
but has yet to be investigated within Achilles tendinopathy.
An alternative explanation for the apparent lack of improvement in muscle structure and function is that outcome measures inaccurately quantified force output. Only two cohorts were high quality in relation to measurement error
which diminishes confidence in any conclusions drawn. However, the studies with low risk of measurement error used the eccentric protocol and did not demonstrate any significant improvement in plantar flexion force output.
Other biopsychosocial mechanisms are likely associated with improvements in clinical symptoms following exercise rehabilitation. Differences in tendon structure between people with Achilles tendinopathy and controls are present in cross-sectional studies
However, changes in tendon structure over time with rehabilitation are inconsistent and the relationship of these changes to tendon symptoms is unclear.
In most loading trials, improvements in tendon-related disability happen in a timeframe that is unlikely to be driven by changes in muscle structure (i.e. <4 weeks).
The rate of improvement of pain and function in mid-portion Achilles tendinopathy with loading protocols: a systematic review and longitudinal meta-analysis.
Do people with unilateral mid-portion Achilles tendinopathy who participant in running-related physical activity exhibit a meaningful conditioned pain modulation (CPM) effect: a pilot study.
Patellar and Achilles tendinopathies are predominantly peripheral pain states: a blinded case control study of somatosensory and psychological profiles.
Changes in these features whilst completing a loading protocol may indicate clinical improvement, even when muscle structure and function remain unchanged. Therefore, interventions that are designed to target not only muscle structure and function, but also central and peripheral processing deficits, may represent an appropriate treatment target for rehabilitation protocols.
We performed a detailed search of published and grey literature to reduce the chance of publication bias. However, whilst we were able to identify numerous relevant trials (n = 29) the main limitation of this review was the lack of data available from completed trials (n = 17) and the potential influence of measurement error.
5. Conclusion
It is unclear whether current rehabilitation protocols for mid-portion Achilles tendinopathy improved muscle structure and/or function when completing rehabilitation. No studies analysed the relationship between changes in pain and disability and changes in muscle structure and function with rehabilitation. All studies reported improvements in pain/disability, however only three of seventeen trials demonstrated improvement in muscle function with rehabilitation. All studies were low quality.
Funding information
This research did not receive any specific grant from funding agencies in the public, commercial or not-for-profit sector.
Confirmation of ethical compliance
Not applicable.
CRediT authorship contribution statement
MM, MT and WG conceived the review. MM, MT, WG and CA designed the protocol. MM performed all searches. MM and MT performed all screening, extraction, and risk of bias assessment. MM and PC performed all analysis. All authors contributed to interpretation of results and manuscript preparation.
Declaration of interest statement
MM, MT, JD and SD have received speaker fees for lectures on tendinopathy. ER has received speaker fees for lectures on tendinopathy and has designed an app for anterior knee pain rehabilitation. PC and WG declare that they have no conflict of interest. CA is the Editor-in-Chief at Journal of Orthopaedic & Sports Physical Therapy.
Acknowledgements
MM is supported by an Australian Government Research Training Program Fee Offset Scholarship through the Australian National Health and Medical Research Council. ER is supported by an Early Career Fellowship from the Australian National Health and Medical Research Council. CA has received research salary support for work in return to sport from the Australian National Health and Medical Research Council, Swedish Research Council, and Swedish Research Council for Sport Science.
The rate of improvement of pain and function in mid-portion Achilles tendinopathy with loading protocols: a systematic review and longitudinal meta-analysis.
Moderators of the effects of therapeutic exercise for people with knee and hip osteoarthritis: a systematic review of sub-group analyses from randomised controlled trials.
Evaluating the progress of mid-portion Achilles tendinopathy during rehabilitation. A review of outcome measures for muscle structure and function, tendon structure and neural and pain associated mechanisms.
ICON 2019—International Scientific Tendinopathy Symposium Consensus: there are nine core health-related domains for tendinopathy (CORE DOMAINS): Delphi study of healthcare professionals and patients.
ICON 2020—International Scientific Tendinopathy Symposium Consensus: a systematic review of outcome measures reported in clinical trials of Achilles tendinopathy.
Do sideline tests of vestibular and oculomotor function accurately diagnose sports-related concussion in adults? A systematic review and meta-analysis.
Effect of high-volume injection, platelet-rich plasma, and sham treatment in chronic midportion Achilles tendinopathy: a randomized double-blinded prospective study.
Effect of a 12-week eccentric and isometric training in Achilles tendinopathy on the gastrocnemius muscle: an ultrasound shear wave elastography study.
The effect of combined Action Observation Therapy with eccentric exercises in the treatment of mid-portion Achilles-tendinopathy: a feasibility pilot randomised controlled trial.
Do people with unilateral mid-portion Achilles tendinopathy who participant in running-related physical activity exhibit a meaningful conditioned pain modulation (CPM) effect: a pilot study.
Patellar and Achilles tendinopathies are predominantly peripheral pain states: a blinded case control study of somatosensory and psychological profiles.
00045-2&id=gr1.jpg){kind=link}