Resistance Training Interventions for Lower Limb Tendinopathies: A Scoping Review of Resistance Training Reporting Content, Quality, and Scientific Implementation

The objectives of this scoping review were as follows: (1) to describe what exercises and intervention variables are used in resistance training interventions for lower limb tendinopathy,  (2) to assess the completeness of reporting as assessed by the Consensus on Exercise Reporting Template (CERT) and the Toigo and Boutellier framework, and (3) to assess the implementation of scientific resistance training principles. We searched MEDLINE, CINAHL, AMED, Embase, SPORTDiscus, and Cochrane Library databases. Randomized controlled trials, cohort studies, case series, case reports, and observational studies that reported using resistance exercises for lower limb tendinopathies were considered for inclusion, with 194 studies meeting the inclusion criteria. Completeness of the reporting of exercise descriptors and programme variables was assessed by the CERT and the Toigo and Boutellier framework. Reporting of exercise descriptor items from the Toigo and Boutellier framework ranged from 0 to 13, with an average score of 9/13, with only 9 studies achieving a full 13/13. Reporting of items from the CERT ranged from 0 to 18, with an average score of 13/19. No study achieved a full 19/19; however, 8 achieved 18/19. Scoring for resistance training principles ranged from 1 to 10, with only 14 studies achieving 10/10. Eccentric heel-drops were the most common exercise (75 studies), followed by isotonic heel raises (38), and single-leg eccentric decline squats (27). The reporting of exercise descriptors and intervention content was high across studies, with most allowing exercise replication, particularly for Achilles and patellar tendinopathy. However, reporting for some tendinopathies and content items such as adherence was poor, limiting optimal translation to clinical practice.


Introduction
Tendinopathy represents a spectrum of potential changes to healthy tendons, leading to tendon damage and disease, with changes characterised by abnormal tendon composition and cellularity, ultimately leading to altered tendon microstructure [1].In tendinopathic tendons, the normal arrangement of collagen fibres and organisation of tenocytes become altered by mechanical overuse, which leads to tendinopathy symptoms of pain, inflammation, swelling, and impaired physical function and performance [2].Despite all healthy tendons having the capability to progress to tendinopathy, tendons of the lower limb may have an increased risk for mechanical overload which causes tendon changes, such as disruption to the normal collagen matrix structure [3].Although the aetiology of tendinopathy has yet to be fully elucidated, it is considered the result of a disrupted tendon healing process, with the hallmarks of collagen derangement, neovascularisation, altered tendon structure, and tissue calcification [4].Tendinopathies account for up to 30% of all sports-related injuries with a range of extrinsic and intrinsic risk factors identified, suggesting that each individual pathogenesis of tendinopathy is multifactorial [5,6].e higher prevalence of patellar and Achilles tendinopathy found in athletes may be related to repetitive tendon microtrauma from repeated athletic movements such as running, jumping, and landing [7].Prevalence of Achilles and patellar tendinopathy have been reported to be as high as 23% and 45% in runners and jumping athletes, respectively.Plantar heel pain was reported to be found in up to 18% of running athletes in one cohort [8][9][10].
Despite a recent proliferation in clinical research investigating effectiveness of a range of treatment options for tendinopathy, it remains unclear which treatments are most effective, with exercise-based treatments such as resistance training currently being the most recommended due to consistent findings of efficacy [11,12].Common adjunctive treatments to exercise in clinical practice, which have conflicting findings of effectiveness include shockwave therapy, ultrasound, low-level laser therapy, manual therapy, and corticosteroid injections [13].Isolated eccentric resistance training and heavy slow resistance training involving isotonic contractions have been shown to have favourable outcomes for common lower limb tendinopathies including Achilles tendinopathy, patellar tendinopathy, and plantar heel pain [14][15][16][17].e high loads encountered during resistance training may stimulate tendon healing by counteracting structural tendon alteration, leading to reorganization and remodelling of collagen fibres, therefore improving the mechanical properties of tendons [18].Despite positive outcomes, a limitation of some resistance training interventions in tendinopathy studies is that description, prescription, and progression of exercises and program variables may be poorly defined and reported, making translation to clinical practice difficult [19].If the exercise dosage and training parameters prescribed clinically is insufficient, then, the mechanobiological stimulus may not be adequate to initiate tendon healing and positive outcomes from the intervention [20].Despite the optimal dosage of resistance training for tendinopathy being unknown [21], research has shown an association between positive outcomes and higher exercise dosages in other musculoskeletal disorders [22].
In recent years, several guidelines or frameworks have been developed for reporting exercise interventions and specific exercise details within research studies in order to enhance reproducibility of exercise interventions and their translation to clinical practice [23].e need to standardise reporting of components of exercise interventions has been highlighted by the development of the Consensus on Exercise Reporting Template (CERT), which advocates reporting detailed descriptions of exercises and their variables such as progression and tailoring, to allow clinical replication [24].However, a limitation of the CERT is its omission of mechanobiological resistance training descriptors such as those included in the Toigo and Boutellier framework, such as rest intervals, time under tension, and relative load [25].Holden et al. [26] recently highlighted how the poor reporting of exercise interventions in patellofemoral pain limits the clinical translation of exercise research findings in this population, with the authors recommending that future studies should use both the CERT and Toigo and Boutellier framework in conjunction as they report different aspects of exercise prescription and would therefore be complementary.It is unclear if a similar issue exists within the interventional exercise literature in lower limb tendinopathies as no previous reviews have been conducted investigating the reporting of exercise descriptors using recommended frameworks.Although reporting of exercise interventions using the CERT has been recommended in tendinopathy to improve transparency and clinical translation, it is unclear if this recommendation has been widely adopted in research studies [27][28][29].Both the CERT and Toigo and Boutellier framework are recommended templates and have been used in several review studies evaluating exercise descriptions and variables in rehabilitation for musculoskeletal disorders other than tendinopathy [30][31][32].
Although there has been a proliferation of clinical research examining resistance training treatment interventions for lower limb tendinopathies in recent years, it is unclear if these interventions have been sufficiently reported to allow clinical replication.erefore, conducting a comprehensive scoping review of the current literature is warranted to investigate this question [29].A search of MEDLINE, CINAHL, Cochrane Library, and PEDro identified no reviews with the objective of evaluating the reporting of resistance exercises and variables within interventions for lower limb tendinopathies using recommended frameworks such as the CERT or Toigo and Boutellier framework [33].
erefore, the aims of this scoping review were to evaluate the reporting of exercise

Methods
Due to the exploratory nature of the research questions of this review, a scoping review was conducted as they are recommended for mapping key concepts, evidence gaps, and types of evidence within a particular field [34].Scoping reviews can help guide future research and the possibility of conducting systematic reviews on the topic.As the aim of this review was to evaluate reporting across all study designs implementing resistance training for lower limb tendinopathies, rather than evaluate effectiveness, a scoping review was more appropriate than a systematic review.is scoping review was conducted in accordance with the Joanna Briggs Institute (JBI) methodology for scoping reviews [34].e scoping review was reported in accordance with the Preferred Reporting Items for Systematic reviews and Meta-Analysis extension for Scoping Reviews (PRISMA-ScR) [34].
e findings allowed for dissemination of the parameters of research exercise interventions to clinical practitioners,

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Translational Sports Medicine allowing increased likelihood of implementation in clinical practice [26].e review also outlined future research and exercise reporting needs within lower limb tendinopathy resistance training interventions.

Study Identification.
e inclusion criteria for this scoping review were guided by a modified PICO, which includes population, concept, and context (PCoCo), as recommended for scoping reviews [34].e review included adults aged eighteen years or older with a diagnosis of a lower limb tendinopathy for any time duration.All lower limb tendinopathies were included, such as gluteal, hamstring, patellar, Achilles, tibialis posterior, and peroneal tendinopathy.Plantar heel pain was included as it is considered to have a similar pathophysiology to tendinopathy and should therefore be treated in accordance with other lower limb tendinopathies according to recent literature [19].e concept of interest was resistance training for the treatment of lower limb tendinopathies, including any type or format of resistance training.e resistance training may be used as a first-or second-line intervention and may be delivered in isolation or combined with other treatments.Resistance training may be delivered across any healthcare or exercise setting, delivered by health or exercise professionals, in a supervised or unsupervised manner, using any methods for training progression and monitoring. is scoping review considered both experimental and quasiexperimental study designs including randomized controlled trials and nonrandomized controlled trials.In addition, prospective and retrospective cohort studies, case series, and case reports were considered for inclusion.Unpublished studies, reviews, or reports were not considered.

Search Strategy.
A 3-step search strategy was implemented in this scoping review.It incorporated the following: (1) A limited search of MEDLINE and CINAHL using initial keywords, followed by analysis of the text words in the title or abstract and those used to describe articles to develop a full search strategy.(2) e full-search strategy was adapted to each database and applied to MEDLINE, CINAHL, AMED, Embase, SPORTDiscus, Cochrane Library (controlled trials and systematic reviews), and PEDro.e following trial registries were searched: ClinicalTrials.gov,ISRCTN, e Research Registry, EU-CTR (European Union Clinical Trials Registry), and ANZCTR (Australia and New Zealand Clinical Trials Registry).Databases were searched from inception to December 31, 2021.Although Stanish and Curwin [35] first published on the concept of eccentric resistance training for tendinopathy in 1986, it was only following the publication of the Alfredson protocol in 1998 [36] that resistance training became widespread in lower limb tendinopathy rehabilitation.Despite this, databases were searched from inception to ensure key articles and seminal studies on the topic published before 1998 were not omitted, which may influence overall findings.(3) For each article located in steps 1 and 2, a search of cited and citing articles using Scopus and hand-searching, where necessary, was conducted.Studies published in a language other than English were only included if a translation was available as translation services were not available to the authors.

Study Selection.
Following the search, all identified citations were collated and uploaded into RefWorks, with duplicates being removed.Titles and abstracts were then screened by two independent reviewers (IB and AM) for assessment against the inclusion criteria for the review.Potentially relevant studies were retrieved in full, and their citation details imported into Covidence (Veritas Health Innovation, Melbourne, Australia).Two independent reviewers (IB and AM) then assessed the full text of selected citations in detail against the inclusion criteria.Any disagreements that arose between the reviewers at each stage of the study selection process were resolved through discussion or by input from a third reviewer.e results of the search were reported in accordance with the PRISMA-ScR (Figure 1) [34].
2.4.Data Extraction.Data were extracted from sources included in the scoping review by one reviewer, with independent data extraction by a second reviewer for 10% of studies.e data were extracted using an excel spreadsheet developed specifically by the reviewers for each source type.
e data extracted included specific details regarding the population, concept, context, study methods, and key findings relevant to the review questions.Any disagreements that arose between the reviewers were resolved through discussion.e data extracted included dimensions such as authors, year of publication, study type, purpose, population and sample size, methods, details of resistance training intervention, specific exercises, and outcome measures used.Details of the resistance training interventions included setting, mode of delivery, type, dosage, and methods used to progress and adjust the training stimulus.e contents and variables of the specific resistance training exercises were extracted using the 13-item Toigo and Boutellier framework for exercise mechanobiological determinants and included parameters such as repetitions, load magnitude, and time under tension.General information from the resistance training interventions such as exercise supervision and delivery methods were extracted using the CERT tool.An evaluation of the implementation of scientific resistance training principles was also conducted, by extracting data on the principles of specificity, overload, progression, individualisation, and adherence.e definitions and scoring criteria for these principles are provided in Tables 1 and 2. In accordance with guidance on conducting scoping reviews, critical appraisal was not conducted [34].

Data Analysis.
e extracted data were analysed using descriptive statistics, with findings presented in tabular form as tables and figures, in a manner that aligns with the objective of this scoping review.A narrative summary accompanies the tabulated results and describes how the results relate to the review objective and questions.
e number of items that described the Toigo and Boutellier framework exercise descriptors ranged from 0 to 13 out of a possible 13, with an average score across the 194 studies of 9/13.Only 9 [19,50,79,155,175,177,201,217,221] (5%) studies achieved a full 13/13 for reporting items from the framework, with three of these from the same author [19,217,221].Overall reporting across all studies for each item is reported in Figure 2.Only 3 items were reported by less than 80% of studies, rest between sets 47 (24%), time under tension 34 (18%), and volitional muscular failure 15 (8%).e item with the highest percentage of reporting at 97% was the contraction mode of the exercise employed in the intervention, reported in 188 studies.Of the 19 items included in the CERT, reporting among included studies ranged from 0 to 18, with an average score of 13/19.No study achieved a full score of 19, but 8 [15,50,79,110,111,137,177,221] (4%) studies achieved a high score of 18/19.Four of these studies [50,79,177,221] also achieved a full score of 13/13 for reporting exercise descriptors.Overall reporting for each item is presented in Figure 3.Most items were well-reported across studies, with seven items being reported in less than 70% of studies, progression rules 133 (69%), tailored how 134 (69%), adherence measures 94 (49%), exercise delivered   Translational Sports Medicine  Translational Sports Medicine  Translational Sports Medicine as planned 70 (36%), adverse events 55 (28%), fidelity measured 11 (6%), and motivation strategies 4 (2%), with the latter two items particularly poorly reported across the studies.Previous studies assessing the completeness of CERT items in musculoskeletal rehabilitation determined that reporting completeness of items could be regarded as high (>75%), moderate (60 to 74%), or low (<60%) [225,226].Based on this classification, 10 items can be rated as high, 4 as moderate, and 5 as low.

Application of Resistance Training
Principles.An evaluation of the implementation of scientific resistance training principles was conducted by evaluating the design and reporting of the key principles of specificity, overload, progression, individualisation, and adherence (Table 1).One point each was given for the design and reporting of each of the 5 principles, with a maximum score of 10/10 available.e scoring system was based on scales used in previous reviews with the same objective [11,227,228]

Discussion
e main findings from this scoping review are that the description and reporting of resistance training exercises and intervention parameters used in the rehabilitation of lower limb tendinopathies were generally well reported across studies.However, some reporting areas of weakness were identified, with items such as adherence, fidelity, and specific exercise progression parameters of interventions, being poorly reported.A broad range of resistance training Translational Sports Medicine types were implemented with eccentric training the most common at 67%, with Alfredson eccentric heel-drops (39%), isotonic heel raises (20%), and eccentric decline single-leg squats (14%) being the most implemented exercises.Most studies included sufficient information on exercise dosage (load, repetitions, sets, and frequency) to allow replication of the exercises in both research and clinical settings.However, not all studies provided sufficient detail to allow replication, suggesting there is room for improvement in future research, with items such as adherence and fidelity of interventions being poorly reported.Whereas the scientific resistance training principles of specificity and overload were well implemented and reported throughout the studies, the principals of progression, individualisation, and adherence had poorer reporting, preventing complete clinical replication of these principles in some studies.Despite these issues, the overall moderate to high quality of reporting was better for lower limb tendinopathies than for other musculoskeletal conditions as assessed in other reviews applying the CERT.For example, the quality of exercise content reporting has been found to be considerably lower in exercise rehabilitation interventions for hamstring strains [225], groin injury [226], Achilles tendon ruptures [30], rotator cuff disorders [32], knee osteoarthritis [229,230], patellofemoral pain [26], knee injuries [31], fibromyalgia [231], juvenile arthritis [232], hand osteoarthritis [233], pelvic floor dysfunction [234,235], low back pain [236,237], ACL injury [238], and femoral-acetabular impingement [239].
e only other review reporting an overall moderate-high quality for CERT reporting like this review, was for hip osteoarthritis, which reported an average CERTscore of 13/19 [240].Item 8 of the CERT relates to describing exercises to a level that allows replication, which was met by 85% of studies included in this review.In comparison, reporting of this item was much lower in the reviews for hamstring strains [225] (43%), knee osteoarthritis [230] (26%), rotator cuff disorders [32] (29%), groin injuries [226] (15%), and Achilles tendon ruptures [30] (26%).
ese findings highlight the comparative quality of exercise reporting for lower limb tendinopathies.e reasons  12 Translational Sports Medicine for exercise reporting quality being higher for lower limb tendinopathies compared to other musculoskeletal conditions are unclear but could be related to the fact that resistance training has been considered the gold standard first-line intervention which has been recommended for many years [11].is review employed two common tools to describe resistance exercise implementation and reporting; the CERT which evaluates general information about the specific exercise intervention; and the Toigo and Boutellier framework which evaluates mechanobiological and exercise dosage descriptors, alongside an evaluation of five key scientific resistance training principles.e completeness of exercise reporting was high overall across the included studies, but the poor reporting of some items and key resistance training principles is concerning and limits the true translation of the findings regarding the resistance exercises to clinical practice.For example, the poor overall reporting on the specific loading employed during resistance exercise for progression, makes this principle difficult to replicate and translate to clinical practice.Although the Toigo and Boutellier framework is a well-accepted tool for reporting exercise descriptors in the literature, some of the items which were poorly reported in the included studies could theoretically be considered too detailed and impractical to properly implement both clinically and in research.
e items, rest between sets, time under tension, and volitional muscular failure were all poorly reported; however, it could be argued these items are the least relevant for exercise replication.Despite this, their inclusion would allow for a complete replication of the resistance training interventions implemented in the studies, which may be a more optimal scenario for prescribing resistance exercise to patients to ensure complete translation of the protocols.As a tool that was developed in the sports science literature, it is not rehabilitation specific, so key aspects of resistance exercises in the rehabilitation setting are not accounted for such as the patients psychological state, level of pain, and tolerance to exercise.Similarly, while most items on the CERT were well reported, several items were very poorly reported such as motivational strategies, fidelity measures, adherence, adverse events, and if exercises were delivered as planned.Although the absence of these items does not prevent exercise replication, their inclusion would optimise replication in the clinical setting.It is concerning that only 2% of studies reported using motivational strategies, which may impact on exercise adherence, and overall reporting of adherence was lacking, despite many studies stating they employed adherence tracking measures such as exercise diaries.e very poor reporting of fidelity and adherence highlighted in this review, highlights the need for future studies to focus on practical implementation issues to ensure translation to clinical practice.If fidelity and adherence of the interventions are not monitored and reported, then, the quality of the exercise intervention reported in studies may be of less value.While the combination of both scales would allow exercise replication in a clinical setting, in isolation, they would likely not be sufficient.erefore, the development of a more rehabilitation specific scale for implementing and reporting resistance training interventions should be explored in future research to optimise clinical translation of research resistance exercise interventions.
4.1.Clinical Implications.For many years, progressive resistance training has been considered the gold standard intervention for rehabilitating lower limb tendinopathies.Optimising rehabilitation outcomes for patients with lower limb tendinopathies requires implementing the most effective evidence-based resistance training interventions.However, interventions shown to be efficacious in high-quality research must also be replicable and translatable to the clinical setting.To achieve this, research interventions must follow scientific resistance training principles and include enough detail to be reproducible.Many of the studies included in this review which have shown good outcomes also score highly for replicability on the scales employed, particularly those using eccentric heel raises for Achilles tendinopathy and eccentric decline squats for patellar tendinopathy.ese protocols should remain the gold standard first-line intervention for clinicians as they have not only been found to be effective in the individual studies but can also be fully replicated clinically.e supplementary material for this review provides all the extracted data and key prescription content from the interventions and can help to guide clinicians in clinical practice.Several studies [50,79,177,221] scored highly across all the reporting tools employed, so the authors recommend these as a starting point for clinicians requiring fully reproducible resistance training programs for implementing in rehabilitation for lower limb tendinopathies.

Implications for Research.
In comparison to reviews on other musculoskeletal pathologies in physical therapy, which have evaluated exercise reporting, this review has found that reporting of resistance exercise for lower limb tendinopathies is generally of high quality, despite shortcomings in areas such as adherence reporting.is is in stark contrast to reviews on other common musculoskeletal disorders where the reporting was considered poor overall.Indeed, the average scores found in this review for the CERT and Toigo and Boutellier framework are higher than for all the other pathologies previously listed.However, this review has highlighted potential weaknesses in the delivery of exercise, with poor reporting of adherence, fidelity, exercise motivational strategies, and specific progression parameters.e implementation of these items should be addressed in future research to optimise clinical translation and outcomes for resistance training interventions in lower limb tendinopathies.Until a rehabilitation specific exercise reporting scale is validated, and available, future studies should continue to design and implement resistance training protocols using scales such as the CERT and Toigo and Boutellier framework, to ensure they are clinically reproducible.
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Strengths and Limitations.
is scoping review has included a broad range of study designs from RCTs to individual case reports, with a broad range of interventions, so there is therefore vast heterogeneity in findings across all the studies, so findings should be interpreted with caution.However, determining effectiveness of interventions through meta-analysis techniques was not the objective of the review, with the aims focused on the description, reporting, and implementation of resistance training in interventions for lower limb tendinopathies.Only studies available in English language were included, which may introduce language bias.To provide a comprehensive analysis and state of the art review on reporting of resistance training interventions for lower limb tendinopathies, all primary study designs were considered.Despite all primary designs being included, this review did not consider review papers or clinical practice guidelines, which may have included detailed exercise reporting.Databases were searched from inception, and there was no limitation on sample size or intervention duration.Although many studies included were published before the publication of the CERT (2016) and Toigo and Boutellier framework (2006), there was no obvious reporting discrepancies from earlier to more recent studies, despite the culture of reporting becoming more widespread in recent years [23,26].Both scales are transparent and contain sufficient exercise details to allow 100% replication if fully followed, despite not being rehabilitation or tendinopathy specific.Most of the studies included in this review were for Achilles and patellar tendinopathies which also had the highest quality reporting, with other lower limb tendinopathies poorly represented and with comparatively poorer overall reporting quality.
erefore, the findings of this review cannot be generalised to all lower limb tendinopathies, with future research required to address the dearth of resistance training interventions for non-Achilles and patellar lower limb tendinopathies.

Conclusion
Resistance training interventions and specific exercises are generally well reported across all primary study designs for treating lower limb tendinopathies, particularly eccentric training for Achilles and patellar tendinopathy.However, certain reporting items and training principles related to the delivery of exercise were poorly reported and implemented, including adherence, fidelity, exercise motivational strategies, and specific progression parameters.While most studies provided sufficient details to allow clinical exercise replication, the weaknesses highlighted must be addressed in future research to allow resistance training interventions and exercises to be fully clinically reproducible to enhance rehabilitation outcomes.
descriptors and programme variables used within resistance training interventions for treating lower limb tendinopathies.e scoping review was guided by addressing the following review questions on specific aspects of exercise reporting within lower limb tendinopathy resistance training interventions: (1) What exercises and program variables are used in resistance training interventions for lower limb tendinopathy?(2) How complete is the reporting of the exercise descriptors and programme variables as assessed by the CERT and the Toigo and Boutellier framework?(3) Do studies implement scientific resistance training principles?

Figure 2 :
Figure 2: Percentage of studies (out of 194) with complete reporting for each item of the Toigo and Boutellier framework.
IF EXERCISES DELIVERED AS PLANNED 16A.DESCRIBE HOW EXERCISE FIDELITY MEASURED 15.DESCRIBE STARTING LEVEL 14B.DESCRIBE HOW TAILORING WAS DONE 14A.DESCRIBE IF GENERIC OR TAILORED

Table 1 :
Resistance training principles and training intervention criteria assessed.
RepetitionsHow many repetitions of each exercise or target number of repetitions Exercise selection Outline and description of specific exercises used in intervention Adherence Was adherence to the training intervention monitored and reported?4 Translational Sports Medicine Completeness of information regarding the resistance training interventions is presented as the number of complete items of the CERT, Toigo and Boutellier framework, and resistance training principles for each study.Resistance training exercises were categorised as eccentric, concentric, isometric, isotonic, heavy slow resistance training (HSRT), low-load blood flow restricted training (BFRT), isoinertial, manually resisted, hip strength, and general strength exercise.

Table 2 :
Application and reporting of key training principles.

Table 3 :
Characteristics and reporting scores of the 194 included studies.