Fibril morphology and tendon mechanical properties in patellar tendinopathy: effects of heavy slow resistance training

From Tissue to System: What Constitutes an Appropriate Response to Loading?

Optimal loading involves the prescription of an exercise stimulus that promotes positive tissue adaptation, restoring function in patients undergoing rehabilitation and improving performance in healthy athletes. Implicit in optimal loading is the need to monitor the response to load, but what constitutes a normal response to loading? And does it differ among tissues (e.g., muscle, tendon, bone, cartilage) and systems? In this paper, we discuss the "normal" tissue response to loading schema and demonstrate the complex interaction among training intensity, volume, and frequency, as well as the impact of these training variables on the recovery of specific tissues and systems. Although the response to training stress follows a predictable time course, the recovery of individual tissues to training load (defined herein as the readiness to receive a similar training stimulus without deleterious local and/or systemic effects) varies markedly, with as little as 30 min (e.g., cartilage reformation after walking and running) or 72 h or longer (e.g., eccentric exercise-induced muscle damage) required between loading sessions of similar magnitude. Hyperhydrated and reactive tendons that have undergone high stretch-shorten cycle activity benefit from a 48-h refractory period before receiving a similar training dose. In contrast, bone cells desensitize quickly to repetitive loading, with almost all mechanosensitivity lost after as few as 20 loading cycles. To optimize loading, an additional dose (≤ 60 loading cycles) of bone-centric exercise (e.g., plyometrics) can be performed following a 4-8 h refractory period. Low-stress (i.e., predominantly aerobic) activity can be repeated following a short (≤ 24 h) refractory period, while greater recovery is needed (≥ 72 h) between repeated doses of high stress (i.e., predominantly anaerobic) activity. The response of specific tissues and systems to training load is complex; at any time, it is possible that practitioners may be optimally loading one tissue or system while suboptimally loading another. The consideration of recovery timeframes of different tissues and systems allows practitioners to determine the "normal" response to load. Importantly, we encourage practitioners to interpret training within an athlete monitoring framework that considers external and internal load, athlete-reported responses, and objective markers, to contextualize load-response data.

Advancements in Therapeutic Approaches for Degenerative Tendinopathy: Evaluating Efficacy and Challenges

Degenerative tendinopathy results from the accumulation of minor injuries following unsuccessful tendon repair during acute tendon injuries. The process of tendon repair is prolonged and varies between individuals, making it susceptible to reinjury. Moreover, treating chronic tendinopathy often requires expensive and extensive rehabilitation, along with a variety of combined therapies to facilitate recovery. This condition significantly affects the quality of life of affected individuals, underscoring the urgent need for more efficient and cost-effective treatment options. Although traditional treatments have improved significantly and are being used as substitutes for surgical interventions, the findings have been inconsistent and conflicting. This review aims to clarify these issues by exploring the strengths and limitations of current treatments as well as recent innovations in managing various forms of degenerative tendinopathy.

Comprehensive assessment of heavy slow resistance training and high-dose therapeutic ultrasound in managing patellar tendinopathy, a randomized single-blind controlled trial

BACKGROUND

Patellar tendinopathy (PT) is a common sport injury prone to recurrence. Heavy Slow Resistance Training (HSR) and High-Dose Therapeutic Ultrasound (TUS) are frequently used interventions for PT. However, the combined effectiveness of these therapies remains unclear. This study investigated the impact of combination therapy on functional outcomes in patients with PT.

METHODS

Fifty-one college students aged 18-25, diagnosed with PT via musculoskeletal ultrasound, were randomly assigned to one of three groups (n = 17 per group): combined HSR and high-dose TUS, HSR training alone, or high-dose TUS alone. The eight-week intervention included assessments using the Victorian Institute of Sport Assessment-Patella (VISA-P), Visual Analogue Scale (VAS), Y-balance Test (YBT), Modified Thomas Test (MTT), Horizontal Jumping Distance, Maximum Isometric Muscle Strength Test, and musculoskeletal ultrasound for patellar tendon thickness and blood flow. Assessments were conducted at baseline and post-intervention, with a follow-up VISA-P assessment at week 16. This randomized, single-blind controlled trial was registered on ISRCTN11447397 ( www.ISRCTN.com ) on February 17, 2024 (retrospectively registered).

RESULTS

All groups demonstrated significant improvements in VISA-P scores at the end of the intervention compared to baseline (p < 0.01), with the combined group showing the greatest improvement (21 points). Follow-up at week 16 revealed continued improvement in VISA-P scores for the combined and HSR groups, while the TUS group showed a slight decrease (from 74 to 70). All groups displayed significantly reduced VAS scores post-intervention (p < 0.01) compared to baseline, indicating decreased pain. While no significant between-group differences were observed in pre-intervention VAS scores, post-intervention results revealed significant differences between the combined and HSR groups (p < 0.05), as well as between the combined and TUS groups (p < 0.01).

CONCLUSION

Both exercise intervention and high-dose TUS appear effective in reducing pain and improving motor function in individuals with PT. However, the therapeutic effect of high-dose TUS alone seems limited compared to exercise intervention. The combined application of both methods yielded the most significant improvements in pain relief and motor function enhancement.

Topical glyceryl trinitrate (GTN) and eccentric exercises in the treatment of mid-portion achilles tendinopathy (the NEAT trial): a randomised double-blind placebo-controlled trial

OBJECTIVES

To investigate if daily treatment with glyceryl trinitrate (GTN) ointment, over 24 weeks combined with a 12-week eccentric exercise programme is more effective for chronic mid-portion Achilles tendinopathy than placebo ointment and eccentric exercise.

METHODS

This was a single-site randomised double-blind placebo-controlled trial at an acute hospital, Dublin, Ireland. Patients with chronic mid-portion Achilles tendinopathy were randomised to either 24 weeks of daily GTN ointment or placebo ointment. Both groups received an identical 12-week eccentric exercise programme. The primary outcome measure was the Victorian Institute of Sport Assessment-Achilles (VISA-A) questionnaire at 24 weeks, which measures pain, function and activity. Secondary outcomes included pain severity, self-reported physical function, calf muscle function, pressure pain thresholds and ultrasound changes. Statistical analyses were performed according to intention-to-treat principles.

RESULTS

76 patients (30 women; 46 men, mean age±SD, 45.6±8.2 years) were recruited for the trial. Significant improvements in VISA-A scores occurred in both groups at 6-week, 12-week and 24-week follow-up. The increase was not significantly different between groups, adjusted mean between-group difference from baseline to week 6, -1.33 (95% CI -6.96 to 4.31); week 12, -1.25 (95% CI -8.0 to 5.49) and week 24, -3.8 (95% CI -10.6 to 3.0); negative values favour GTN. There was no significant between-group difference in any of the secondary outcome measures at 6, 12 and 24 weeks.

CONCLUSIONS

Adding daily GTN ointment over 24 weeks to a 12-week eccentric exercise programme did not improve pain, function and activity level in patients with chronic mid-portion Achilles tendinopathy when compared with placebo ointment.

Do therapeutic exercises impact supraspinatus tendon thickness? Secondary analyses of the combined dataset from two randomized controlled trials in patients with rotator cuff-related shoulder pain

BACKGROUND

The mechanistic response of rotator cuff tendons to exercises within the context of rotator cuff-related shoulder pain (RCRSP) remains a significant gap in current research. A greater understanding of this response can shed light on why individuals exhibit varying responses to exercise interventions. It can also provide information on the influence of certain types of exercise on tendons. The primary aim of this article is to explore if changes in supraspinatus tendon thickness (SSTT) ratio differ between exercise interventions (high load vs. low load). The secondary aims are to explore if changes in SSTT ratio differ between ultrasonographic tendinopathy subgroups (reactive vs. degenerative) and if there are associations between tendinopathy subgroups, changes in tendon thickness ratio, and clinical outcomes (disability).

METHODS

This study comprises secondary analyses of the combined dataset from two randomized controlled trials that compared high and low-load exercises in patients with RCRSP. In those trials, different exercise interventions were compared: 1) progressive high-load strengthening exercises and 2) low-load strengthening with or without motor control exercises. In 1 trial, there was also a third group that was not allocated to exercises (education only). Ultrasound-assessed SSTT ratio, derived from comparing symptomatic and asymptomatic sides, served as the primary measure in categorizing participants into tendinopathy subgroups (reactive, normal and degenerative) at baseline.

RESULTS

Data from 159 participants were analyzed. Two-way repeated measures ANOVAs revealed significant Group (P < .001) and Group × Time interaction (P < .001) effects for the SSTT ratio in different tendinopathy subgroups, but no Time effect (P = .63). Following the interventions, SSTT ratio increased in the "Degenerative" subgroup (0.14 [95% confidence interval {CI}: 0.09-0.19]), decreased in the "Reactive" subgroup (-0.11 [95% CI: -0.16 to -0.06]), and remained unchanged in the "Normal" subgroup (-0.01 [95% CI: -0.04 to 0.02]). There was no Time (P = .21), Group (P = .61), or Group × Time interaction (P = .66) effect for the SSTT ratio based on intervention allocation. Results of the linear regression did not highlight any significant association between the tendinopathy subgroup (P = .25) or change in SSTT ratio (P = .40) and change in disability score.

CONCLUSION

Findings from this study suggest that, over time, SSTT in individuals with RCRSP tends to normalize, compared to the contralateral side, regardless of the exercise intervention. Different subgroups of symptomatic tendons behave differently, emphasizing the need to potentially consider tendinopathy subtypes in RCRSP research. Future adequately powered studies should investigate how those different tendinopathy subgroups may predict long-term clinical outcomes.

Neural network auto-segmentation of serial-block-face scanning electron microscopy images exhibit collagen fibril structural differences with tendon type and health

A U-Net machine learning algorithm was adapted to automatically segment tendon collagen fibril cross-sections from serial block face scanning electron microscopy (SBF-SEM) and create three-dimensional (3D) renderings. We compared the performance of routine Otsu thresholding and U-Net for a positional tendon that has low fibril density (rat tail tendon), an energy-storing tendon that has high fibril density (rat plantaris tendon), and a high fibril density tendon hypothesized to have disorganized 3D ultrastructure (degenerated rat plantaris tendon). The area segmentation of the tail and healthy plantaris tendon had excellent accuracy for both the Otsu and U-Net, with an Intersection over Union (IoU) of 0.8. With degeneration, only the U-Net could accurately segment the area, whereas Otsu IoU was only 0.45. For boundary validation, the U-Net outperformed Otsu segmentation for all tendons. The fibril diameter from U-Net was within 10% of the manual segmentation, however, the Otsu underestimated the fibril diameter by 39% in healthy plantaris and by 84% in the degenerated plantaris. Fibril geometry was averaged across the entire image stack and compared across tendon types. The tail had a lower fibril area fraction (58%) and larger fibril diameter (0.31 µm) than the healthy plantaris (67% and 0.21 µm) and degenerated plantaris tendon (66% and 0.19 µm). This method can be applied to a large variety of tissues to quantify 3D collagen fibril structure.

Exercise entrainment of musculoskeletal connective tissue clocks

The musculoskeletal system, crucial for movement and support, relies on the delicate balance of connective tissue homeostasis. Maintaining this equilibrium is essential for tissue health and function. There has been increasing evidence in the past decade that shows the circadian clock as a master regulator of extracellular matrix (ECM) homeostasis in several connective tissue clocks. Very recently, exercise has emerged as a significant entrainment factor for cartilage and intervertebral disk circadian rhythms. Understanding the implications of exercise on connective tissue peripheral clocks holds promise for enhancing tissue health and disease prevention. Exercise-induced factors such as heat, glucocorticoid release, mechanical loading, and inter-tissue cross talk may play pivotal roles in entraining the circadian rhythm of connective tissues. This mini review underscores the importance of elucidating the mechanisms through which exercise influences circadian rhythms in connective tissues to optimize ECM homeostasis. Leveraging exercise as a modulator of circadian rhythms in connective tissues may offer novel therapeutic approaches to physical training for preventing musculoskeletal disorders and enhancing recovery.

Effects of low-load blood flow restriction training in healthy adult tendons: A systematic review and meta-analysis

OBJECTIVE

To systematically review the effects of low-load blood flow restriction training (LL-BFR) on healthy adult tendons.

DESIGN

A systematic review with meta-analysis.

LITERATURE SEARCH

Six electronic databases were searched by two researchers.

STUDY SELECTION CRITERIA

Clinical trials comparing the effects of LL-BFR to high-load resistance training (HL-RT) or low-load resistance training (LL-RT) in healthy adult tendons.

DATA SYNTHESIS

Two reviewers selected the eligible clinical trials, and one reviewer exported the data. Two reviewers evaluated the study quality and risk of bias using the PEDro scale and the ROB2 scale. We performed meta-analysis where appropriate using a random-effects model. We rated the quality of evidence using GRADE.

RESULTS

Six studies were eligible. We analyzed tendon cross-sectional area (CSA) and tendon stiffness as the outcomes. Across all comparisons, there was low-to moderate-quality evidence of a difference between LL-BFR and LL-RT immediately after exercise. There was high-quality evidence of no difference between LL-BFR and HL-RT in the long term.

CONCLUSION

The effects of LL-BFR on the tendons depends on the time and dose of the intervention. LL-BFR could be useful to increase the CSA of the tendons in a similar or superior way to HL-RT after 8 weeks of intervention.

Maximal Lower Limb Strength in Patellar Tendinopathy: A Systematic Review With Meta-Analysis

OBJECTIVE

To investigate whether lower limb strength is reduced in people with patellar tendinopathy (PT) compared with asymptomatic control individuals or the asymptomatic contralateral limb.

DATA SOURCES

MEDLINE, PubMed, Scopus, and Web of Science.

STUDY SELECTION

To be included in the systematic review and meta-analysis, studies were required to be peer reviewed, published in the English language, and case control investigations; include participants with a clinical diagnosis of PT and an asymptomatic control or contralateral limb group; and include an objective measure of lower limb maximal strength.

DATA EXTRACTION

We extracted descriptive statistics for maximal strength for the symptomatic and asymptomatic limbs of individuals with PT and the limb(s) of the asymptomatic control group, inferential statistics for between-groups differences, participant characteristics, and details of the strength-testing protocol. The risk of bias was assessed using the Joanna Briggs Institute critical appraisal tool for analytical cross-sectional studies.

DATA SYNTHESIS

Of the 23 included studies, 21 reported knee strength, 3 reported hip strength, and 1 reported ankle strength. Random-effects models (Hedges g) were used to calculate the pooled effect sizes (ESs) of muscle strength according to the direction of joint movement and type of contraction. The pooled ESs (95% CI) for maximal voluntary isometric contraction knee-extension strength, concentric knee-extension strength, and concentric knee-flexion strength were 0.54 (0.27, 0.80), 0.78 (0.30, 1.33), and 0.41 (0.04, 0.78), respectively, with all favoring greater strength in the asymptomatic control group. Researchers of 2 studies described maximal eccentric knee-extensor strength with no differences between the PT and asymptomatic control groups. In 3 studies, researchers measured maximal hip strength (abduction, extension, and external rotation), and all within-study ESs favored greater strength in the asymptomatic control group.

CONCLUSIONS

Isometric and concentric knee-extensor strength are reduced in people with PT compared with asymptomatic control individuals. In contrast, evidence for reduced eccentric knee-extension strength in people with PT compared with asymptomatic control individuals is limited and inconsistent. Although evidence is emerging that both knee-flexion and hip strength may be reduced in people with PT, more examination is needed to confirm this observation.

Exercise therapy for tendinopathy: a mixed-methods evidence synthesis exploring feasibility, acceptability and effectiveness

Background

Tendinopathy is a common, painful and functionally limiting condition, primarily managed conservatively using exercise therapy.

Review questions

(i) What exercise interventions have been reported in the literature for which tendinopathies? (ii) What outcomes have been reported in studies investigating exercise interventions for tendinopathy? (iii) Which exercise interventions are most effective across all tendinopathies? (iv) Does type/location of tendinopathy or other specific covariates affect which are the most effective exercise therapies? (v) How feasible and acceptable are exercise interventions for tendinopathies?

Methods

A scoping review mapped exercise interventions for tendinopathies and outcomes reported to date (questions i and ii). Thereafter, two contingent systematic review workstreams were conducted. The first investigated a large number of studies and was split into three efficacy reviews that quantified and compared efficacy across different interventions (question iii), and investigated the influence of a range of potential moderators (question iv). The second was a convergent segregated mixed-method review (question v). Searches for studies published from 1998 were conducted in library databases (n = 9), trial registries (n = 6), grey literature databases (n = 5) and Google Scholar. Scoping review searches were completed on 28 April 2020 with efficacy and mixed-method search updates conducted on 19 January 2021 and 29 March 2021.

Results

Scoping review - 555 included studies identified a range of exercise interventions and outcomes across a range of tendinopathies, most commonly Achilles, patellar, lateral elbow and rotator cuff-related shoulder pain. Strengthening exercise was most common, with flexibility exercise used primarily in the upper limb. Disability was the most common outcome measured in Achilles, patellar and rotator cuff-related shoulder pain; physical function capacity was most common in lateral elbow tendinopathy. Efficacy reviews - 204 studies provided evidence that exercise therapy is safe and beneficial, and that patients are generally satisfied with treatment outcome and perceive the improvement to be substantial. In the context of generally low and very low-quality evidence, results identified that: (1) the shoulder may benefit more from flexibility (effect sizeResistance:Flexibility = 0.18 [95% CrI 0.07 to 0.29]) and proprioception (effect sizeResistance:Proprioception = 0.16 [95% CrI -1.8 to 0.32]); (2) when performing strengthening exercise it may be most beneficial to combine concentric and eccentric modes (effect sizeEccentricOnly:Concentric+Eccentric = 0.48 [95% CrI -0.13 to 1.1]; and (3) exercise may be most beneficial when combined with another conservative modality (e.g. injection or electro-therapy increasing effect size by ≈0.1 to 0.3). Mixed-method review - 94 studies (11 qualitative) provided evidence that exercise interventions for tendinopathy can largely be considered feasible and acceptable, and that several important factors should be considered when prescribing exercise for tendinopathy, including an awareness of potential barriers to and facilitators of engaging with exercise, patients' and providers' prior experience and beliefs, and the importance of patient education, self-management and the patient-healthcare professional relationship.

Limitations

Despite a large body of literature on exercise for tendinopathy, there are methodological and reporting limitations that influenced the recommendations that could be made.

Conclusion

The findings provide some support for the use of exercise combined with another conservative modality; flexibility and proprioception exercise for the shoulder; and a combination of eccentric and concentric strengthening exercise across tendinopathies. However, the findings must be interpreted within the context of the quality of the available evidence.

Future work

There is an urgent need for high-quality efficacy, effectiveness, cost-effectiveness and qualitative research that is adequately reported, using common terminology, definitions and outcomes.

Study registration

This project is registered as DOI: 10.11124/JBIES-20-00175 (scoping review); PROSPERO CRD 42020168187 (efficacy reviews); https://osf.io/preprints/sportrxiv/y7sk6/ (efficacy review 1); https://osf.io/preprints/sportrxiv/eyxgk/ (efficacy review 2); https://osf.io/preprints/sportrxiv/mx5pv/ (efficacy review 3); PROSPERO CRD42020164641 (mixed-method review).

Funding

This project was funded by the National Institute for Health and Care Research (NIHR) HTA programme and will be published in full in HTA Journal; Vol. 27, No. 24. See the NIHR Journals Library website for further project information.

Gluteal Tendinopathy: Critical Analysis Review of Current Nonoperative Treatments

» Gluteal tendinopathy/greater trochanteric pain syndrome (GTPS) is the most prevalent of all lower limb tendinopathies, affecting 1 in 4 women older than 50 years and commonly individuals within their fifth and sixth decades of life regardless of activity level.» The condition is believed to originate from age-related degenerative changes about the hip abductor tendon insertions and the surrounding bursae, and is exacerbated by congenital and acquired abnormal hip biomechanics.» Treatment of gluteal tendinopathy/GTPS often begins with noninvasive nonoperative modalities such as activity modifications, nonsteroidal anti-inflammatory drugs, and physical therapy. For recalcitrant symptoms, additional nonoperative therapies have been used; however, there remains a lack of comparative efficacy between these adjunct treatments.» In this article, we examine the available literature regarding the nonoperative management of gluteal tendinopathy/GTPS and provide insight into the effectiveness of current treatment modalities.

Longitudinal Evidence for High-Level Patellar Tendon Strain as a Risk Factor for Tendinopathy in Adolescent Athletes

BACKGROUND

High tendon strain leads to sub-rupture fatigue damage and net-catabolic signaling upon repetitive loading. While high levels of tendon strain occur in adolescent athletes at risk for tendinopathy, a direct association has not yet been established. Therefore, in this prospective longitudinal study, we examined the hypothesis that adolescent athletes who develop patellar tendon pain have shown increased levels of strain in advance.

METHODS

In 44 adolescent athletes (12-17 years old), patellar tendon mechanical properties were measured using ultrasonography and inverse dynamics at four time points during a season. Fourteen athletes developed clinically relevant tendon pain (SYM; i.e., reduction of the VISA-P score of at least 13 points), while 23 remained asymptomatic (ASYM; VISA-P score of > 87 points). Seven cases did not fall into one of these categories and were excluded. Tendon mechanical properties of SYM in the session before the development of symptoms were compared to a randomly selected session in ASYM.

RESULTS

Tendon strain was significantly higher in SYM compared to ASYM (p = 0.03). The risk ratio for developing symptoms was 2.3-fold higher in athletes with tendon strain ≥9% (p = 0.026). While there was no clear evidence for systematic differences of the force applied to the tendon or tendon stiffness between SYM and ASYM (p > 0.05), subgroup analysis indicated that tendon force increased prior to the development of symptoms only in SYM (p = 0.034).

DISCUSSIO

The study provides novel longitudinal evidence that high tendon strain could be an important risk factor for patellar tendinopathy in adolescent athletes. We suggest that inadequate adaptation of tendon stiffness to increases in muscle strength may occur if adolescent athletes are subject to mechanical loading which does not  provide effective tendon stimulation.

A New Test for Achilles Tendinopathy Based on Kager's Fat Pad Clinical Assessment Predictive Values

Background This study aimed to check the diagnostic accuracy of a new test to identify Achilles tendinopathy.

STUDY DESIGN

Observational study.

METHODS

Seventy patients recruited from a private medical centre met the diagnostic criteria for unilateral Achilles tendinopathy (age, 45.1 ± 12.7 years; weight, 75.00 ± 10 kg; height, 1.75 ± 0.1 m) and were tested based on both Achilles tendons. Seventy patients with a unilateral Achilles tendinopathy ultrasound diagnosis were tested using David's test.

RESULTS

Most (86%) subjects demonstrated Kager's fat pad asymmetry in relation to the Achilles tendon in the complete passive dorsiflexion in the prone position (David's sign). No healthy tendons had David's sign.

CONCLUSIONS

The presence of asymmetry in Kager's fat pad in relation to the Achilles tendon during complete passive dorsiflexion is strongly indicative of ultrasound-diagnosed tendinopathy. David's test demonstrated a sensitivity of 85.71% (95% CI, 77.51% to 93.91%) and a specificity of 100% (95% CI, 100% to 100%), while noting the lack of blinding of the assessors and the uncertainty of the diagnostic measures (95% CI). Asymmetry of the fat pad could potentially serve as a characteristic marker for patients with Achilles tendinopathy.

Overload in a Rat In Vivo Model of Synergist Ablation Induces Tendon Multiscale Structural and Functional Degeneration

Tendon degeneration is typically described as an overuse injury with little distinction made between magnitude of load (overload) and number of cycles (overuse). Further, in vivo, animal models of tendon degeneration are mostly overuse models, where tendon damage is caused by a high number of load cycles. As a result, there is a lack of knowledge of how isolated overload leads to degeneration in tendons. A surgical model of synergist ablation (SynAb) overloads the target tendon, plantaris, by ablating its synergist tendon, Achilles. The objective of this study was to evaluate the structural and functional changes that occur following overload of plantaris tendon in a rat SynAb model. Tendon cross-sectional area (CSA) and shape changes were evaluated by longitudinal MR imaging up to 8 weeks postsurgery. Tissue-scale structural changes were evaluated by semiquantified histology and second harmonic generation microscopy. Fibril level changes were evaluated with serial block face scanning electron microscopy (SBF-SEM). Functional changes were evaluated using tension tests at the tissue and microscale using a custom testing system allowing both video and microscopy imaging. At 8 weeks, overloaded plantaris tendons exhibited degenerative changes including increases in CSA, cell density, collagen damage area fraction (DAF), and fibril diameter, and decreases in collagen alignment, modulus, and yield stress. To interpret the differences between overload and overuse in tendon, we introduce a new framework for tendon remodeling and degeneration that differentiates between the inputs of overload and overuse. In summary, isolated overload induces multiscale degenerative structural and functional changes in plantaris tendon.

Exercise for rotator cuff tendinopathy: Proposed mechanisms of recovery

Rotator cuff (RC) tendinopathy is a common recurrent cause of shoulder pain, and resistance exercise is the first-line recommended intervention. Proposed causal mechanisms of resistance exercise for patients with RC tendinopathy consist of four domains: tendon structure, neuromuscular factors, pain and sensorimotor processing, and psychosocial factors. Tendon structure plays a role in RC tendinopathy, with decreased stiffness, increased thickness, and collagen disorganization. Neuromuscular performance deficits of altered kinematics, muscle activation, and force are present in RC tendinopathy, but advanced methods of assessing muscle performance are needed to fully assess these factors. Psychological factors of depression, anxiety, pain catastrophizing, treatment expectations, and self-efficacy are present and predict patient-reported outcomes. Central nervous system dysfunctions also exist, specifically altered pain and sensorimotor processing. Resisted exercise may normalize these factors, but limited evidence exists to explain the relationship of the four proposed domains to trajectory of recovery and defining persistent deficits limiting outcomes. Clinicians and researchers can use this model to understand how exercise mediates change in patient outcomes, develop subgroups to deliver patient-specific approach for treatment and define metrics to track recovery over time. Supporting evidence is limited, indicating the need for future studies characterizing mechanisms of recovery with exercise for RC tendinopathy.

Achilles Tendon and Patellar Tendon Structure in Combat Soldiers Following Prevention Exercises

INTRODUCTION

Military training that increases physical stress on musculoskeletal morphology also increases the risk of orthopedic injuries. Somatosensory prevention programs that reduce stress and improve functionality could be beneficial for better organization of tendon structure. The aim of this study was to investigate the impact of a somatosensory prevention exercise on the tendon structure (percentage of echo-type fibers; A-P and M-L diameters and cross-sectional area) of the Achilles tendon and patellar tendon among combat soldiers.

MATERIALS AND METHODS

These tendons of male Infantry soldiers aged 18-21 were screened before and after a 14-week training course. The intervention group, who performed preventative exercises, included 108 soldiers (BMI = 23.85 ± 2.76), while the control group, who participated in the same military course without these exercises, included 98 soldiers (BMI = 24.26 ± 4.03). Ultrasound scanning for tendon structure included percent of echo-type I-IV fibers, A-P diameter, M-L diameter, and cross-sectional area parameters.

RESULTS

Time by group interaction was found for echo-type I and II in both tendons. No significant differences were found between the two groups in the pretesting percentage of echo-type IV fibers of the Achilles tendon (P = .522), in echo-type III fibers of the Achilles tendon (P = .833), and echo-type IV fibers of the patellar tendon (P = .162). Greater pre-post differences in echo-type III and IV fibers were found in the control group compared with the intervention group for both the Achilles tendon (P = .021, P = .002) and the patellar tendon (P < .001, P < .001).

CONCLUSION

Increased damaged fibers (echo-type III and IV) of both tendons were found among the control group, yet not among soldiers who performed prevention exercises.

Effects of Different Long-Term Exercise Modalities on Tissue Stiffness

Stiffness is a fundamental property of living tissues, which may be modified by pathologies or traumatic events but also by nutritional, pharmacological and exercise interventions. This review aimed to understand if specific forms of exercise are able to determine specific forms of tissue stiffness adaptations. A literature search was performed on PubMed, Scopus and Web of Science databases to identify manuscripts addressing adaptations of tissue stiffness as a consequence of long-term exercise. Muscular, connective, peripheral nerve and arterial stiffness were considered for the purpose of this review. Resistance training, aerobic training, plyometric training and stretching were retrieved as exercise modalities responsible for tissue stiffness adaptations. Differences were observed related to each specific modality. When exercise was applied to pathological cohorts (i.e. tendinopathy or hypertension), stiffness changed towards a physiological condition. Exercise interventions are able to determine tissue stiffness adaptations. These should be considered for specific exercise prescriptions. Future studies should concentrate on identifying the effects of exercise on the stiffness of specific tissues in a broader spectrum of pathological populations, in which a tendency for increased stiffness is observed.

Whole body vibration for chronic patellar tendinopathy: A randomized equivalence trial

Purpose: Whole body vibration (WBV) triggers anabolic responses in various tissues, including tendons, without requiring high force production. In this waitlist-controlled equivalence trial, we tested its clinical effectiveness as an alternative treatment for patellar tendinopathy against conventional heavy slow resistance training (HSR). Methods: Thirty-nine patients were randomized to either 3 months of WBV training (n = 13), HSR training (n = 11), or a waitlist control (WLC) group (n = 15). In a partly cross-over design, 14 patients of the WLC group were redistributed to one of the two intervention groups (5 in WBV, 9 in HSR). Pre- and post-intervention testing included pain assessments (VAS), functional limitations (VISA-P), knee extension strength and tendon morphological, mechanical and material properties. Follow-up measurements (VAS, VISA-P) were performed in the WBV and HSR groups 6 months after the intervention. Results: Comparisons with the WLC group revealed significant improvements in VISA-P and VAS scores after HSR (41%, p = 003; 54%, p = 0.005) and WBV (22%, p = 0.022; 56%, p = 0.031) training. These improvements continued until follow-up (HSR: 43%, 56%; WBV: 24%, 37%). Pre-post improvements in VAS scores were equivalent between WBV and HSR groups but inconclusive for the VISA-P score and all pre-test to follow up comparisons. The mid-tendon cross-sectional area was significantly reduced after WBV (-5.7%, p = 0.004) and HSR (-3.0%, p = 0.004) training compared to WLC although the equivalence test between interventions was inconclusive. Conclusion: Whole body vibration improved symptoms typically associated with patellar tendinopathy. This type of intervention is as effective as HSR against maximum pain, although equivalence could not be confirmed for other variables. The beneficial responses to WBV and HSR treatments persisted for 6 months after the end of the intervention. Clinical Trial Registration: https://www.drks.de/drks_web/setLocale_EN.do, identifier DRKS00011338.

Effects of Heavy Slow Resistance Training Combined With Corticosteroid Injections or Tendon Needling in Patients With Lateral Elbow Tendinopathy: A 3-Arm Randomized Double-Blinded Placebo-Controlled Study

BACKGROUND

Lateral elbow tendinopathy is a disabling tendon overuse injury. It remains unknown if a corticosteroid injection (CSI) or tendon needling (TN) combined with heavy slow resistance (HSR) training is superior to HSR alone in treating lateral elbow tendinopathy.

PURPOSE/HYPOTHESIS

The purpose was to investigate the effects of HSR combined with either (1) a CSI, (2) TN, or (3) placebo needling (PN) as treatment for lateral elbow tendinopathy. We hypothesized that 12 weeks of HSR in combination with a CSI or TN would have superior effects compared with PN at 12, 26, and 52 (primary endpoint) weeks' follow-up on primary (Disabilities of the Arm, Shoulder and Hand [DASH] score) and secondary outcomes in patients with chronic unilateral lateral elbow tendinopathy.

STUDY DESIGN

Randomized controlled trial; Level of evidence, 1.

METHODS

A total of 60 patients with chronic unilateral lateral elbow tendinopathy were randomized to perform 12 weeks of home-based HSR with elastic band exercises combined with either (1) a CSI, (2) TN, or (3) PN, and at 12, 26, and 52 weeks, we assessed the primary outcome, the DASH score, and secondary outcomes: shortened version of the DASH (QuickDASH) score, pain (numerical rating scale [NRS] score), pain-free grip strength, and hypervascularization (power Doppler area).

RESULTS

A CSI, TN, and PN improved patient outcomes equally based on the DASH (Δ20 points), QuickDASH (Δ21 points), and NRS (Δ2.5 points) scores after 12 weeks. Further, after 12 weeks, a CSI also resulted in decreased hypervascularization (power Doppler area) compared with PN (Δ-2251 pixels, P = .0418). Except for the QuickDASH score (CSI increased score by Δ15 points compared with PN; P = .0427), there were no differences between the groups after 52 weeks.

CONCLUSION

These results suggest that 12 weeks of HSR improved symptoms in both the short and the long term and that a CSI or TN did not amplify this effect. In addition, a CSI seemed to impair patient-reported outcomes compared with HSR alone at long-term follow-up.

REGISTRATION

NCT02521298 (ClinicalTrials.gov identifier).

Knee Extensor Mechanism Tendinopathy: Evaluation, Treatment, and Prevention

ABSTRACT

Knee extensor mechanism tendinopathy, including patellar and quadriceps tendinopathy, is common among athletes and those involved in jumping sports. It is largely a clinical diagnosis that presents as anterior knee pain and stiffness with associated tenderness over the affected tendon. Imaging modalities, including ultrasound and/or magnetic resonance imaging, may be helpful with the diagnosis of difficult cases or in the planning of interventional procedures. Focused and structured rehabilitation using eccentric or heavy slow resistance exercise in conjunction with load management is important for recovery. Adjuvant therapies (e.g., injections or surgery) may be necessary in recalcitrant cases or those with insufficient response to rehabilitation efforts. Prevention strategies focus on improving biomechanics, landing mechanism and lower-extremity balance, flexibility, and strength.

Blood Flow Restriction Resistance Training in Tendon Rehabilitation: A Scoping Review on Intervention Parameters, Physiological Effects, and Outcomes

Objective

To identify current evidence on blood flow restriction training (BFRT) in tendon injuries and healthy tendons, evaluating physiological tendon effects, intervention parameters, and outcomes.

Methods

This scoping review was reported in accordance with the PRISMA Extension for Scoping Reviews (PRISMA-ScR). Databases searched included MEDLINE, CINAHL, AMED, EMBase, SPORTDiscus, Cochrane library (Controlled trials, Systematic reviews), and five trial registries. Two independent reviewers screened studies at title/abstract and full text. Following screening, data was extracted and charted, and presented as figures and tables alongside a narrative synthesis. Any study design conducted on adults, investigating the effects of BFRT on healthy tendons or tendon pathology were included. Data were extracted on physiological tendon effects, intervention parameters and outcomes with BFRT.

Results

Thirteen studies were included, three on tendinopathy, two on tendon ruptures, and eight on healthy Achilles, patellar, and supraspinatus tendons. A variety of outcomes were assessed, including pain, function, strength, and tendon morphological and mechanical properties, particularly changes in tendon thickness. BFRT intervention parameters were heterogeneously prescribed.

Conclusion

Despite a dearth of studies to date on the effects of BFRT on healthy tendons and in tendon pathologies, preliminary evidence for beneficial effects of BFRT on tendons and clinical outcomes is encouraging. As BFRT is a relatively novel method, definitive conclusions, and recommendations on BFRT in tendon rehabilitation cannot be made at present, which should be addressed in future research, due to the potential therapeutic benefits highlighted in this review.

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.

Neuromechanical changes in Achilles tendinopathy and the effects of exercise-induced mechanical tendon loading: a protocol for a systematic review

INTRODUCTION

Achilles tendinopathy (AT) is a debilitating overuse injury characterised by pain, impaired functional performance, morpho-mechanical changes to the Achilles tendon and triceps surae neuromuscular alterations. Loading-based exercise has become the principal non-surgical choice for the treatment of AT; however, mechanistic evidence by which loading-based treatment may help to resolve tendon pain remains unclear. This systematic review aims to summarise the evidence of the neuromechanical changes produced by AT and by exercise-induced mechanical loading.

METHODS AND ANALYSIS

This systematic review protocol was informed and reported in accordance with the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA-P) and the Cochrane Handbook for Systematic Reviews of Interventions. Pubmed, MEDLINE, EMBASE, CINAHL Plus, Web of Science and SPORTDiscus electronic databases will be searched from inception to February 2021. Additionally, grey literature and key journals will be reviewed. Risk of bias will be determined independently by two reviewers using the version 2 of the Cochrane risk-of-bias tool for randomised trials (RoB 2) and the risk of bias in non-randomised studies - of interventions (ROBINS-I) tool according to Cochrane recommendations. Quality of the cumulative evidence will be assessed with the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) guidelines. If homogeneity exists between groups of studies, a random-effects meta-analysis will be conducted. If not, results will be synthesised narratively.

ETHICS AND DISSEMINATION

Our findings will be disseminated through publication in a peer-reviewed journal and presented at conferences. No ethical approval was required.

PROSPERO REGISTRATION NUMBER

CRD42021231933.

Novel interventions for recalcitrant patella tendinopathy: Results may favour autologous blood injection (ABI) over radial-extra-corporeal shockwave therapy (r-ESWT) - A prospective cohort study

BACKGROUND

Patella tendinopathy is a common condition in a number of sports and can have a significant impact on activity and quality of life. Whilst rehabilitation leads to improvements in the majority of cases, a number of adjunct treatments are available for resistant cases with limited evidence supporting the use of one treatment over another.Hypothesis/Purpose: To compare the outcomes for patients with chronic patella tendinopathy, following either radial-Extra-Corporeal Shockwave Therapy (r-ESWT) or Autologous Blood Injection (ABI).

STUDY DESIGN

Prospective cohort study.

METHODS

28 consecutive patients with chronic patella tendinopathy, treated with radial-ESWT (n = 14) or ABI (n = 14), with minimum three-month follow-up. Mean age 34.2 years, mean duration of symptoms 32.8 months. Patients received either three sessions of radial-Extra-Corporeal Shockwave Therapy (one session per week for 3 weeks), or two ultrasound-guided Autologous Blood Injections (2 injections performed 2-4 weeks apart). All patients received standardised after-care, including continuation of a structured home exercise programme of flexibility and progressive loading (eccentric strengthening) exercises. Main Outcome Measures were Victoria Institute of Sport - Patella questionnaire (VISA-P), plus 0-10 Visual Analogue Scale (VAS) for self-reported levels of "average pain".

RESULTS

There were statistically significant improvements in self-reported measures of pain/function following either procedure at 6-weeks and at 3-months, but only in the ABI group at 6-months. At 3-months: VISA-P was improved from 32.4% ± 11.7%-60.0% ± 20.7% (p < 0.01) in the ABI group, and from 34.2% ± 14.6%-48.9% ± 17.8% (p < 0.001) in the r-ESWT group.

CONCLUSIONS

Patients with chronic patella tendinopathy improved at 6-weeks and 3-months following either ABI or r-ESWT procedure, with significant benefits at 6-months seen only in the ABI group. Between group analysis demonstrated improved outcomes favouring ABI compared to r-ESWT at the 6-month timepoint using VISA-P, and at all time-points using VAS as outcome measures. The small sample sizes in this pragmatic study are however noted, which limit interpretation, and larger more robust studies are required to investigate this further. This pragmatic prospective cohort study demonstrates improvements following either r-ESWT or ABI procedures, with results potentially favouring ABI over r-ESWT for patients with chronic patella tendinopathy.

Current understanding of the diagnosis and management of the tendinopathy: An update from the lab to the clinical practice

Tendinopathy is labeled by many authors as a troublesome, common pathology, present in up to 30% medical care consultations involving musculoskeletal conditions. Despite the lasting interest for addressing tendon pathology, current researchers agree that even the exact definition of the term tendinopathy is unclear. Tendinopathy is currently diagnosed as a clinical hypothesis based on the patient symptoms and physical context. One of the main goals of current clinical management is to personalize treatment approaches to adapt them to the many different needs of the population. Tendons are complex structures that unite muscles and bones with two main objectives: to transmit forces and storage and release energy. Regarding the tensile properties of the tendons, several authors argued that tendons have higher tensile strength compared with muscles, however, are considered less flexible. Tendinopathy is an accepted term which is used to indicated a variety of tissue conditions that appear in injured tendons and describes a non-rupture damage in the tendon or paratendon, which is intensified with mechanical loading Even when the pathoetiology of tendinopathy is unclear, there is a wide array of treatments available to treat and manage tendinopathy. Although tendinitis usually debuts with an inflammatory response, the majority of chronic tendinopathies do not present inflammation and so the choosing of treatment should vary depending on severity, compliance, pain and duration of symptoms. The purpose of this article is to review and provide an overview about the currently research of the tendon diagnosis, management and etiology.

Rehabilitation After Gluteus Medius and Minimus Treatment

We reviewed the current literature regarding rehabilitation after gluteus medius and minimus tears as part of a conservative management or postoperative protocol. The greater trochanteric pain syndrome includes a constellation of pathologies that generate pain in the greater trochanteric region and may be accompanied by varying degrees of hip abductor disfunction. It may be related to tendinitis of the gluteus medius and minimus, greater trochanteric bursitis, or even formal tears of the hip abductor tendons. The initial management strategy of the hip abductor tears is conservative, including different anti-inflammatory therapies such as physical therapy and cortisone and platelet-rich plasma injections. The clearest indication for surgical management is failure of conservative management and loss of abductor muscle power. Surgical management has been performed both open and endoscopic with good reported clinical results. More severe tears typically require a more rigid and complex type of fixation. Exorcise intervention seem to improve symptoms after 4 months to a year of therapy therefore a very close supervision of the rehabilitation protocol is mandatory. Gluteus medius and minimus tears are frequent and may be not diagnosed timely. Treatment of these of lesions is based on the knowledge of pathomechanics involved and the extent of injury to the tendon and muscle tissue. Conservative management is based on protecting the hip abductor tendons from excessive tensile and compression stresses while applying progressive load in conjunction with physical and medical anti-inflammatory measures. Surgical treatment is indicated when conservative management fails or an abductor power deficit is associated with pain. Similar physical therapy protocols to those used in conservative management are used postoperatively.

Level of Evidence

Level V, expert opinion.

No Difference in Clinical Effects When Comparing Alfredson Eccentric and Silbernagel Combined Concentric-Eccentric Loading in Achilles Tendinopathy: A Randomized Controlled Trial

Background:

Alfredson isolated eccentric loading and Silbernagel concentric–eccentric loading have both shown beneficial effects on clinical symptoms in midportion Achilles tendinopathy (AT), but they have never been compared directly.

Purpose:

To test for differences in clinical effects at 1-year follow-up between Alfredson and Silbernagel loading in midportion AT.

Study Design:

Randomized controlled trial; Level of evidence, 2.

Methods:

A total of 40 recreational athletes were allocated to the Alfredson group (AG) or the Silbernagel group (SG). The primary outcome was the difference in the Victorian Institute of Sports Assessment–Achilles (VISA-A) at 1-year follow-up. Secondary outcomes were the visual analog scale for pain during activities of daily living (VAS-ADL) and sports activities (VAS–sports), the EuroQol 5 Dimensions instrument (EQ-5D), and global perceived effect score. Measurements were performed at baseline and 12-week, 26-week, and 1-year follow-up. Analysis was performed using a linear mixed-regression model with intervention (AG vs SG), time (12 weeks, 26 weeks, and 1 year postoperatively), and intervention-by-time interaction.

Results:

The VISA-A score improved for both AG and SG, from 60.7 ± 17.1 at baseline to 89.4 ± 13.0 at 1-year follow-up and from 59.8 ± 22.2 to 83.2 ± 22.4, respectively (P < .001 for both). Because the interaction term did not significantly improve the model, we reported a treatment effect without interaction term, indicating a constant difference at each follow-up. The linear mixed model with correction for baseline VISA-A and confounders revealed a nonsignificant treatment effect (2.4 [95% CI, –8.5 to 13.3]; P = .656). In addition, after adjustment for the respective baseline values and confounders, nonsignificant treatment effects were found for the VAS-ADL (–2.0 [95% CI, –11.3 to 7.3]; P = .665) and VAS-sports (1.3 [95% CI, –12.8 to 15.3], P = .858). The EQ-5D subscales improved in both groups. After 1 year, significantly more SG participants considered themselves improved (77.3% [SG] vs 50.0% [AG]; P = .04).

Conclusion:

No differences in clinical effects were found between Alfredson and Silbernagel loading at up to 1-year follow-up. Both programs significantly improved clinical symptoms, and given their high adherence rates, offering either of them as a home-based program with limited supervision appears to be an effective treatment strategy for midportion AT.

Registration:

NTR5638 (Netherlands Trial Register number).

Combined extracorporeal shockwave therapy and exercise for the treatment of tendinopathy: A narrative review

Tendinopathy is a chronic degenerative musculoskeletal disorder that is common in both athletes and the general population. Exercise and extracorporeal shockwave therapy (ESWT) is among the most common treatments used to mediate tendon healing and regeneration. The review presents the current understanding of mechanisms of action of ESWT and exercise in isolation and briefly synthesises evidence of their effectiveness for various tendinopathies. The central purpose of the review is to synthesize research findings investigating the combination of ESWT and exercise for five common tendinopathies (plantar heel pain, rotator cuff, lateral elbow, Achilles, and patellar tendinopathy) and provide recommendations on clinical applicability. Collectively, the available evidence indicates that ESWT combined with exercise in the form of eccentric training, tissue-specific stretching, or heavy slow resistance training are effective for specific tendinopathies and can therefore be recommended in treatment. Whilst there are at present a limited number of studies investigating combined EWST and exercise approaches, there is evidence to suggest that the combination improves outcomes in the treatment of plantar heel pain, Achilles, lateral elbow, and rotator cuff tendinopathy. However, despite overall positive outcomes in patellar tendinopathy, the combined treatment has not been shown at present to offer additional benefit over eccentric exercise alone.

The dispersion of viscoelastic properties of fascicle bundles within the tendon results from the presence of interfascicular matrix and flow of body fluids

In this work, we investigate differences in the mechanical and structural properties of tendon fascicle bundles dissected from different areas of bovine tendons. The properties of tendon fascicle bundles were investigated by means of uniaxial tests with relaxation periods and hysteresis, dynamic mechanical analysis (DMA), as well as magnetic resonance imaging (MRI). Uniaxial tests with relaxation periods revealed greater elastic modulus, hysteresis, as well as stress drop during the relaxation of samples dissected from the posterior side of the tendon. However, the normalized stress relaxation curves did not show a statistically significant difference in the stress drop between specimens cut from different zones or between different strain levels. Using dynamic mechanical analysis, we found that fascicle bundles dissected from the anterior side of the tendon had lower storage and loss moduli, which could result from altered fluid flow within the interfascicular matrix (IFM). The lower water content, diffusivity, and higher fractional anisotropy of the posterior part of the tendon, as observed using MRI, indicates a different structure of the IFM, which controls the flow of fluids within the tendon. Our results show that the viscoelastic response to dynamic loading is correlated with fluid flow within the IFM, which was confirmed during analysis of the MRI results. In contrast to this, the long-term relaxation of tendon fascicle bundles is controlled by viscoplasticity of the IFM and depends on the spatial distribution of the matrix within the tendon. Comparison of results from tensile tests, DMA, and MRI gives new insight into tendon mechanics and the role of the IFM. These findings may be useful in improving the diagnosis of tendon injury and effectiveness of medical treatments for tendinopathies.

Autoregulation in Resistance Training for Lower Limb Tendinopathy: A Potential Method for Addressing Individual Factors, Intervention Issues, and Inadequate Outcomes

Musculoskeletal disorders, such as tendinopathy, are placing an increasing burden on society and health systems. Tendinopathy accounts for up to 30% of musculoskeletal disorders, with a high incidence in athletes and the general population. Although resistance training has shown short-term effectiveness in the treatment of lower limb tendinopathy, more comprehensive exercise protocols and progression methods are required due to poor long-term outcomes. The most common resistance training protocols are predetermined and standardized, which presents significant limitations. Current standardized protocols do not adhere to scientific resistance training principles, consider individual factors, or take the importance of individualized training into account. Resistance training programs in case of tendinopathy are currently not achieving the required intensity and dosage, leading to high recurrence rates. Therefore, better methods for individualizing and progressing resistance training are required to improve outcomes. One potential method is autoregulation, which allows individuals to progress training at their own rate, taking individual factors into account. Despite the finding of their effectiveness in increasing the strength of healthy athletes, autoregulation methods have not been investigated in case of tendinopathy. The purpose of this narrative review was 3-fold: firstly, to give an overview and a critical analysis of the individual factors involved in tendinopathy and current resistance training protocols and their limitations. Secondly, to give an overview of the history, methods, and application of autoregulation strategies both in sports performance and physiotherapy. Finally, a theoretical adaptation of a current tendinopathy resistance training protocol using autoregulation methods is presented, providing an example of how the method could be implemented in clinical practice or future research.

Substantial Achilles adaptation following strength training has no impact on tendon function during walking

Tendons are responsive to mechanical loading and their properties are often the target of intervention programs. The tendon's mechanical properties, particularly stiffness, also govern its function, therefore changes to these properties could have substantial influence on energy-saving mechanisms during activities utilizing the stretch-shortening cycle. We investigated Achilles tendon (AT) function in vivo during walking with respect to a training intervention that elicited significant increases in AT stiffness. 14 men and women completed 12-weeks of isometric plantarflexor strength training that increased AT stiffness, measured during isometric MVC, by ~31%. Before and after the intervention, participants walked shod at their preferred velocity on a fully-instrumented treadmill. Movement kinematics, kinetics and displacement of the gastrocnemius medialis muscle-tendon junction were captured synchronously using 3D motion capture and ultrasound imaging, respectively. A MANOVA test was used to examine changes in AT force, stress, strain, stiffness, Young's modulus, hysteresis and strain energy, measured during walking, before and following strength training. All were non-significant for a main effect of time, therefore no follow-up statistical tests were conducted. Changes in joint kinematics, tendon strain, velocity, work and power and muscle activity during the stance phase were assessed with 1D statistical parametric mapping, all of which also demonstrated a lack of change in response to the intervention. This in vivo examination of tendon function in walking provides an important foundation for investigating the functional consequences of training adaptations. We found substantial increases in AT stiffness did not impact on tendon function during walking. AT stiffness measured during walking, however, was unchanged with training, which suggests that increases in stiffness may not be evident across the whole force-elongation relation, a finding which may help explain previously mixed intervention results and guide future investigations in the functional implications of tendon adaptation.

Mechanical properties and UTE-T2* in Patellar tendinopathy: The effect of load magnitude in exercise-based treatment

Loading intervention is currently the preferred management of tendinopathy, but to what extent different loading regimes influence the mechanical response in tendons is scarcely investigated. Therefore, the purposes of the investigation were to examine the effect of exercise interventions with either high or low load magnitude applied to the tendinopathic patellar tendon and the influence on its mechanical, material, and morphological properties. Forty-four men with chronic patellar tendinopathy were randomized to 12 weeks of exercising with either; 55% of 1RM throughout the period (MSR group) or 90% of 1RM (HSR group), and with equal total exercise volume in both groups. Mechanical (stiffness), material (T2* relaxation time), and morphological (cross-sectional area (CSA)) properties were assessed at baseline and after 12 weeks of intervention. MRI with ultra-short echo times (UTE) and T2*-mapping was applied to explore if T2* relaxation time could be used as a noninvasive marker for internal material alteration and early change thereof in response to intervention. There was no effect of HSR or MSR on the mechanical (stiffness), material (T2* relaxation time) or morphological (CSA) properties, but both regimes resulted in significant strength gain. In conclusion, there were no statistically superior effect of exercising with high (90%) compared to moderate (55%) load magnitude on the mechanical, material or morphological properties.

Maximum dorsiflexion increases Achilles tendon force during exercise for midportion Achilles tendinopathy

Rehabilitation is an important treatment for non-insertional Achilles tendinopathy. To date, eccentric loading exercises (ECC) have been the predominant choice; however, mechanical evidence underlying their use remains unclear. Other protocols, such as heavy slow resistance loading (HSR), have shown comparable outcomes, but with less training time. This study aims to identify the effect of external loading and other variables that influence Achilles tendon (AT) force in ECC and HSR. Ground reaction force and kinematic data during ECC and HSR were collected from 18 healthy participants for four loading conditions. The moment arms of the AT were estimated from MRIs of each participant. AT force then was calculated using the ankle torque obtained from inverse dynamics. In the eccentric phase, the AT force was not larger than in the concentric phase in both ECC and HSR. Under the same external load, the force through the AT was larger in ECC with the knee bent than in HSR with the knee straight due to increased dorsiflexion angle of the ankle. Multivariate regression analysis showed that external load and maximum dorsiflexion angle were significant predictors of peak AT force in both standing and seated positions. Therefore, to increase the effectiveness of loading the AT, exercises should apply adequate external load and reach maximum dorsiflexion during the movement. Peak dorsiflexion angle affected the AT force in a standing position at twice the rate of a seated position, suggesting standing could prove more effective for the same external loading and peak dorsiflexion angle.

Clinical Outcomes, Structure, and Function Improve With Both Heavy and Moderate Loads in the Treatment of Patellar Tendinopathy: A Randomized Clinical Trial

BACKGROUND

Loading interventions have become a predominant treatment strategy for tendinopathy, and positive clinical outcomes and tendon tissue responses may depend on the exercise dose and load magnitude.

PURPOSE/HYPOTHESIS

The purpose was to investigate if the load magnitude influenced the effect of a 12-week loading intervention for patellar tendinopathy in the short term (12 weeks) and long term (52 weeks). We hypothesized that a greater load magnitude of 90% of 1 repetition maximum (RM) would yield a more positive clinical outcome, tendon structure, and tendon function compared with a lower load magnitude of 55% of 1 RM when the total exercise volume was kept equal in both groups.

STUDY DESIGN

Randomized clinical trial; Level of evidence, 1.

METHODS

A total of 44 adult participants with chronic patellar tendinopathy were included and randomized to undergo moderate slow resistance (MSR group; 55% of 1 RM) or heavy slow resistance (HSR group; 90% of 1 RM). Function and symptoms (Victorian Institute of Sport Assessment-Patella questionnaire [VISA-P]), tendon pain during activity (numeric rating scale [NRS]), and ultrasound findings (tendon vascularization and swelling) were assessed before the intervention, at 6 and 12 weeks during the intervention, and at 52 weeks from baseline. Tendon function (functional tests) and tendon structure (ultrasound and magnetic resonance imaging) were investigated before and after the intervention period.

RESULTS

The HSR and MSR interventions both yielded significant clinical improvements in the VISA-P score (mean ± SEM) (HSR: 0 weeks, 58.8 ± 4.3; 12 weeks, 70.5 ± 4.4; 52 weeks, 79.7 ± 4.6) (MSR: 0 weeks, 59.9 ± 2.5; 12 weeks, 72.5 ± 2.9; 52 weeks, 82.6 ± 2.5), NRS score for running, NRS score for squats, NRS score for preferred sport, single-leg decline squat, and patient satisfaction after 12 weeks, and these were maintained after 52 weeks. HSR loading was not superior to MSR loading for any of the measured clinical outcomes. Similarly, there were no differences in functional (strength and jumping ability) or structural (tendon thickness, power Doppler area, and cross-sectional area) improvements between the groups undergoing HSR and MSR loading.

CONCLUSION

There was no superior effect of exercising with a high load magnitude (HSR) compared with a moderate load magnitude (MSR) for the clinical outcome, tendon structure, or tendon function in the treatment of patellar tendinopathy in the short term. Both HSR and MSR showed equally good, continued improvements in outcomes in the long term but did not reach normal values for healthy tendons.

REGISTRATION

NCT03096067 (ClinicalTrials.gov identifier).

Pain-guided activity modification during treatment for patellar tendinopathy: a feasibility and pilot randomized clinical trial

BACKGROUND

Activity modification is a key component of patellar tendinopathy treatment but there is a lack of evidence guiding activity modification prescription. Use of activity modification in treatment studies has varied widely and the impact of those recommendations has not been directly investigated or compared. The purpose of this study was to assess (1) the feasibility of using pain-guided activity modification during treatment for patellar tendinopathy and (2) if our outcome measures are responsive to changes in tendon health over the course of treatment.

METHODS

This was an unblinded, randomized two-arm pilot and feasibility study randomized clinical trial with parallel assignment, conducted in Newark, DE. Individuals between the ages of 16 and 40 years old with patellar tendinopathy were included. Participants were randomly assigned to a pain-guided activity (PGA) or pain-free activity (PFA) group using a spreadsheet-based randomization scheme. All participants received standardized treatment using a modified version of the heavy-slow resistance protocol 3×/week for 12 weeks. For the first 6 weeks, the PGA group used the Pain-Monitoring Model to guide activity outside of treatment and the PFA group was restricted from running, jumping, or activities that provoked their patellar tendon pain. Feasibility outcomes included recruitment, enrollment, randomization, compliance, and retention percentages. Clinical evaluations were conducted at baseline, 6, and 12 weeks to assess symptom severity, psychological factors, tendon morphology and mechanical properties, lower extremity function, and quadriceps muscle performance.

RESULTS

In a ~ 13-month period, 108 individuals were screened, 47/108 (43.5%) were eligible for participation, and 15/47 (32.0%) of those were enrolled (9 PGA, 6 PFA). The recruitment rate was 1.15 participants/month. The mean ± SD compliance with treatment was PGA: 86.1 ± 13.0% and PFA: 67.1 ± 30.7%. There was one missed evaluation session and two adverse events, which were not due to study interventions. Changes exceeding the smallest detectable change were observed for at least one outcome in each domain of tendon health.

CONCLUSIONS

Use of pain-guided activity modification during exercise therapy for patellar tendinopathy was found to be feasible, and the proposed outcome measures appropriate. Computer-based allocation concealment, blinding of evaluators, and greater recruitment of high-level athletes should be implemented in future trials.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT03694730 . Registered 3rd of October, 2018.

The Influence of a 14-Week Infantry Commanders Courses on the Achilles Tendon and Patellar Tendon Structure

INTRODUCTION

Alternated tendon structure may raise stress to the musculoskeletal structures and may increase the potential for overuse injury. Screening the tendon structure of soldiers pre- and post-participation in a strenuous combat course is essential. The aim of the present study was to investigate the influence of a 14-week infantry commanders courses on the Achilles tendon (AT) structure and patellar tendon (PT) structure in combat soldiers.

MATERIALS AND METHODS

Ninety-eight participants from an infantry commanders course were screened pre- and post-course for the AT and PT structures, using ultrasonographic tissue characterizaton (UTC) imaging to capture a 3D structure of four echo-type fibers (I-IV).

RESULTS

In both tendons, the mean relative frequency of echo-type I fibers significantly decreased from pre- to post-testing, with a significant increase in the relative frequency of echo-types II, III, and IV fibers. In the AT, 60.2% of the subjects showed positive differences (between pre- and post-testing in the echo-type III + IV fiber ("worsened" tendon structure), whereas in the PT, 92.2% of the subject showed an increased frequency. No significant correlation (r = 0.108; P = .324) was found between the differences of echo-type III + IV fibers of the AT and that of the PT.

CONCLUSIONS

Loads to the musculoskeletal structures along the combat course increased the mean relative frequency of the "reduced" echo-type fibers (III + IV) in both the AT structure and the PT structure. Yet, whereas in the AT around 40% of the soldiers showed an improved tendon structure along the course, in the PT less than 10% of the soldiers showed that improvement. Soldiers and commanders should be aware of the different influence of the loading exercises along the course on the AT and on the PT structure, as "reduced" tendons structure might put the soldiers at higher risk for injury in the future.

Tendinopathy

Tendinopathy describes a complex multifaceted pathology of the tendon, characterized by pain, decline in function and reduced exercise tolerance. The most common overuse tendinopathies involve the rotator cuff tendon, medial and lateral elbow epicondyles, patellar tendon, gluteal tendons and the Achilles tendon. The prominent histological and molecular features of tendinopathy include disorganization of collagen fibres, an increase in the microvasculature and sensory nerve innervation, dysregulated extracellular matrix homeostasis, increased immune cells and inflammatory mediators, and enhanced cellular apoptosis. Although diagnosis is mostly achieved based on clinical symptoms, in some cases, additional pain-provoking tests and imaging might be necessary. Management consists of different exercise and loading programmes, therapeutic modalities and surgical interventions; however, their effectiveness remains ambiguous. Future research should focus on elucidating the key functional pathways implicated in clinical disease and on improved rehabilitation protocols.

IN-SEASON REHABILITATION PROGRAM USING BLOOD FLOW RESTRICTION THERAPY FOR TWO DECATHLETES WITH PATELLAR TENDINOPATHY: A CASE REPORT

Background and Purpose

Patellar tendinopathy is an overuse injury experienced primarily by athletes; especially athletes who participate in sports that involve frequent jumping. Therapeutic exercise is the primary conservative treatment for patients with this condition. However, some patients with patellar tendinopathy may be unable to tolerate the loading that occurs during exercise. The use of blood flow restriction (BFR) therapy for patients with patellar tendinopathy may allow the athlete to exercise with a lower load while still experiencing the physiological benefits associated with training at a higher intensity. The purpose of this case report was to detail the outcomes from a rehabilitation program utilizing BFR for two collegiate decathletes with patellar tendinopathy.

Study Design

Case ReportCase Descriptions and Interventions: Two NCAA Division III freshmen collegiate decathletes with a history of left knee pain prior to college and who had been complaining of increasing pain during the initial month of track practices. Findings from the musculoskeletal examinations included left sided lower extremity weakness, pain during functional testing, pain when palpating the left patellar tendon, and VISA-P scores less than 80. Ultrasound imaging at baseline revealed thickened tendons on the left with hypoechoic regions. Both athletes participated in 20 therapy sessions consisting of therapeutic exercises performed with BFR.

Outcomes

Both athletes experienced improvements in pain scores, increases in lower extremity strength, improved functional test performance, higher VISA-P scores, and improvements in tendon size and appearance as measured by diagnostic ultrasound.

Conclusion

Both athletes experienced improvements with the BFR-based therapeutic exercise program and were able to compete throughout the track season. The use of BFR may allow patients who are unable to tolerate exercise due to pain an alternative approach during rehabilitation. Future research should compare therapeutic exercise programs for this condition with and without BFR.

Level of Evidence

Level V.

Recent advances in tendinopathy

Tendinopathy refers to the clinical diagnosis of activity-related pain resulting in a decline in tendon function. In the last few years, much has been published concerning the basic science and clinical investigation of tendinopathy and debates and discussions to new questions and points of view started many years ago. This advances review will discuss the current thinking on the basic science and clinical management of tendinopathy and in particular new findings in the tendon repair space that are relevant to the pathophysiology of tendinopathy. We will further discuss potential novel therapies on the horizon in human tendon disease.

The influence of a multidisciplinary intervention program on Achilles tendon structure in children with overweight and obesity

The effects of childhood obesity on tendon structure and its relation to physical activity are barely known. We aimed to investigate the influence of a 6-month multidisciplinary childhood obesity management program (which included dietary intervention and an exercise program) on Achilles tendon structure in overweight/obese children. Twenty-five overweight/obese children (overweight group) who participated in a 6-month multidisciplinary childhood obesity program, and 27 normal-weight controls were examined for anthropometric measurements and for Achilles tendon structure (using ultrasound tissue characterization to capture a three-dimensional structure of four echo type fibers and the cross-sectional area) at baseline, 3, and 6 months. The BMI of the overweight group significantly decreased from the pre- to the post-intervention period, (p = .002, η² = .229), yet among the control group, the BMI significantly increased (p = .002, η² = .222). Interactions (pre-post × group) showed a significant decrease in the prevalence of echo type I and in echo type III fibers and a significant increase in the prevalence of echo type II fibers and in the cross-sectional area along the intervention. No significant changes in echo type fibers were found in the control group along the 6 months.Conclusion: At pre-intervention, the overweight group had significantly "worse" tendon structure, with a lower prevalence of echo type II fiber and a higher prevalence of echo type III fibers compared with the control group. Following the 6-month intervention, the tendon structure of the overweight group was "positively" changed, with reduced echo type III fibers and increased echo type II fibers. What is Known: • Physical activity and weight reduction programs are efficient for obese children. • Obese children tend to suffer orthopedic problems and pain during physical activity. What is New: • Pre-intervention, obese children had 'worse' tendon structure compared to controls. • Following 6-month program, tendon structure of obese children 'positively' changed.

THE MANAGEMENT OF PROXIMAL HAMSTRING TENDINOPATHY IN A COMPETITIVE POWERLIFTER WITH HEAVY SLOW RESISTANCE TRAINING - A CASE REPORT

Background and Purpose

Proximal hamstring tendinopathy is a chronic, overuse condition that commonly develops in athletes. Eccentric exercise has been widely accepted in the clinic as the treatment of choice for the management of tendinopathies. However, this form of treatment has seldom been compared to other forms of load-based management for hamstring tendinopathies. Heavy slow resistance training, which consists of both concentric and eccentric phases, increases the loading time experienced by the tendon compared to eccentric only exercises. Heavy slow resistance training has achieved positive clinical results in the management of Achilles and patellar tendinopathy.

Purpose

The purpose of this case report is to describe the outcomes of a powerlifter with proximal hamstring tendinopathy who responded favorably to a heavy slow resistance biased rehabilitation program after traditional, conservative management failed to alleviate symptoms.

Case Description

A 31-year-old male competitive powerlifter was seen in physical therapy for the management of proximal hamstring tendinopathy. The subject had experienced long duration pain localized at the ischial tuberosity combined with hip weakness that limited his ability to lift weigtht and sit for longer than 30 minutes. Treatment included a 12-week heavy slow resistance program with the focus of increasing load intensity.

Outcomes

Numeric pain-rating scale was assessed at baseline, after a 12-week heavy slow resistance protocol, and 12 months post protocol. Within four weeks of starting the heavy slow resistance program, the subject noted a meaningful decrease in pain. The subject experienced clinically important improvements in numeric pain-rating scale immediately after the protocol and these improvements remained 12 months after completing the protocol. The subject was able to return to competitive powerlifting after the 12-week program.

Discussion

A meaningful change in pain occurred within four weeks of starting the program and continued improvement throughout the remainder of the 12 weeks with outcomes maintained 12 months after completing the program suggests that increasing the loading strategy with a heavy slow resistance program was helpful for this subject.

Level of Evidence

4.

Quantitative Analysis of Patellar Tendon After Total Knee Arthroplasty Using Echo Intensity: A Nonrandomized Controlled Trial of Alpine Skiing

BACKGROUND

Despite the knee extensor weakness, less attention has been paid to the evaluation of patellar tendon after total knee arthroplasty (TKA). We previously observed patellar tendon hypertrophy after TKA. The purpose of this study is to reanalyze these ultrasound data to detect whether brightness mode ultrasound imaging reflects pathological changes of the patellar tendon after TKA.

METHODS

Twenty-eight participants with post unilateral TKA were assigned to an intervention group or control group. The intervention group underwent a 12-week skiing program. Patellar tendon mechanical properties were obtained by combining isometric dynamometry, ultrasound imaging, and electromyography in operated knee and nonoperated knee. Luminosity ratio (LR) was measured using echo intensity in a relaxed and maximally loaded phase.

RESULTS

Baseline comparisons revealed significant effects of the surgical side (P < .001) and loading phase (P = .017), but no interaction between leg and phase (P < .149). LR of the operated knee was significantly lower than LR of the nonoperated knee in relaxed (P < .001) and maximally loaded phases (P = .003). In addition, there was a significant correlation between LR of maximum phase and isometric knee extension torque (r² = 0.156, P = .038). However, LR was not related to patellar tendon stiffness, Young's modulus, or strain. There was a significant time effect in knee extension torque, but no time effects on LR and tendon force.

CONCLUSION

Patellar tendon LR is decreased along with degenerative change after TKA. Ultrasound imaging provides a promising metric to acquire in vivo patellar tendon pathological assessment after TKA.

Association Between Clinical and Imaging Outcomes After Therapeutic Loading Exercise in Patients Diagnosed With Achilles or Patellar Tendinopathy at Short- and Long-Term Follow-up: A Systematic Review

OBJECTIVE

To determine the association between clinical and imaging outcomes after therapeutic loading exercise in Achilles tendinopathy (AT) and patellar tendinopathy (PT) populations at both short- and long-term follow-up.

DATA SOURCES

The PUBMED and EMBASE databases were searched (up to June 2017) to identify articles that meet the inclusion criteria: (1) patients diagnosed with AT (insertional or midportion) or PT; (2) rehabilitation based on therapeutic loading exercise; and (3) assessment of clinical outcomes and tendon structure using an imaging modality.

MAIN RESULTS

Two independent reviewers screened 2894 search results, identifying 21 suitable studies. According to the studies included in this review, clinical results showed significant improvements for patients with AT and PT after eccentric exercise (ECC) and heavy slow resistance (HSR) at short- and long-term follow-up. Imaging outcomes were not consistent. Moderate-to-strong evidence for patients with AT suggested an association between clinical outcomes and imaging outcomes (tendon thickness and tendon neovascularization) after ECC at long-term follow-up. For patients with PT, there was moderate evidence supporting an association between clinical outcomes (questionnaire score and pain) and imaging (tendon thickness and tendon neovascularization) after ECC at short-term follow-up. For both the AT and PT groups, there was moderate evidence for an association between clinical outcomes and tendon thickness and neovascularization after HSR exercise. Results related to the HSR exercise should be interpreted with caution because of the small number of studies.

CONCLUSIONS

Based on the findings of the present review, the use of imaging outcomes as a complementary examination to the clinical assessment was confirmed. Overall, an improvement in clinical outcomes seems to be associated with a reduction in tendon thickness and tendon neovascularization. Clinicians should be aware that during the interpretation of the imaging outcomes, factors such as tendinopathy location, exercise modality performed, and a follow-up period should be considered.

Immediate and Short-Term Effects of Short- and Long-Duration Isometric Contractions in Patellar Tendinopathy

OBJECTIVES

Isometric muscle contractions are used in the management of patellar tendinopathy to manage pain and improve function. Little is known about whether long- or short-duration contractions are optimal to improve pain. This study examined the immediate and short-term (4 weeks) effects of long- and short-duration isometric contraction on patellar tendon pain, and tendon adaptation.

DESIGN

Repeated measures within groups.

SETTING

Clinical primary care.

PATIENTS

Participants (n = 16, males) with patellar tendinopathy.

INTERVENTION

Short-duration (24 sets of 10 seconds) or long-duration (6 sets of 40 seconds) isometric knee extension loading (85% maximal voluntary contraction), for 4 weeks.

MAIN OUTCOME MEASURE

Immediate change in pain with single-leg decline squat (SLDS) and hop, as well as change in pain and tendon adaptation [within-session anterior-posterior (AP) strain] were assessed over 4 weeks.

RESULTS

Pain was significantly reduced after isometric loading on both SLDS (P < 0.01) and hop tests (P < 0.01). Pain and quadriceps function improved over the 4 weeks (P < 0.05). There was significant AP strain at each measurement occasion (P < 0.01). Although transverse strain increased across the training period from ∼14% to 22%, this was not significant (P = 0.08).

CONCLUSIONS

This is the first study to show that short-duration isometric contractions are as effective as longer duration contractions for relieving patellar tendon pain when total time under tension is equalized. This finding provides clinicians with greater options in prescription of isometric loading and may be particularly useful among patients who do not tolerate longer duration contractions. The trend for tendon adaptation over the short 4-week study period warrants further investigation.

Mechanical and Material Tendon Properties in Patients With Proximal Patellar Tendinopathy

Introduction

The effect of chronic patellar tendinopathy on tissue function and integrity is currently unclear and underinvestigated. The aim of this cohort comparison was to examine morphological, material, and mechanical properties of the patellar tendon and to extend earlier findings by measuring the ability to store and return elastic energy in symptomatic tendons.

Methods

Seventeen patients with chronic (>3 months, VISA-P < 80), inferior pole patellar tendinopathy (24 ± 4 years; male = 12, female = 5) were carefully matched to controls (25 ± 3 years) for training status, pattern, and history of loading of the patellar tendon. Individual knee extension force, patellar tendon stiffness, stress, strain, Young’s modulus, hysteresis, and energy storage capacity, were obtained with combined dynamometry, ultrasonography, magnetic resonance imaging, and electromyography.

Results

Anthropometric parameters did not differ between groups. VISA-P scores ranged from 28 to 78 points, and symptoms had lasted from 10 to 120 months before testing. Tendon proximal cross-sectional area was 61% larger in the patellar tendinopathy group than in the control group. There were no differences between groups in maximal voluntary isometric knee extension torque (p = 0.216; d < −0.31) nor in tensile tendon force produced during isometric ramp contractions (p = 0.185; d < −0.34). Similarly, tendon strain (p = 0.634; d < 0.12), hysteresis (p = 0.461; d < 0.18), and strain energy storage (p = 0.656; d < 0.36) did not differ between groups. However, patellar tendon stiffness (−19%; p = 0.007; d < −0.74), stress (−27%; p< 0.002; d < −0.90) and Young’s modulus (−32%; p = 0.001; d < −0.94) were significantly lower in tendinopathic patients compared to healthy controls.

Discussion

In this study, we observed lower stiffness in affected tendons. However, despite the substantial structural and histological changes occurring with tendinopathy, the tendon capacity to store and dissipate energy did not differ significantly.