Eccentric Exercise for Achilles Tendinopathy: A Narrative Review and Clinical Decision-Making Considerations

Effect of Eccentric Exercise on Metabolic Health in Diabetes and Obesity

There is a growing body of evidence showing the importance of physical activity against civilization-induced metabolic diseases, including type 2 diabetes (T2DM) and obesity. Eccentric contraction, when skeletal muscles generate force by lengthening, is a unique type of skeletal muscle activity. Eccentric contraction may lead to better power production characteristics of the muscle because eccentric contraction requires less energy and can result in higher tension. Therefore, it is an ideal tool in the rehabilitation program of patients. However, the complex metabolic effect (i.e., fat mass reduction, increased lipid oxidation, improvement in blood lipid profile, and increased insulin sensitivity) of the eccentric contraction alone has scarcely been investigated. This paper aims to review the current literature to provide information on whether eccentric contraction can influence metabolic health and body composition in T2DM or obesity. We also discussed the potential role of myokines in mediating the effects of eccentric exercise. A better understanding of the mechanism of eccentric training and particularly their participation in the regulation of metabolic diseases may widen their possible therapeutic use and, thereby, may support the fight against the leading global risks for mortality in the world.

Identifying characteristics of resistance-based therapeutic exercise interventions for Achilles tendinopathy: A scoping review

OBJECTIVE

This scoping review describes resistance-based therapeutic exercise intervention characteristics for Achilles tendinopathy (AT) treatment (e.g., therapeutic dose, underlying mechanisms targeted by exercise) and assesses participant reporting characteristics.

METHODS

Seven electronic databases were searched; studies delivering a resistance exercise-focused treatment for individuals with AT were included. The Template for Intervention Description and Replication (TIDieR) and the ICON 2019 'Recommended standards for reporting participant characteristics in tendinopathy research' checklists framed data extraction, and study quality was assessed using the Mixed Methods Appraisal Tool 2018 version.

RESULTS

68 publications (describing 59 studies and 72 exercise programs) were included. Results demonstrate that therapeutic exercise interventions for AT are well reported according to the TIDieR checklist, and participant characteristics are well reported according to the ICON checklist. Various underlying therapeutic mechanisms were proposed, with the most common being increasing tendon strength, increasing calf muscle strength, and enhancing collagen synthesis.

CONCLUSIONS

While evidence suggests that resistance-based therapeutic exercise interventions are effective in treating AT, more reporting on program fidelity, adherence, and compliance is needed. By summarizing currently published AT exercise programs and reporting key intervention characteristics in a single location, this review can assist clinicians in developing individualized resistance training programs for people with AT.

Eccentric Exercise: Adaptations and Applications for Health and Performance

The goals of this narrative review are to provide a brief overview of the muscle and tendon adaptations to eccentric resistance exercise and address the applications of this form of training to aid rehabilitative interventions and enhance sports performance. This work is centered on the author contributions to the Special Issue entitled "Eccentric Exercise: Adaptations and Applications for Health and Performance". The major themes from the contributing authors include the need to place greater attention on eccentric exercise mode selection based on training goals and individual fitness level, optimal approaches to implementing eccentric resistance exercise for therapeutic purposes, factors that affect the use of eccentric exercise across the lifespan, and general recommendations to integrate eccentric exercise in athletic training regimens. The authors propose that movement velocity and the absorption or recovery of kinetic energy are critical components of eccentric exercise programming. Regarding the therapeutic use of eccentric resistance training, patient-level factors regarding condition severity, fitness level, and stage of rehabilitation should govern the plan of care. In athletic populations, use of eccentric exercise may improve movement competency and promote improved safety and performance of sport-specific tasks. Eccentric resistance training is a viable option for youth, young adults, and older adults when the exercise prescription appropriately addresses program goals, exercise tolerability, and compliance. Despite the benefits of eccentric exercise, several key questions remain unanswered regarding its application underscoring the need for further investigation.

Muscle and tendon adaptations to moderate load eccentric vs. concentric resistance exercise in young and older males

Resistance exercise training (RET) is well-known to counteract negative age-related changes in both muscle and tendon tissue. Traditional RET consists of both concentric (CON) and eccentric (ECC) contractions; nevertheless, isolated ECC contractions are metabolically less demanding and, thus, may be more suitable for older populations. However, whether submaximal (60% 1RM) CON or ECC contractions differ in their effectiveness is relatively unknown. Further, whether the time course of muscle and tendon adaptations differs to the above is also unknown. Therefore, this study aimed to establish the time course of muscle and tendon adaptations to submaximal CON and ECC RET. Twenty healthy young (24.5 ± 5.1 years) and 17 older males (68.1 ± 2.4 years) were randomly allocated to either isolated CON or ECC RET which took place 3/week for 8 weeks. Tendon biomechanical properties, muscle architecture and maximal voluntary contraction were assessed every 2 weeks and quadriceps muscle volume every 4 weeks. Positive changes in tendon Young's modulus were observed after 4 weeks in all groups after which adaptations in young males plateaued but continued to increase in older males, suggesting a dampened rate of adaptation with age. However, both CON and ECC resulted in similar overall changes in tendon Young's modulus, in all groups. Muscle hypertrophy and strength increases were similar between CON and ECC in all groups. However, pennation angle increases were greater in CON, and fascicle length changes were greater in ECC. Notably, muscle and tendon adaptations appeared to occur in synergy, presumably to maintain the efficacy of the muscle-tendon unit.

Physical therapy for tendinopathy: An umbrella review of systematic reviews and meta-analyses

OBJECTIVE

To summarize evidence in the last decade regarding the efficacy of physical therapy interventions to treat tendinopathy, as a single disease entity, as determined in systematic reviews (SRs) and/or meta-analyses (MAs).

METHODS

Electronic search of PubMed, PEDro, and Scopus database was performed from year 2010 to January 2020. The methodological quality of the identified studies was assessed using the AMSTAR 2 tool. Studies scoring 9 points or higher were further analyzed using GRADE principles.

RESULTS

40 SRs and/or MAs were included in qualitative synthesis, whereas only 5 MAs were included in quantitative synthesis. Low-level laser therapy (LLLT) intervention showed a pooled improvement in pain reduction of 1.53 cm; 95% CI, [1.14, 1.91] (I² = 1.9%, p = 0.361) on visual analogue scale, and grip strength of 9.59 kg; 95% CI, [5.90, 13.27].

CONCLUSIONS

Moderate-quality evidence may support these following interventions: LLLT revealed a statistically and potentially clinically significant improvement in pain and function on the short-term. Extracorporeal shockwave therapy showed a statistically significant enhancement in pain and function at all follow-up durations; however, its clinical significance was undetermined. Eccentric exercise was supported by qualitative evidence only. Caution is advised when interpreting results due to possible pathological differences in tendinopathy at each region.

Multifaceted Exercise Prescription in the Management of an Overhead Athlete with Suspected Distal Biceps Tendinopathy: A Case Report

BACKGROUND AND PURPOSE

Distal biceps brachii tendinopathy is an uncommon diagnosis. Various exercise prescriptions have demonstrated efficacy in the management of tendinopathy, although studies frequently focus on the effects of a specific type of muscular contraction (i.e., concentric, isometric, or eccentric). Currently, there is limited research guiding the conservative management of distal biceps tendinopathy, particularly with overhead athletes, and even less evidence reporting a multifaceted exercise prescription for individuals with tendinopathy. The purpose of this case report is to describe the integration of various modes of therapeutic exercise into a rehabilitation program for an overhead athlete with suspected distal biceps brachii tendinopathy.

CASE DESCRIPTION

A 19-year-old male collegiate baseball pitcher presented to an outpatient physical therapy clinic via direct access for left antecubital pain, which began 6 weeks prior to the evaluation while pitching during try-outs. Following physical examination, distal biceps tendinopathy was the likely clinical diagnosis. Interventions focused on early eccentric exercise eventually progressing to concentric and plyometric activity for return to sport.

OUTCOMES

The patient was seen five times over the course of 4 weeks. He had significant improvements of pain, patient-reported functional outcomes, global rating of change, strength, tenderness, and provocation testing. The patient was able to return to an off-season pitching program.

DISCUSSION

An impairment-based and task-specific exercise prescription was effective for this patient with distal biceps tendinopathy. Understanding the biomechanical demands of an individual's functional limitation, in this case baseball pitching, may assist the decision-making process and optimize outcomes. Additional research into the most effective exercise prescriptions for individuals with uncommon tendinopathies is warranted.

Tendon Adaptations to Eccentric Exercise and the Implications for Older Adults

The purpose of this short review is to discuss the effects of eccentric exercise in modifying the properties of tendon tissue in healthy individuals. The tendon provides a mechanical link between muscle and bone, allowing force transmission to the skeleton, and thus, its properties have significant functional implications. Chronic resistance training has long been shown to increase the stiffness and Young's modulus of the tendon and even tendon cross-sectional area. However, as the tendon responds to the amount and/or frequency of strain, it has been previously suggested that eccentric training may result in greater adaptations due to the potential for greater training loads. Thus, this review discusses the effects of eccentric training upon healthy tendon tissue and compares these to other training modalities. Furthermore, it has been reported that the tendon may undergo adverse age-related changes. Thus, this review also discusses the potential application of eccentric resistance training as a preferential modality for counteracting these age-related changes. We conclude that while there may be no difference between contraction types for overall tendon adaptation, the lower demands of eccentric contractions may make it more appealing for the elderly population.

Conservative Treatment of Chronic Achilles Tendinopathy: A Systematic Review

Achilles tendinopathy is a common musculoskeletal disorder. Athletes, runners and jumpers, and the sedentary are frequently affected. Numerous are the therapeutic choices to manage these kinds of disorders. The aim of this review is to analyze the available literature to document the up-to-date evidence on conservative management of Achilles tendinopathy. A systematic review of two medical electronic databases was performed by three independent authors, using the following inclusion criteria: conservative treatment consisted of pharmacologic, physical therapy without operative treatment, with more of 6 months symptoms and a minimum average of 6-months follow-up. Studies of any level of evidence, reporting clinical results, and dealing with Achilles tendinopathy and conservative treatment were searched for. A total of n = 1228 articles were found. At the end of the first screening, following the previously described selection criteria, we selected n = 94 articles eligible for full-text reading. Ultimately, after full-text reading and a reference list check, we selected n = 29 articles. Achilles tendinopathy is a frequent musculoskeletal disorder and several conservative treatments have been proposed, but no therapy is universally accepted, except for eccentric exercise training, which is the gold standard and a commonly used protocol.