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The implementation of resistance training principles in exercise interventions for lower limb tendinopathy: A systematic review

Burton, I. and McCormack, A., 2021. The implementation of resistance training principles in exercise interventions for lower limb tendinopathy: A systematic review. Physical Therapy in Sport, 50, pp.97-113.

In today’s letter

• A short summary of the research looking at resistance training implementation in lower limb tendinopathies

• Rapid Results = The main way to implement resistance training into rehab is by first understanding

  a) Patient history/time of discomfort

  b) Sport specific demands

  c) Patients goals & time availability to commit to specific training regime

• Top 3 reads to check out: to further your knowledge about = Tendininopathies

• Dank meme! Is your patient complaining that physio isn’t working ? 😃 

Aim of study

1. The primary purpose of this systematic review was to examine the current literature on resistance training interventions for lower limb tendinopathies and evaluate the proportion of studies that reported and implemented key resistance training principles (specificity, progression, overload, individualisation) and reported relevant prescription components (frequency, intensity, sets, repetitions).

2. A secondary objective was to evaluate the proportion of studies that reported and implemented intervention adherence.

Background

• Plantar heel pain is prevalent in 18% of runners, while Achilles and patellar tendinopathy rates reach up to 23% and 45%, respectively, in runners and elite male volleyball players.

• Exercise, especially various forms of resistance training, is commonly recommended for treatment; however, only moderate long-term effectiveness in improving pain and function has been demonstrated.

• The response to resistance training depends on factors like tendinopathy type and stage, duration, individual intrinsic and extrinsic factors (e.g., sensory processing, age), and exercise parameters (type, dose, duration, frequency, volume, and intervention adherence).

• Applying a generic and standardised resistance training approach to a diverse tendinopathy population may limit its potential utility for improving outcomes

Results

• 52 studies analysed | Achilles tendinopathy was the most common tendinopathy investigated (26 studies), followed by patellar (16), plantar heel (4), gluteal (3), and tibialis posterior (3).

• Eccentric resistance training (40 studies) was the most common resistance training type investigated, with concentric (3), isometric (3), isotonic (3) heavy slow resistance (7) and combined or general training approaches (4) also looked into.

• Training interventions varied in duration from 4 to 26 weeks, with a predominant 85% of studies employing a 12-week duration.

• All studies incorporated outcome measures assessing pain and function, along with additional measures like quality of life and tendon structure through ultrasonography.

• The principle of specificity was universally applied in all studies (100%), directing resistance training to the pathological tendon with the goal of enhancing pain and function.

Discussion

Eccentric exercise

• Eccentric resistance training, introduced through the Alfredson protocol in 1998, has dominated conservative interventions for lower limb tendinopathies in the last two decades.

• In concentric contractions, muscles shorten during contraction, whereas eccentric contractions involve the muscle lengthening.

• Isotonic contractions combine both concentric and eccentric movements, while isometric contractions maintain a static muscle length without change.

• Plyometric exercises like jumping and hopping rely on reactive strength, where muscles store and release energy rapidly.

• Despite the positive effects of eccentric contractions in treating tendinopathies, there's currently no strong evidence supporting the reduction or elimination of concentric contractions for chronic tendinopathies

• Alfredson's initial success with an athletic cohort doesn't guarantee positive outcomes for all patients; research by Sayana and Maffulli (2007) found that 45% of patients deemed eccentric training unsuccessful based on pain and function outcomes, suggesting it may not be suitable for everyone.

Heavy slow resistance training

• Heavy Slow Resistance Training (HSRT) has gained popularity in both research and clinical practice as an alternative to the Alfredson eccentric protocol.

• Unlike the strict 180 daily repetitions in the Alfredson protocol, HSRT aligns more with scientific training principles, incorporating progressive load and volume increases, consistent time under tension, and extended rest periods.

• Recent evidence suggests that HSRT may yield superior clinical outcomes and greater patient satisfaction compared to isolated eccentric training for lower limb tendinopathies.

• Despite its advantages, HSRT protocols often fall short of intended dosage levels due to insufficient loading progression, indicating the need for better methods and a more individualised approach.

• The implementation of the overload principle in resistance training pushes biological tissues beyond their current thresholds, promoting adaptations and increasing tolerance to subsequent stresses, potentially reducing the risk of future injuries.

Tendon healing

• There's a current lack of evidence pinpointing which factors in resistance training interventions have a significant impact on outcomes.

• Positive effects and adaptations in tendons require high-intensity resistance training with gradual increases in loading.

• The substantial forces and loads generated during deliberate concentric and eccentric contractions can stimulate tendon remodeling and compliance through collagen synthesis and reduced neovascularisation, particularly when applied progressively.

• Exercise, through mechano-transduction, has the potential to influence cell homeostasis and may stimulate the regeneration of tendons.

Loading principles

• There's a question about whether many published studies truly focus on strength training or if they might be better categorised as active stretching with relatively low-intensity eccentric movement.

• Recent evidence indicates that to bring about changes in tendon properties, including mechanical, material, and morphological changes, an intensity threshold above 70% of maximum is necessary.

• Current protocols often involve high repetition volume and insufficient loading, making it doubtful that this required intensity is being achieved, potentially contributing to less favorable outcomes.

• Very slow repetitions (usually lasting 6-8 seconds) at a high repetition volume might also result in reduced intensity, raising concerns about their effectiveness.

• An improved approach could involve fewer repetitions at a higher load, with increased sets while maintaining the slow tempo seen in heavy slow resistance training. This approach, known as 'cluster training,' may help sustain sufficient intensity and volume.

Top 3 reads

Check these out to get a better understanding of tendonopthies

1. Managing patellar tendinopathy in season -

   https://www.sportsmith.co/articles/managing-patellar-tendinopathy-in-season/

2. Achilles Tendinopathy: Assessment & Treatment

   https://sportsmedu.com/2023/10/12/achilles-tendinopathy-assessement/

3. Treatment of Tendinopathy: What Works, What Does Not, and What is on the Horizon

   https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2505250/

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