Train ECCENTRICS for shoulder Rehab! Part 1 The Basics!

Physiotherapists have long used muscular rehabilitation as a method to optimise performance and to reduce pain in patients with impairments of the shoulder region. Recent years has seen a rise of isomeric exercise for rotator cuff related conditions because of its role in muscle performance and pain modulation. Prior to this the main therapeutic intervention for muscular rehabilitation was concentric related exercise modalities in spite of evidence and a theoretical rational to support eccentric exercise. If eccentric exercise is used it all it is reserved for the late stages of rehabilitation. This may be short sighted.

So why is eccentrics exercise a viable intervention.

Well, firstly we should define want an eccentric muscle action is!

“ In short it is a muscle contraction in which the muscle lengthens while under load”.

Mathematically, an eccentric muscle action is negative work where kinetic energy is absorbed into the muscle and tendon as the load is decelerated.

The appeal of eccentric muscle actions is several fold.

Firstly, almost all dynamic movements are preceded by an eccentric muscle action called a counter movement. This sets up a series of physiological events that preloads a muscle, storing kinetic energy to be used in an explosive or dynamic movement.

Some basic physiology!

Secondly, if you are wanting to create a significant muscle and tendon overload to drive adaptations in hypertrophy, power and maximal force expression (maximal strength) then eccentrics tick all of those boxes.

From a muscle and tendon mass perspective it has been shown to create an optimal anabolic environment for muscle growth. Therefore, by definition, this also applies to tendon growth because tendon is an extension of muscle. So the high adaptational stress applied to muscle must also be applied to tendon as well.

The hormonal response to eccentric exercise is significant and has been shown to stimulate insulin like growth factors (IGF) and mechano- growth factors (These are some of the hormones responsible for tissue growth) …. Which should ring a bell or two!

This is because a key physiological process which we understand to be responsible for muscle, tendon and connective tissue adaptations and therefore why we exist as physiotherapists and physical therapists is the process of MECHANOTRANSDUCTION! This is the process by which we think tissues undergo adaptive structural changes in response to mechanical load.

But what else!

Well eccentric exercise it may surprise you to know is pound for pound able to produce more force than other exercise modalities. Now, don’t forget we just spoke about the role of force production in relation to mechanical transduction and how it signals our tissue to adapt structurally. Well eccentric exercise has been shown time and time again to produce between 20 – 60 % more muscle tension than concentric or isometric muscle actions.

And there is more!

For example all explosive movements …. Like throwing a cricket ball, hitting a tennis ball with a racket or hitting a nail with a hammer all have one thing in common!

They all require the preloading of muscle and the use of stored kinetic energy for efficient force production.

The physiological mechanisms that allow this to occur is the stretch reflex and the stretch shortening cycle. Both are important components of dynamic movement something we often wish to improve in our rehabilitation programmes. So, let’s provide you with a basic primer of the physiology!

The stretch reflex is composed of two proprioceptive nerve signals:

1. The muscle spindles

2. The Golgi tendon organs (GTO)

Muscle spindles

The muscle spindles are responsible for providing information to the central nervous system about the amount of force (stretch) acting on a muscle. As stretch acting on a muscle increases so does the responsiveness of the muscle spindle (A practical example of this is when a tennis players arm is in 90 degrees abduction and external rotation before initiating and overhead shot. The anterior rotator cuff and pectoral muscles are subjected to a strong stretch.) The muscle spindles relay information to the brain telling it how hard the muscle must contract to stop the stretch on the muscle and to return it to its original length.

So, in basic terms the stronger the signal from the spindle the hard the muscle will contract.

Remember, the muscles spindles don’t care whether you are serving a tennis ball or you are hitting a nail. Their only concern is to stop eccentric lengthening or excessive stretching of the muscle.

Golgi tendon organs

The GTOs are located within tendons and tell the brain when muscles need to relax. They measure and report changes in the length of tendon hence their name tendon organs. This part of the stretch reflex unlike the muscle spindles is inhibitory to stop high forces acting on the tendon. Its role is to protect the muscle, tendon and connective tissues from damage at all costs. Basically, it’s the body’s emergency cut off switch!

What does this have to do with eccentric training?

Eccentric training trains the muscle spindles to become more responsive to maximal force production and trains the GTOs to become less responsive and to decrease their inhibitory effect. So, all in all the patient can absorb higher levels of kinetic energy or load to stimulate structural adaptations in musculoskeletal tissues and they can produce more force for functional activities.

Stretch shortening cycle

This is the body’s natural elastic tendency to stretch and thereby store energy. It is responsible for the absorption of kinetic energy within muscle and tendons. When a muscle and tendon are stretched the elastic energy is stored within both structures to be used later during the concentric phase. In short, the more energy a patient can absorb the more energy they can apply dynamically during functional activities.

This is very important clinically because it means that we now have a time efficient method to achieve the following:

1.

We can load chronically degenerate tissue to effect either a change in the tissue (if it’s still mechanically sensitive to load i.e. it still works) or to mechanically overload adjacent tissue cells to structurally adapt. Or to put it another way, we can load the good tissue that’s still healthy hard so it may compensate for the degenerate tissues inability to produce force.

2.

We can provide a degree of specificity for the patient that needs to decelerate loads because of a sporting or occupational need. A typical situation where this in important is the recreational overhead athlete. For example the tennis or cricket player that has symptoms during the follow through phase of the serve.

3.

We can use it early during a rehabilitation programme on the non affect side to drive neurological adaptations on the affected side by means of cross talk. In a patient where it is contraindicated to load the affected side (e.g the first 2-5 weeks after a sugical rotator cuff tendon repair ) it has been shown that high force exercise (eccentric exercise) on the non operated side minimises the loss of muscle strength. This is associated with the maintenance of muscle mass, increase anabolic hormone production and up regulations of growth-related factors to maintain muscle strength and mass on the operated arm.

4.

We also have an alternate method for developing high levels of muscle power and maximal force expression. This relates to the higher net force production created by the physiological process that preloads muscle. This increases the storage of kinetic energy to be used in explosive movements. This is why training the eccentric phase of a movement before the concentric component leads to an increase in the rate force production (i.e. a more explosive movement).

So I hope this has provide you with a basic overview of why eccentric training can be used in a shoulder rehabilitation programme at all stages.

Further reading

Cools, A. M., Borms, D., Castelein, B., Vanderstukken, F., & Johansson, F. R. (2016). Evidence-based rehabilitation of athletes with glenohumeral instability. Knee Surgery, Sports Traumatology, Arthroscopy: Official Journal of the ESSKA, 24(2), 382–389. https://doi.org/10.1007/s00167-015-3940-x

Douglas, J., Pearson, S., Ross, A., & McGuigan, M. (2017). Chronic Adaptations to Eccentric Training: A Systematic Review. Sports Medicine (Auckland, N.Z.), 47(5), 917–941. https://doi.org/10.1007/s40279-016-0628-4

Kibler, W. B., Wilkes, T., & Sciascia, A. (2013). Mechanics and pathomechanics in the overhead athlete. Clinics in Sports Medicine, 32(4), 637–651. https://doi.org/10.1016/j.csm.2013.07.003

Kovacs, M., Roetert, E. P., & Ellenbecker, T. (2008). Efficient Deceleration: The Forgotten Factor in Tennis-Specific Training. Strength & Conditioning Journal, 30, 58–69. https://doi.org/10.1519/SSC.0b013e31818e5fbc

Michener, L. A., Abrams, J. S., Bliven, K. C. H., Falsone, S., Laudner, K. G., McFarland, E. G., Tibone, J. E., Thigpen, C. A., & Uhl, T. L. (2018). National Athletic Trainers’ Association Position Statement: Evaluation, Management, and Outcomes of and Return-to- Play Criteria for Overhead Athletes With Superior Labral Anterior-Posterior Injuries. Journal of Athletic Training, 53(3), 209–229. https://doi.org/10.4085/1062-6050-59-16

Richardson, E., Lewis, J. S., Gibson, J., Morgan, C., Halaki, M., Ginn, K., & Yeowell, G. (2020). Role of the kinetic chain in shoulder rehabilitation: Does incorporating the trunk and lower limb into shoulder exercise regimes influence shoulder muscle recruitment patterns? Systematic review of electromyography studies. BMJ Open Sport & Exercise Medicine, 6(1), e000683. https://doi.org/10.1136/bmjsem-2019-000683

Suchmel, T. J., Wagle, J. P., Douglas, J., Taber, C. B., Harden, M., Haff, G. G., & Stone, M. H. (2019a). Implementing Eccentric Resistance Training-Part 1: A Brief Review of Existing Methods. Journal of Functional Morphology and Kinesiology, 4(2), E38. https://doi.org/10.3390/jfmk4020038

Suchomel, T. J., Wagle, J. P., Douglas, J., Taber, C. B., Harden, M., Haff, G. G., & Stone, M. H. (2019b). Implementing Eccentric Resistance Training—Part 2: Practical Recommendations. Journal of Functional Morphology and Kinesiology, 4(3), 55. https://doi.org/10.3390/jfmk4030055

Vogt, M., & Hoppeler, H. H. (2014). Eccentric exercise: Mechanisms and effects when used as training regime or training adjunct. Journal of Applied Physiology (Bethesda, Md.: 1985), 116(11), 1446–1454. https://doi.org/10.1152/japplphysiol.00146.2013

Wagle, J. P., Taber, C. B., Cunanan, A. J., Bingham, G. E., Carroll, K. M., DeWeese, B. H., Sato, K., & Stone, M. H. (2017). Accentuated Eccentric Loading for Training and Performance: A Review. Sports Medicine (Auckland, N.Z.), 47(12), 2473–2495. https://doi.org/10.1007/s40279-017-0755-6

Watson, S., Allen, B., & Grant, J. A. (2016). A Clinical Review of Return-to-Play Considerations After Anterior Shoulder Dislocation. Sports Health, 8(4), 336–341. https://doi.org/10.1177/1941738116651956

Wilk, K. E., Arrigo, C. A., Hooks, T. R., & Andrews, J. R. (2016). Rehabilitation of the Overhead Throwing Athlete: There Is More to It Than Just External Rotation/Internal Rotation Strengthening. PM & R: The Journal of Injury, Function, and Rehabilitation, 8(3 Suppl), S78-90. https://doi.org/10.1016/j.pmrj.2015.12.005

Wilk, K. E., Meister, K., & Andrews, J. R. (2002). Current concepts in the rehabilitation of the overhead throwing athlete. The American Journal of Sports Medicine, 30(1), 136–151. https://doi.org/10.1177/03635465020300011201

Wong, E. K. L., & Ng, G. Y. F. (2009). Strength Profiles of Shoulder Rotators in Healthy Sport Climbers and Nonclimbers. Journal of Athletic Training, 44(5), 527–530. https://doi.org/10.4085/1062-6050-44.5.527