The Role of Specificity in Musculoskeletal Rehabilitation

In recent years the debate about specific vs. general exercise for treating non specific pain seems to have died down somewhat among academics. This may just be my ignorance, but I have not been seeing papers about this subject as much recently. However, this debate still rages on amongst clinicians, implicitly, as is demonstrated by their exercise prescriptions. Unfortunately, as is also demonstrated by their prescriptions, there is a very widespread lack of understanding of the term specificity from an exercise science perspective.

The goal of this article is to clarify in what sense specificity is relevant to rehabilitating chronic pain and also injury. To do this, it makes sense to start with a definition of specificity. In general, specificity can be defined as “The quality or fact of being specific in operation or effect” (1). To make it relevant to physiology, we need to add some specificity. lol. 

Each stimulus (stress) causes an adaptation in the body that is unique to that stimulus (type, magnitude, duration etc.).

In the context of exercise/sport physiology we would say: “… training should tax and stimulate the underlying systems of the sport task.” (2)

This is true whether you are injured, healthy, in pain or pain free. What changes are the goals of the individual and the constraints put on them by their condition and environment. So what are the goals, and what are the constraints?

Let us start with the simpler case; traumatic injury. If we take the case of a torn ligament, and subsequent surgical repair, the goals for rehabilitation are: 

1. Restore ROM of the joint

2. Restore size and strength of the surrounding muscles

3. Restore other qualities (power, motor control, sport skills etc.)

The main constraint is the time it takes for the injured tissue heal. 

I do not think as many clinicians are confused about what to do, at least in theory, in this scenario. Although, recent videos of Neymar’s ‘rehab’ might call this into question.

Update; between the time of writing this article and publishing it, Neymar was injured again in his FIRST GAME back.

The rehabilitation of this injury would involve, at first primarily progressive ROM exercises moving into more of a focus on strength and hypertrophy exercises, followed again in a graduated way by introduction to, and focus on speed and/or power exercises. Pretty simple. 

The exercise choices at first will not matter much because there are very few ways to stretch a particular muscle, or move a joint through its ROM without load. In other words, they will all be specific. The exercises later in the rehabilitation program should be increasing in specificity over time to prepare for the tasks that the individual needs to perform, thereby increasing their performance of those tasks. This is literally the entire point of rehabilitation (and training).

It is honestly amazing that the last point isn’t completely obvious in all cases, but again, it seems to be more clear or well-defined in a post-surgical scenario. I think it is the scenario below that causes more uncertainty, which results in much fuckery. Unfortunately the ones who need to hear it will probably not find this, but here is a definition of rehabilitation just in case:

“Restoration of a person to health or normal activity after injury…”(1)

In the case of chronic and/or non-specific pain, there is (by definition, in non-specific) not always a clear pathoanatomical diagnosis, and there is often no mechanism of injury. So, what are the goals and what are the constraints?

Depending on which three letter acronymized organization the clinician prays to, you will get very different answers. Fixing asymmetries, increasing ‘strength’, improving ‘mobility’, increasing ‘stability’ are just a few possibilities. The words in quotes are as such because they are often used inappropriately in my experience. You may notice that if these are the goals put forth by the clinician, they may have already gone off track. The goals and justifications for various manual therapies are even more inappropriate to the point of being absurd, and will be discussed elsewhere.

From my perspective, the goals are obvious, at least at a high level: Get rid of pain (mostly), return to previous level of function (or higher), and possibly decrease the likelihood of pain returning. The constraints may be more difficult to identify, and are very much dependent on the individual. Some common examples are comorbidities, occupational stress etc. You will notice that these constraints could also apply to the previous scenario, but the more important factor there is just healing time.

So how do we achieve pain relief with exercise? Before attempting to answer that question, we need to make a distinction between uses of the term ‘specific’. In the research on exercise and MSK pain, the term ‘specific exercise’ means roughly region specific exercise. To put it another way, exercising the painful area, typically with resistance exercises. 

To date, the literature on region specific exercises compared to general exercise for spinal disorders and knee OA have failed to demonstrate a meaningful benefit to region specific exercise. (3) A large systematic review comparing general exercise to specific exercise for chronic neck and shoulder pain found mostly no difference (slightly favoring specific) between the two for short and long term outcomes. The authors of this study remarked: “Therefore, the type of exercise might be less important than the act of doing exercise.” They go on to state another very stimulating point: “The reason that the research to date has not shown any specific exercise to be superior may be that psychological and/or neurophysiological factors that are common to all exercise approaches have the greatest mediating effects on pain.” (4)

Some research shows that the generalized analgesic (pain relieving) effect of exercise is actually neutralized by exercising a painful muscle and may even cause hyperalgesia (increased pain/sensitivity) in certain populations. (5) So it would seem that based on the current body of evidence, region specific exercise is at least not necessary to achieve pain relief in chronic pain populations.

So if it doesn’t matter which exercises we do, which ones should we do?

Again, it seems entirely obvious to me to choose the ones that are most likely to help the patient achieve their functional goals. That is, specific exercises (exercise physiology definition). If they lead to a significant increase in symptoms, modify them as much as necessary to allow improvement. This does not have to be at the complete omission of things that are less specific to a goal, but their money and time in the clinic should not be wasted doing circus tricks that require a heroic stretch of the imagination to even be called exercise.

Let us put it this way; the patient has functional goals, and for the purposes of pain relief it may not matter which exercises we do. So do ones that will help the patient achieve their functional goals. 

If their goal is to be able to blow up a balloon while laying on their back with a ball between their legs, then do PRI exercises. Otherwise do proper exercise. If the patient needs to lift and carry heavy things at work, give them a progression involving heavy lifting and carrying exercises. If they need to jump higher for their sport, give them a progression of power and plyometrics exercises. Glute bridges and dead bugs for every person with lower back, hip or knee pain simply does not cut it anymore.

It should go without saying, though again my experience suggests it absolutely does not, that all of these decisions should be made after a thorough evaluation of the patient considering all relevant physiological, psychological and sociological factors involved.

References

1. Oxford University Press. (n.d.). Rehabilitation. In Oxford English Dictionary. Retrieved September 20, 2024, from https://www.oed.com/search/dictionary/?scope=Entries&q=rehabilitation.

2. Israetel, M., Smith, C. W., & Hoffman, J. (2015). Scientific principles of strength training. Juggernaut Training Systems.

3. Ouellet P, Lafrance S, Pizzi A, Roy JS, Lewis J, Christiansen DH, Dubois B, Langevin P, Desmeules F. Region-specific Exercises vs General Exercises in the Management of Spinal and Peripheral Musculoskeletal Disorders: A Systematic Review With Meta-analyses of Randomized Controlled Trials. Arch Phys Med Rehabil. 2021 Nov;102(11):2201-2218. doi: 10.1016/j.apmr.2021.01.093. Epub 2021 Mar 6. PMID: 33684362.

4. Dueñas L, Aguilar-Rodríguez M, Voogt L, Lluch E, Struyf F, Mertens MGCAM, Meulemeester K, Meeus M. Specific versus Non-Specific Exercises for Chronic Neck or Shoulder Pain: A Systematic Review. J Clin Med. 2021 Dec 18;10(24):5946. doi: 10.3390/jcm10245946. PMID: 34945241; PMCID: PMC8706212.

5. Nijs, J., Kosek, E., Van Oosterwijck, J., & Meeus, M. (2012). Dysfunctional endogenous analgesia during exercise in patients with chronic pain: To exercise or not to exercise? Pain Physician, 15(3 Suppl), E205–E213. PMID: 22786458.