Mobility Explained - Michael Ray, D.C.
Rolling through Instagram or Facebook, we find narratives and interventions claiming to improve something called “mobility”. We can select from options including stretching, foam rolling / body tempering, lacrosse ball smashing, voodoo flossing, power tools converted to guns being sold as therapeutic, and the list goes on. The level of marketing would make even Donald Draper of Mad Men proud.
But are these implements doing what we think they are? Are we just hidden pliable versions of Gumby walking around, waiting for our supple potential to be released? Or, are we committing the post hoc ergo propter hoc fallacy? Before we decide, we must first define our terms and examine the narratives being given to validate these interventions.
So how do we define mobility?
In the research world and hospital setting, the word “mobility” is simply defined as the ability to move.1
In contrast, in the fitness and outpatient rehab world we now find the term being used to substantiate all sorts of bizarre narratives for perceived problems, which then require intervention to fix. We especially see the term tossed around when a person’s movement doesn’t meet the observing clinician’s/coach’s standards of perfectionism or idea of “normal”.
Movement has been dichotomized to “good” vs “bad” based on this idea of mobility, as if it is a pathological issue. As a result, it has generated numerous guru systems purported to treat these perceived problems. However, the real problem is clinicians’/coaches’ tendency to become anchored to our subjective view of how we think movement “should” look. This is usually based on our prior experience, and often has little room for the broad range of normal inter-individual variation.
This misuse of the word continues to perpetuate people’s search for magical tools to improve their mobility so that they may obtain the perfect qi of athletic performance. The search often comes at the expense (in terms of time, money, and effort) of more specific sport practice or training. But, we’re getting ahead of ourselves.
How do we assess movement?
We tend to assign non-qualified adjectives to movement. What is a “poor position”? “Poor movement”? We need to qualify such terms. Is it simply less visually appealing compared to what would be viewed as “better” movement? Or is the movement suboptimal for some metric of performance (meaning the person could complete more reps/sets/increased load/resist fatigue/etc.)?
This is also under the assumption that pain is not a variable in the process. But even if pain is a relevant variable: is the movement painful or injurious specifically because of the way it is performed, or is it more of a question of dosage/loading?2 Often, the extremes of biomechanical demands are where we can get into trouble here (like anything in life).
We also need to consider the impact of other contextual factors including fear-avoidance, catastrophizing, conditioning, and/or the narratives previously provided in these situations — in other words, what has this person been told before about pain and injury as they pertain to movement and mechanics?3,4
There certainly exist advantageous positions/movements from which to exert force based on physics and biomechanics – but these movement parameters are also broad and adaptable based on the individual and their prior training experience. Even at the highest levels of sport where maximal movement efficiency can differentiate winner from loser, substantial technical variability is readily apparent between competitors, rather than rigid adherence to an idealized movement “model” that might be predicted by physics alone.
Consider that spinal flexion in the deadlift, elbow flare in the bench press, or knee valgus in the squat, for example do not universally, automatically produce acute injury. Yet, when pain or injury does occur, athletes are quick to point to these often minor mechanical deviations as the singular cause of their symptoms, often because they have been told these things should be avoided at all costs.
Yet, we have data on inter-individual differences in preferred lifting techniques. Let’s use the example of spinal kinematics during lifting an object from the ground (deadlift).
Pavlova recently completed a study examining the curviness of participant’s lumbar spine and its effect on lifting an object from the ground during three different trials.5 The first trial the participant lifted “freestyle”, no cueing. The second trial the participants were cued to squat (“keep the back straight and bend at the knees”), and finally the third trial to stoop (“keep the legs straight and bend at the back”). The authors’ findings:
“In this study we have shown that the curviness of the lumbar spine is associated with the way in which individuals lift a weight from the floor. When no instruction was given, individuals with more lordotic lumbar spines preferred to stoop down to pick up the box, while those with straighter spines preferred to squat. Our results also suggest that these natural movement preferences are maintained when instructions are given, especially in individuals with curvier spines who prefer to lift by stooping. In changing between lifting styles, individuals adjusted their knee flexion while maintaining their preferred lumbar flexion range.”
These findings certainly question the forced constraint or “one size fits all mentality” rather than allowing for variability and a degree of subjective preference when completing a task.
The authors go on to conclude:
“These results could be important for a reassessment of lifting guidelines, one size does not fit all, and for training of athletes where a given task may place different demands on different athletes depending on their natural lifting technique, which may depend on the shape of their lumbar spine.”
Interestingly, it is often the coaches/clinicians working with athletes who drive this idea of perfectionism, defined as “… a personality disposition characterised by striving for flawlessness and setting exceedingly high standards of performance accompanied by tendencies for overly critical evaluations of one’s behavior.”6
Unfortunately, perfectionism tends to be counterproductive for progress. We now have emerging data suggesting that such an approach can contribute to injury risk (See Perfectionism predicts injury in junior athletes: Preliminary evidence from a prospective study).6
So we tend to have an ideal in our minds of what movement should or shouldn’t look like. We become Procustean arbiters of movement. The current evidence contradicts the purported benefits of aggressively reducing variability in movement, but instead suggests quite the opposite. Variability appears to enhance motor learning and provides the nervous system alternative pathways to complete a movement rather than “solidifying” or, better put, restricting it into set constructs of operation.
Here is an applicable article: Temporal structure of motor variability is dynamically regulated and predicts motor learning ability by Wu et al.7
The initial question many researchers like Wu set out to answer: is the initial high variability of a new movement pattern an obstaclethat impedes effective performance, or is it facilitating the motor system’s ability to learn?
Wu went on to demonstrate that movement variability promotes motor learning. His experiment studied subjects engaging in hand-trajectory motor learning tasks and tracking variability structure as a predictor of the rate of learning. Studied participants were tasked with tracing shapes in four separate experiments.
The authors’ guiding principle was Reinforcement Learning Theory, which basically states that learning occurs via interaction with one’s environment through trial and error. Motor learning occurs by the consequences of one’s actions; in essence, exploitation of past experiences and exploration of new ones.
Participants received no error-based feedback and their behavior was only rewarded based on performance (tracked on a scale of 0 – 1000 based on similarity of shape traced), similar to a coach praising an athlete for completing a movement within the confines they deem acceptable.
Overall the authors found:
“Remarkably, we found that individuals with higher task-relevant variability at baseline learned faster than those with lower baseline variability and that tasks associated with higher baseline variability in task-relevant dimensions elicited faster learning. Interestingly, we found that neither the inter-individual nor the inter-task effects of variability were specific to reward-based learning, as we also observed them in an error-based force-field adaptation paradigm. Taken together these results suggest a general principle whereby increased variability enables faster learning.”
If anything, this study tells us that a person with more total variability when learning a movement will achieve the desired outcome (task) faster than others with forced movement constriction. Even more intriguing, variability likely provides alternative avenues of completing a movement via the exploitation aspect of motor learning.
Dhawale did a recent review and came to similar conclusions as Wu:
“Although noise in nervous system function can often be detrimental to optimal performance, the studies we have reviewed here suggest that neural variability may also be conducive to motor learning, in line with reinforcement learning theory. Random fluctuations (or noise) in the activity of neurons could plausibly underlie such motor exploration, but recent findings suggest that the nervous system is more deliberate and sophisticated than that and may be regulating and shaping motor variability actively to augment learning.”8
So why do we get attached to these implements to improve this ill-defined term, mobility?
The instant gratification of things…..
Anything worth doing takes time and effort. Many of the “mobility implements” mentioned above may provide instant gratification from a temporary increase in range of motion, decreased perception of soreness, and/or decreased “tightness” (another nebulous term). However, this doesn’t mean the person can automatically utilize the new-found range of motion, that it meaningfully translates to performance, or that it provides any net positive impact over the long term.
More importantly, are we just wasting time while perpetuating false narratives? We should view this discussion through a lens of maximizing return on investment (ROI), which can be defined as:
ROI = (Gain from Investment – Cost of Investment) / Cost of Investment
In our case, much of the data is qualitative. Our “Cost of Investment” is time, effort, and depending on the implement in question, money. Our potential gain would be based on the supplied narrative. The question then becomes: did the gains outweigh our cost? Our primary argument in the case of these implements is no.
With this in mind, we don’t want to oversimplify the investment of time, a commodity we can’t manufacture or get back once spent. So, if we are going to condition people to narratives and implements, we should have strong supporting evidence. Now, let’s break this idea down a bit more for each technique.
So what is stretching, exactly? There are three variations of stretching typically described in the literature.
Static: place the muscle in a lengthened position and hold this position; often held at an uncomfortable but tolerable end range of motion between 10 and 30 seconds.9
Dynamic: utilizes active muscle contraction and momentum to lengthen muscle without holding the end-range position.9 [As an aside, I take issue with dynamic stretching being categorized under the umbrella of “stretching” because it’s simply unloaded movement. Example: performing air squats prior to doing back squats (we will get to performance effect shortly)]
Proprioceptive Neuromuscular Facilitation (PNF): there are 2 types typically utilized (there are different derivations to these two types and some contention on the definition of PNF), “contract-relax” (CR) and “contract-relax, agonist contract” (CRAC).10
CR: muscle being targeted is brought to end-range where resistance is felt. The person being stretched then actively contracts against resistance (isometrically), and then the targeted muscle is taken into a new position of limitation.
CRAC: same as CR but instead of targeted muscle being contracted, the opposite muscle group is contracted against resistance. Then, the targeted muscle is taken into a new position of limitation.
The usual narratives surrounding the validation of stretching are as follows:
Clinically: helps with contractures
Make “tight” muscles “loose”
Decrease delayed-onset muscle soreness (DOMS)
Increase overall range of motion
Decrease injury risk (notice this does not say prevent – we can’t prevent anything in regards to athletic based injuries, but we can appropriately hedge our bets to reduce risk). For a more in-depth discussion, see Bahr 2016).11
The overall cost for stretching would be time, effort, and potentially money if we are paying a clinician/coach to complete the intervention passively.
Beginning with contractures allows us to consider complicated medical situations in which ROM is likely clinically reduced and stretching may appear warranted.
Contracture is a shortening and stiffening of muscles that limits joint range of motion, and typically occurs in patients after stroke, brain/spinal cord injury, cerebral palsy, and in other neurological conditions. They can also occur in certain non-neurological musculoskeletal issues such as rheumatoid arthritis, burns, and post-op situations.
The latest Cochrane review on the topic doesn’t show much supporting evidence for the use of stretching to prevent or treat contractures:
“There was high‐quality evidence that stretch did not have clinically important effects on joint mobility in people with or without neurological conditions if performed for less than seven months.”12
If seven months seems odd as a cutoff point, it’s because none of the included studies examined the topic longer than 7 months … so perhaps the 8 month mark is when the magic happens, but it’s doubtful.
Regarding “tight” muscles and range of motion: stretching is consistently demonstrated to alter perception (i.e., “feeling tight”) or tolerance to a position, but not actually altering tissue structure in a meaningful way. The most recent review by Freitas,Can chronic stretching change the muscle-tendon mechanical properties? A review, found:
“Stretching interventions with 3- to 8-week duration do not seem to change either the muscle or the tendon properties, although it increases the extensibility and tolerance to a greater tensile force. Adaptations to chronic stretching protocols shorter than 8 weeks seem to mostly occur at a sensory level.”13
Delayed onset muscle soreness (DOMS):
DOMS is interesting and warrants its own future article to sufficiently discuss the nuanced aspects of the topic. With that said, DOMS can be objectively measured (though the validity of these measures is worthy of discussion) but is a subjective experience similar to pain perception. DOMS is something we may perceive post-exercise, and we can alter perception with all sorts of implements. The question becomes: how do we maximize our time with greatest return on investment for improving performance at specific tasks? Over the long term, if an athlete is continuously experiencing DOMS, then we should be assessing relevant performance and recovery variables with research support: training loads & programming variables, sleep, and nutrition. However, competitive athletic events pose scenarios where many are seeking short term gains (feeling of decreased DOMS and improved recovery and fatigue levels). This is a discussion for a later time, but the research on stretching isn’t supportive for improving DOMS.
More to the point; even if you may feel like stretching alters DOMS – the evidence shows otherwise. According to a Cochrane review, Stretching to prevent or reduce muscle soreness after exercise:
“The evidence from randomised studies suggests that muscle stretching, whether conducted before, after, or before and after exercise, does not produce clinically important reductions in delayed‐onset muscle soreness in healthy adults.”14
A recent review by Peck covers this topic well. “Performance” is a broad term and needs to be qualified to examine relevant research.15
Peck classifies sport performance into 3 categories:
Strength and Power Dominant: “brief and maximal effort” activities (countermovement jump for max height or 1RM in resistance training)
Speed and Agility Dominant: “cyclical, short-duration, fast muscular contraction events” (100 m sprint or less and/or repeated, quick, and multidirectional movements).
Endurance Dominant: “cyclical, longer-duration” activities (running for 200 m or longer, cycling, or submax muscular endurance repetitions for resistance exercises).
For static stretching the following conclusions were drawn from the evidence:
Strength and Power: Performing static stretching by itself immediately before strength and power activities diminishes performance. If static stretching is performed with sufficient time prior to activity (articles proposes 15 minutes) or is subsequently combined with other types of warm-up, then no effect occurs on strength and power activities. Basically, either no effect or detrimental effect … leading to the conclusion that it is not worth our investment.
Speed and Agility – When performed prior to speed and agility activity, static stretching is detrimental to performance. Similarly with strength and power, if a dynamic stretch or general warm-up is completed after static stretching then the detrimental effect may be reversed, but this does not imply an improvement in performance but rather a return to baseline (zero). Peck does go on to say that static stretching may affect speed and agility performance differently based on baseline characteristics of the athlete’s level of flexibility.
Endurance: Based on the current available literature, Peck states,
“It is unclear whether static stretching impairs either longer-duration (200 m or greater) cyclic activity or submaximal muscular endurance, but it is notable that no study shows a performance benefit from static stretching performed prior to these activities.”15
Which means, either no benefit or potentially negative effect.
Now, on to effects of dynamic stretching. To reiterate, dynamic stretching appears to be a misnomer because it describes active unloaded movement, rather than holding a particular position at end range statically. For argument’s sake, dynamic stretching will be discussed as unloaded movement for the remainder of this article. With that said, there does appear to be some nuance to the discussion of unloaded movement prior to sport performance.
Strength and Power: Improves performance for strength and power dominant activities, but we aren’t sure how it stacks up to just doing lower intensity externally loaded movements or combination of both unloaded and loaded movements. Peck concludes:
“It appears from the preponderance of evidence that dynamic stretching improves strength and power performance when performed immediately prior to the event. Whether a combination of dynamic stretching and heavy-load exercises prior to an activity such as the countermovement jump further improves performance is unclear.”15
Speed and Agility: Yes, unloaded movements do appear to be beneficial prior to the performance of speed and agility movements. Which, of course, are also typically unloaded movements. Peck cautions, “However, excessive volume may induce fatigue and affect speed and agility performance adversely.” In other words, don’t drain the energy account too quickly, or you might find yourself in the red and owing an NSF.
Endurance: Not enough evidence either way. Probably best to not make bets when we have no evidence for defining our risk.
Regarding PNF, we need more evidence, but it’s not looking good – particularly for strength and power activities.
Decreased Injury Risk:
A 2014 study by Lauersen et al, “The effectiveness of exercise interventions to prevent sports injuries: a systematic review and meta-analysis of randomised controlled trials,” found:
“Stretching did not show any protective effect (RR=0.961 (0.836–1.106)), while strength training proved highly significant (RR 0.315 (0.207–0.480)).”16
Imagine that: stretching didn’t affect relative risk for injury, but strength training had a significant protective effect. This would seem to further support the loaded movement argument.
The moral of the investment story here: stretching offers little to no benefit in relation to our required investment of time, effort, and potentially money. We will be discussing other implements such as foam rolling, body-tempering, voodoo flossing, etc in future articles. In the meantime, it is important to:
Arm yourselves against silly BS.
There are a few easy ways to make money in the rehab/fitness world.
Use vague statements about a perceived problem (e.g., mobility) to sell a product.
Increase buy-in with the following:
Utilize testimonials (preferably pro-athletic teams or well-known athletes for the sports rehab world)
Develop dependency via fear-mongering (if you don’t do this ONE thing, or use “X” tool every day for “X” minutes a day then you will be in pain or your performance will suffer – and your success in the gym/sport depends on this!)
Amass as many followers as possible (charismatic personality helps and giving away free stuff – it also doesn’t hurt to hire attractive people … welcome to marketing).
Stir controversy to obtain increased attention
Consistently pump out new products to solve new perceived problems or invent new problems while developing products to solve them.
Repeat process indefinitely
Don’t forget that past products are able to be rebranded/repackaged to solve forgotten perceived problems.
A few of these points are worth touching on.
We have enough evidence at this point that, as clinicians/coaches, our words matter and affect all sorts of things such as beliefs, expectation, conditioned behaviors, and ultimate treatment outcomes, to name a few.
The narratives surrounding these implements drive beliefs and conditioned behaviors, increasing unnecessary reliance on the part of the users, while the creators and proponents are profiting.
Athletes and patients may find themselves spending hours a week “rolling out” non-existent adhesions or myofascial trigger points (discussed HERE).
Or stretching, because somewhere along the journey some well-meaning person suggested that an individual has a “bad” squat or is experiencing low back pain because they have “tight” hamstrings or psoas muscles. We lack supporting evidence for either of those narratives.17 But we do have evidence showing how the words utilized for these narratives can make matters worse for patients.18,19,20, 21 As clinicians/coaches, our narratives have the potential to build resiliency or instill vulnerability.22
These narratives then get cemented in the person’s mind, leaving them with the idea that they require some implement to “fix” them so they may someday achieve an arbitrary model of movement perfection. In reality, the person probably just needs to spend more time practicing said movement … but this doesn’t get likes on Instagram or Facebook … nor does it sell products.
Imagine a world where everyone has high self-efficacy and doesn’t rely on inappropriate narratives and products to find success, but realizes they have everything they need to be successful … and supple … just imagine.23
The term mobility has been manipulated to sell narratives and products. We likely should change our vernacular to just discuss range of motion. The odds are, we have the necessary range of motion to accomplish our desired activities, but we may be unadapted to accessing the desired range of motion and require more time training the particular movement we wish to improve.
Don’t buy into the silly BS.
Stay tuned for future blogs discussing other implements and the miraculous claims accompanying them.
Special thanks to Drs. Austin Baraki and Derek Miles for their help with this article.