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by Jenni Rawlings & Travis Pollen, PhD

In the yoga world, there is a growing dialogue about the difference between one’s active and passive ranges of motion. Improving active range of motion is said to be important for preventing injuries, and end-range training methods are often taught with this goal in mind. Movement “prerequisites” concerning active range of motion have also grown more common due to the belief that increasing this type of end-range control reduces injuries. Today we’ll examine this trend and explain why improving our active range of motion is certainly beneficial, but claims about injury prevention are premature and potentially counterproductive.

For those new to these terms, active range of motion (aROM) is the range of motion of a joint that one’s neuromuscular system can control through active force production, while passive range of motion (pROM) is the range of motion that a joint can be moved through passively.

For example, consider the classic yoga pose utthita hasta padangusthasana (standing big toe pose), where we balance on one leg and hold the other leg out in front of us, hooking the big toe with the fingers of the same-side hand. When we hold our leg in front of us at its end range of hip flexion with our arm, we are displaying our pROM because that leg is relatively relaxed (passive) and our arm is doing the work to hold the leg up. However, if we release our clasp of the big toe and attempt to keep the leg high in the air, we will shift into our aROM because the muscles of the leg are now actively working to hold the leg up.

It’s almost always the case that we can move a joint farther using our pROM than we can using our aROM. In the aforementioned big toe pose example, there will generally be at least a slight drop in height of the leg if the yogi releases the big toe but continues to hover their leg in the air, effectively switching from pROM to aROM.

This difference in range between one’s aROM and pROM is often referred to as a “gap.” A common claim to hear in the yoga world these days is that the larger one’s gap between aROM and pROM, the more prone to injury that particular joint is – or another joint somewhere down the kinetic chain is (as a result of a compensatory movement). Therefore, “closing the gap” by expanding aROM is said to be an important means of injury prevention. (Sometimes the claim is even made that our aROM & pROM should ideally match and there should be no gap between them at all, which actually isn’t physiologically possible.)

To further our understanding of the aROM/pROM “gap,” a brief primer on the length-tension relationship would be helpful. The length-tension relationship describes how a muscle’s strength (or ability to produce active force or “tension”) changes depending on that muscle’s current length. It turns out that muscles are strongest at their resting length (mid-range length). But when a muscle is in either a lengthened or shortened position, it has less ability to actively produce force. The gap between aROM and pROM is a natural consequence of this relationship. The length-tension relationship of muscle can be represented visually by a curve, as seen in this graph:

The horizontal x-axis represents muscle length and the vertical y-axis represents tension/force production. As you can see, when a muscle is at its mid-range, it has the highest amount of active force generation available to it (the peak of the curve), and as the muscle becomes shorter or longer (moving left and right along the x-axis), the amount of force it’s able to generate decreases.

End-range training begins with moving a joint towards its passive end range of motion. In this end range, the tissues that cross that joint are lengthened on one side and shortened on the other – both positions in which the muscle is less strong. One of the most commonly employed techniques is to then perform muscle contractions of both the lengthened and shortened muscles.

As we’ll see, it’s tempting to believe that this type of strength work by itself can reduce injuries, but the reasoning behind this argument is questionable and as yet untested in the current evidence on injury prevention.

Why End-Range Training is a Good Method to Use

Before we go any further, we want to make sure to state that we are personally fans of end-range training. In fact, we practice and teach these methods ourselves! Here are some solid reasons that end-range training can be beneficial:

• It can improve flexibility faster than passive stretching alone (acutely).

• It can increase muscle strength and size.

• It can improve our proprioception (our nervous system’s sense of our body in space).

• It can increase the number of contractile units within our muscles (sarcomeres), giving our nervous system more tissue to communicate with for movement.

• It can improve our ability to do cool and impressive movement feats such as those that receive lots of “likes” on social media.

With all of these great reasons to employ these types of training methods, we don’t need to make questionable claims about other benefits. In particular, we believe our language around injury prevention and end-range training to close the aROM/pROM gap needs a makeover.

Why is “Closing the Gap” Believed to Prevent Injuries?

The rationale for attempting to increase one’s aROM so that it more closely matches pROM is two-fold. First of all, end-range training increases the strength of our tissues (tendons, ligaments, joint capsules, and muscles) in an end-range position. And because many injuries tend to happen in our joints’ end ranges, it seems logical to assume that the more strength we build in our tissues at end range, the less likely they’ll be to injure as a result of loads applied.

Second, we only have neurological control of our joints within their active range. This means that the larger our aROM/pROM gap, the more passive range we have available to us in our end range that we can’t control. Therefore, when presented with a risky, injurious situation, there’s more opportunity for us to enter a range of motion we can’t control and sustain an injury if we have significantly more pROM available in a joint than aROM.

On the surface, this reasoning sounds logical, and it has influenced many trends in the yoga world. We will readily admit that we have found these arguments quite compelling in the past, and we’ve made our fair share of claims about the importance of closing the aROM/pROM gap, as well – both in our teaching and in our writings. But as educators who seek to continually learn about the body and evolve our perspectives accordingly, we have updated our points of view in the past few years and no longer make these claims.

Why is the Reasoning for “Closing the Gap” for Injury Prevention Questionable?

There are a few reasons to question the notion that closing the aROM/pROM gap is paramount for injury prevention. The first is that while many acute, sudden-onset injuries do tend to happen in end ranges, they are generally the result of high forces applied at high velocities – such as an impact, a fall, or some other type of traumatic accident. By contrast, the forces involved in most end-range training practices are lower in magnitude and velocity and are therefore unlikely to be protective against most acute, sudden-onset injuries.

End-range training most commonly involves taking a joint into its end range and performing isometric contractions in that position. Isometric contractions by definition involve no movement and therefore no speed. Although we can work to “ramp up” our contractions to feel quite effortful while we’re doing them, this type of strength work is simply no match for the higher, faster forces involved in acute, sudden-onset injuries.

(Note: advanced end-range training techniques involving ballistic actions have recently been introduced for athletic performance goals that may address the lack of velocity-specific force production. However, these techniques haven’t seemed to permeate into the yoga setting yet – and may be unlikely to be adopted moving forward due to the slower-velocity nature of most yoga practices.)

The strength and neurological control that would really have the potential to prevent acute injuries is the strength and control of a joint before it reaches end range – i.e. more toward its mid-range. As we mentioned, due to the length-tension relationship, our muscles have the most active force production available toward their mid ranges, not their end ranges. So that’s the range in which we’d have the most likelihood of “catching” ourselves in the midst of a potential injurious accident, both from a strength and neurological control perspective.

In other words, suppose we lack strength and control in our mid-range joint angles. No amount of end-range strength will likely be able to stop the momentum that’s already developed in an accident-type situation by our inability to control our movement well before we reach that end-range position.

It’s important to point out here that this type of mid-range strength and control is naturally developed through traditional full-range strength training practices – not targeted end-range training. And whereas there is currently little direct evidence supporting closing the aROM/pROM gap for injury prevention, there is plenty of evidence that traditional full-range strength training does prevent injuries.

(Note: It is plausible that end-range training could reduce the risk of overuse injuries for athletes whose sports require extremely repetitive force production near end range (e.g. swimmers and baseball pitchers). However, this potential benefit requires further investigation. And it probably doesn’t apply in the context of yoga, which generally doesn’t involve high-load, extremely repetitive motions.)

What Constitutes an Excessive Gap Between aROM & pROM?

As we discussed above, it’s perfectly normal and natural for our joints to possess more pROM than aROM. Granted, it’s possible that having an excessively large gap between pROM and aROM could be problematic, and in that specific case working on increasing one’s aROM could potentially help reduce injuries.

But where is the dividing line between an acceptable gap and “excessively large” one? Some experts have suggested a 15° gap as the acceptable threshold. Others suggest a 15 percent difference (i.e. aROM must be 85% of pROM) as a quick-and-dirty heuristic. But is there one standard (either a degree or percentage difference) that applies to all bodies – and to all joints?

As it turns out, there’s little research on what constitutes a typical or excessive gap in pROM and aROM. Moreover, what is typical/excessive likely differs depending on the joint action in question, as well as factors like age and sex. Without this knowledge, claims that the larger one’s gap is, the more susceptible they are to injury are purely conjecture.

(Note: The fact that there is no direct evidence that an aROM/pROM gap increases injury risk is not the same as evidence that it does not increase risk. However, as we’ve stated, unless the gap is excessive, there doesn’t seem to be a plausible mechanism by which this would occur.)

As a corollary, some yogis even claim that passive stretching (as practiced in a typical yoga class) makes us more susceptible to injury by increasing pROM without increasing aROM (effectively “widening the gap” instead of closing it). We acknowledge the possibility that a long-term yoga practice consisting solely of high-frequency, long-duration passive stretching (and no concurrent strength training) could contribute to an excessively large gap between aROM and pROM. However, that would be an extreme scenario that doesn't reflect the way we see yoga most commonly practiced.

It’s worth acknowledging here that proponents of closing the gap for injury prevention often make the point that they don’t actually demonize passive stretching. Many end-range training techniques include a passive stretching component, such as holding a passive stretch for a couple of minutes and then adding in strength work in that stretched position afterward.

However, in that sense the passive stretch is effectively treated as a “necessary evil” that must be done in order to get to what’s “actually” beneficial for the body, which is seen as the strength work that comes afterward. Passive stretching done for its own sake – without associated end-range strength work – is not seen as beneficial because it increases pROM without increasing aROM. It is in this sense that passive stretching is often demonized by proponents of “closing the gap.”

Increasing aROM Does Not Necessarily Transfer Into Better Movement

There’s another assumption built into the “close the gap” model that deserves examination: the claim that increasing our aROM will translate into “better movement” and less “faltering” in our general, daily movements.

This notion seems to make sense on the surface. If we can improve our neurological control of our end ranges by gaining strength in those positions, then we can improve how well we move through our daily life.

However, the workings of our nervous system are extraordinarily complex. Although it might seem intuitive to assume that increased aROM will naturally carry over to better movement in general, this is actually a significant conceptual leap in reasoning.

First of all, the phrase “better movement” is a vague term without a clear definition. Better in what way? How do we determine what makes movement better?

Second of all, the way we move in end-range training practices is quite different from the way we move in our everyday movements. End-range training most commonly consists of isometric contractions (no joint movement) in specific positions during a structured movement practice. End-range training can also involve movements that attempt to isolate one joint and circumduct it through its full aROM.

By contrast, everyday movement is dynamic and integrated – a completely different context from structured isometrics and isolated joint work. Additionally, daily life movements rarely even involve end-range positions. So even if we had a clear definition for what “better movement” was, the principle of specificity suggests that the effects of end-range isometrics and isolation movements wouldn’t carry over all that well into how we move through our everyday lives.

Why Does This Matter - What’s the Harm? aROM & Movement “Prerequisites”

The current trend of focusing on end-range training and aROM has led to a related, but separate issue in the yoga world: a new emphasis on movement “prerequisites” for many of yoga’s commonly-practiced poses.

Many yoga instructors now teach that in order for a yoga student to be “permitted” to practice certain asanas, they must possess the ability to embody the joint angles of these positions actively – even if the pose puts them into that position passively. Students who do not possess this prerequisite aROM are advised not to practice these poses until they have first worked to expand their aROMs to the acceptable degrees.

Let’s look at handstand (adho mukha vrksasana), a pose we commonly see these rules applied to. A handstand requires that the wrists extend to 90°. This means that 90° of passive wrist extension is required to practice this pose safely. If someone does not have that ROM in their wrists but jumped up into handstand anyway, they could be more at risk for injury than someone who has more wrist flexibility. This is because they would be forcing their wrists into a range they don’t possess. Hopefully everyone can agree on this point – it’s an instance in which a movement “prerequisite” clearly and correctly applies.

However, it’s common these days for handstand prerequisite rules to be taken one step further based on aROM/pROM beliefs. These days we often hear that someone isn’t “cleared” to practice handstand unless they possess 90° of active wrist extension.

If someone has 90° of passive wrist extension, but less than that in their active range, they will be advised not to practice handstand for the time being in order to avoid injury, and to instead work on end-range training designed to increase their wrist extension aROM. Once their aROM has reached an acceptable level, they will be approved to practice the pose.

We acknowledge that yoga teachers who put handstand off-limits in this way are simply trying to keep their students safe. Nevertheless, while there are many reasons why working on end-range strength in wrist extension can be a great idea, we don’t believe injury prevention to be a major benefit.

A handstand is a static balance pose that places our body weight on our wrists in extension. Provided that we have the 90° of pROM required for this pose, some factors that we know are relevant for injury prevention include progressive overload, dosage, and recovery. For example, we’d want to make sure we’ve progressively loaded our wrists over time before starting a handstand practice. Table top position, down dog, plank, chaturanga, and crow pose are all good poses to build up capacity in wrist extension that is specific to handstand. In addition, we’d want to monitor proper dosage and recovery of a handstand practice over time. If we do too many handstands too soon and without enough rest in between sessions, we may be more likely to experience an injury.

By contrast, the mechanism for how possessing 90° of wrist extension aROM would prevent injuries in handstand is unclear. It’s not inherently injurious for the wrist joints to be passively taken to 90° of extension if they do possess that range, and as long as these joints have a training history of receiving and handling progressive load, the tissues in this area should have the capacity to handle the loads of this pose.

As you can see, effective injury risk reduction in handstand involves optimizing loads and volume over time – more so than meeting an aROM prerequisite. The same could be said for many of the other aROM “prerequisite” claims made in the yoga world these days. Other increasingly common examples include the wrists in urdhva dhanurasana (wheel pose), shoulders in gomukhasana (“cow-faced pose” shoulder opener), the hip in pigeon pose, and more.

Passive range of motion requirements make sense for our yoga poses. If our joints can’t move into the position in question passively, then forcing our joints into the pose is more likely to be injurious. (This is obvious!) But active range of motion requirements generally do not need to be used to assess someone’s readiness to practice a pose (aside from instances of an extremely wide gap, as mentioned earlier).

(Note: If a yogi complains of wrist pain during wrist extension, then we would want to temporarily modify or avoid aggravating poses. In addition, end-range training in wrist extension could be helpful in that situation. But that is a different scenario from preemptively putting handstand off-limits for people who aren’t currently in pain.)

Discouraging Language and Nocebos

Another issue with aROM prerequisites for movements in yoga is that the language used around these rules often has a hint of shaming attached, which can be discouraging and counterproductive. People are regularly told that they haven’t “earned the right” to practice a pose, for example, or that they “don’t own the range” to practice the pose.

Another concerning phrase that is regularly tossed around during aROM conversations is “Prep yourself before you wreck yourself.” This phrase is often used to imply that if people practice poses they haven’t “earned” with dedicated aROM prep work, they will injure (or “wreck”) their joints in these poses. The phrase rhymes and therefore rolls off the tongue easily, but it’s an example of a nocebo: a negative expectation of an otherwise harmless event or action that can cause negative consequences like pain.

Now as mentioned before, if someone lacks the passive ROM to embody a pose, they should certainly steer clear of that pose until they develop the requisite pROM. But this is common sense and doesn’t require a nocebo of a catchphrase to explain to people. No one thinks that their wrists will be safe in handstand if they can only be extended 65° passively, but the pose requires 90°. On the other hand, if someone can passively extend their wrists to 90° but to only 80° actively, this should not disqualify them from practicing the pose. Injury is mediated by many factors, and increased strength and control in handstand will be built by simply practicing handstand.

(Note: certain aROMs may be “prerequisites” for achieving a particular shape, but that’s a different context/conversation from injury risk. For example, to achieve a straight line in handstand, you need full shoulder overhead aROM. However, if you lack some of that aROM, you’re still probably not more likely to injure your shoulder practicing handstand. You simply won’t achieve that straight line shape.)

In summary, aside from being unnecessary, aROM prerequisites for poses (and phrases like “prep yourself before you wreck yourself”) are likely to discourage people, decrease their confidence in the resilience of their body, and reinforce fragilistic beliefs. Practicing a handstand can be an empowering activity that makes movement fun. When we take this pose and others away from people unnecessarily, we are potentially denying them the opportunity to have positive experiences in their own bodies.

Injury Prediction & Prevention are Complex Endeavors

An injury is a multifactorial event with a wide variety of possible contributors ranging from internal risk factors (inside the body) to external risk factors (outside the body). Some risk factors for injury that are often discussed in scientific research include having a previous injury, age, body composition, skill level, anatomical factors, training environment, sports/activity equipment, coaching/teaching factors, psychological factors, and more. The body of scientific literature on these topics is extensive, with important new research in these areas constantly emerging.

All of that is to say that injury prediction and prevention are very complex endeavors. Rules like “close the aROM/pROM gap to prevent injuries” oversimplify how injuries happen and may give the impression that predicting and preventing an injury can come down to a single ratio of joint angles.

It’s interesting to note that despite the vast number of risk factors that can potentially predispose someone to an injury, in the yoga world we often set our focus on just one potential cause and treat it as the most important factor above all other factors. For years in the yoga world, “alignment” was that one factor. “Good alignment” supposedly prevented injuries and “bad alignment” caused them. And today the trend is to treat range of motion as the main factor that matters for injuries. If our aROM and pROM ranges are close to matching, we are believed to be protected against injuries. But if our pROM is larger than our aROM, then we are believed to be vulnerable to injury.

Even if gaps between pROM and aROM do play a role in injury risk (which we question except in extreme cases), pulling out one perceived risk factor like this and emphasizing it above all others is an unhelpful approach because injuries are multifactorial. For example, lack of sleep could be one (of many!) potential risk factors for injury as well, but do we ask people how much they slept the previous night before deciding whether they are “cleared” to work on their handstand? Probably not (but maybe we should)!

In Conclusion

While commonly used end-range training practices have many benefits, claims about injury prevention are reaching beyond the current knowledge base we have about this topic. While innovators and popularizers of such methods may not have intended them to be used in isolation for injury prevention (but rather as one part of a comprehensive training system), this is in large part how they have been interpreted and adopted in their widespread use in the yoga world.

Based on what we know of the high forces and velocities involved in acute, sudden-onset injuries, it’s unlikely that typical end-range training techniques will be protective against such forces. Mid-range strength is likely the more important attribute when it comes to “catching” oneself before an injury occurs in end range. Again, the current literature supports full-ROM strength training for injury prevention. We also have yet to systematically verify that increasing control through end-range isometric strength work carries over into better movement and less faltering in the dynamic movement situations of everyday life and/or sport (which often don’t even require movements near end range).

This a key realization for the yoga community. While many yogis are now understanding the benefits that a strengthening practice can offer them, strength work is commonly being integrated into yoga as end-range training only. Granted, the ideal balance of full-ROM and end-range training will vary from one person to the next based on their current abilities, goals, and injury history. But from an injury prevention standpoint, we recommend yogis emphasize full-range strength training. If you find value in end-range training, sprinkle that on as “dessert” – after your full-range training “main course.”

Additionally, with regard to movement prerequisites in yoga, the use of aROM/pROM gaps to determine whether a yoga student “owns the range” to practice a pose is discouraging and likely unnecessary. Yoga students should possess the passive range of motion required to practice a pose in order to minimize injury risk. A gap between aROM and pROM is normal; as long as it isn’t excessive, it’s not cause for concern. Beyond that, injury risk should be mitigated through other factors, such as progressive overload, dosage, and recovery.

We hope this article will foster productive dialogue around these topics. We certainly don’t mean for it to be a criticism of those who champion the techniques described herein. The science on range of motion is limited, and it's reasonable for scientifically-minded people to come to different conclusions based on the limitations of the existing research and their own experiences as practitioners. That said, the less we take reductionist approaches to injuries in the yoga world, the more we can empower and support our students in their practices.

Related: Yoga Meets Movement Science podcast episode: Stretching Myths & Stretching Facts w/ Greg Lehman

About the Co-Author

Travis Pollen is an author, personal trainer, and PhD in Health & Rehabilitation Sciences. His research focuses on core stability, movement screening, training load, and injury risk appraisal. He also holds a master’s degree in Biomechanics and Movement Science along with an American record in Paralympic swimming. He’s been a yoga student for 15 years. Website | Instagram | Facebook

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