Short Version

Though the term mobility is frequently thrown around in casual conversation, there is not always a true understanding of what it means. The word flexibility is often incorrectly used interchangeably with mobility. Flexibility describes a joint’s capacity to move passively through a range of motion, whereas mobility is a word used to describe a joint’s capacity to actively move through a range of motion. Through researching the subject it seems that the benefits of flexibility training can, in most cases, be achieved through mobility training, but that it is not necessarily the case the other way around.

Long Version

A joint is a part of the human body where two bones meet. That is in simple terms, but there is a lot more complexity to that part of our anatomy. There are 3 different overarching classifications for joints: fibrous (mostly immovable), cartilaginous (slightly or not movable), and synovial (movable) (Juneja, Munjal, Hubbard 2021). So when discussing mobility or flexibility, we are primarily referring to synovial joints which can be broken down into further sub-categories. One example is a ball and socket joint which occurs when two types of bones meet: one with a spherical shaped ending (ball) and the other with a cavity (socket) (Juneja, Munjal, Hubbard 2021). This type of joint allows for backwards, forewards, sideways, as well as rotational movements, and the two examples of this in the human body are the hips and shoulders (Johns Hopkins Medicine). Other joint types allow for different movements, so when figuring out how to manage our joint health it is important to understand their respective capacities so we know how to safely train them.

In the fitness industry there is a clear confusion between the terms mobility and flexibility. Both are associated with joint health, but they result from different methods of training and have different impacts on the human body. Mobility is an expression of active range of motion (ROM) whereas flexibility is an expression of passive ROM. In this instance, active means the utilization of muscles to primarily initiate joint motion, and passive means the motion occurs due to an external force acting upon the joint.

Here is an example to highlight the difference:

Flexibility

1. Hold out your right hand with your palm facing away from your body

2. Place your left hand over your right hand

3. Slowly pull your right hand towards your forearm

4. Go as far back as is comfortable

You just expressed flexibility; you created a passive motion with your joint. The movement of your joint was not initiated by muscles surrounding your right wrist, rather it was initiated by your other hand.

Mobility

1. Hold out your right hand with your palm facing away from your body

2. Keep your other hand by your side

3. Try to bring your hand to the same position as before

You just expressed mobility; you actively moved through a range of motion. The movement was initiated by the activation of the muscles surrounding your wrist joint, not another object.

Unfortunately, most of our body functions on the principle of “Use it or lose it” (Hart & Zernicke 2020). If we do not use our muscles, joints, ligaments, or tendons our capacity to use them decreases; they become worse at their jobs. Even bones weaken if they are not used (Minaire 1989). If we were put in a full arm cast due to an injury, we would be unable to use our arm muscles, which would lead to atrophy (degeneration/weakening). “Exercise is intrinsic to who we are… (it) is essential to maintain and sustain integrated optimal functioning” (Hart & Zernicke 2020). Our bodies’ require movement to not degenerate, and they require movement to thrive. If joints are responsible for our movement capacity then taking care of our joints is clearly a key factor in our ability to thrive. So is training active ROM (mobility) or passive ROM (flexibility) better?

That question is complex because there are a variety of benefits that go beyond simply increasing active or passive ROM. So below I discuss a number of these benefits and attempt to discern whether active or passive training is more effective in certain circumstances.

Warming Up

Before you play a sport, having a good warm up routine is thought to be important (Fradkin, Gabbe, Cameron 2006; The National Sports Medicine Institute) . If you have ever played organized sports your coach or captain has probably put you through a routine to prepare your body for activity. When you are engaging in sport or exercise, having muscular strength is very important. Unfortunately, passive stretching has been shown to decrease your muscular strength, as well as your ability to run and jump. Active ROM training has been shown to have the opposite effect, and can increase power output (Page 2012). In addition to maintaining muscular strength, warm ups are frequently done to prevent injury, which is a topic worthy of its own consideration.

Winner- mobility training

Injury Prevention - Short Term

A mobile joint is a flexible joint, but a flexible joint is not necessarily a mobile joint. If someone only trains flexibility they may be able to apply force on a joint to make it move very far, but they will likely not be able to do it without the help of an external force. Someone who consistently trains their ROM with a more active approach is still lengthening their muscles, but they are also strengthening and increasing active capacity. Take the example of the wrist we used earlier on in the article…

If you start training wrist flexibility you might be very successful in pushing your wrist further and further back each day, but you likely will not see much of a change in your ability to actively bring it back because when passively stretching you are not engaging the muscles needed to generate that motion. But when you actively train your wrist every day you increase strength and the ROM of the joint. This is a key point when thinking about injury prevention. If you land on your wrist and have only trained flexibility, then the tissues within that area may not have the built capacity to deal with such an impact. But if you are properly actively stretching, you are training your muscles and nervous system and potentially even ligaments and tendons to be better adapted; so when you land on your wrist there is a better chance your body is able to handle the impact; you have made yourself more resilient (SSP; Kozen et al. 2021; Benjamin & Ralphs 1997; Wang & Cochrane 2001). Another example is volleyball players who use their shoulders very frequently, without proper shoulder mobility, the repetitive action of hitting, spiking, and serving was shown in a study to increase the risk of injury (Wang & Cochrane 2001).

Interestingly enough, being hyperflexible (which is confusingly officially referred to as hypermobility), is actually shown to increase rates of injury (Nathan, Davies, Swaine 2018). This shows that being very flexible without any active capacity will not necessarily protect you.

Winner- mobility training

Injury Prevention - Long Term

The less number of joint related injuries you sustain throughout your life the better off you are long term. Joint injuries, once they occur, make you more susceptible to re-injury, the prime example being ankle sprains (Mugno, Constant 2021). As people start to get older, the “use it or lose it” principle begins to apply even more (Hart & Zernicke 2020). Degenerating joint health can result in an inability to complete basic tasks that are essential for health such as cooking, walking, balancing, etc. For elderly populations, this can lead to a larger possibility of falling (NIA 2020). Also with increasing physical limitations comes a lessened ability to do things such as seeing friends and family, which could logically negatively impact mental health. Because mobility training, as discussed above, trains people’s ranges of motion more holistically (more parts of the anatomy are enhanced - particularly the nervous system) it would seem to be the best choice for long term injury prevention.

Winner- mobility training

Muscle Recovery

It is thought that when you stretch in pain free ranges of motion, whether actively or passively, you are increasing blood flow in that part of the body (Kato et al. 2020). Sidenote: the above claim is not universally accepted (Sands et al. 2013).

When circulation (blood flow) increases, your blood carries more nutrients to your joints and muscles, like oxygen, which is essential for recovery (Bangsbo & Hellsten 2002). But increasing blood flow can be accomplished with other modalities besides stretching: “Heat, cold, hot/cold contrast, hydrotherapy, massage, light exercise, electrical stimulation, and nutritional supplementation, rely heavily on increasing overall blood flow to sore areas of the body” (Sands et al. 2013).

Another aspect of muscle recovery that is important to address is the claim that stretching can reduce muscle soreness, but that is not even certain. One paper took the results from 12 different studies, one of which had over 2,300 participants. The studies were about the impact of stretching on muscle recovery and found that on average stretching reduced muscle soreness on average by 4%, which is an insignificant impact (Herbert, Noronha, Kamper 2011).

You may now be wondering, if stretching is not necessarily proven to be an optimal technique for muscle recovery, then what is? This is a topic worthy of its own article but it seems the most consistently reliable techniques for recovery are making sure to have proper sleep, nutrition, and hydration (Vitale et al. 2019; Mithal et al. 2013; Lorenzo, Serra-Prat, Yebenes 2019).

Winner- No Winner

Relaxation

The ability for the body to relax is dependent on the autonomic nervous system (ANS). The ANS is made up of the sympathetic nervous system (SNS - fight or flight), which is associated with stress and the parasympathetic nervous system (PNS - rest and digest), which is associated with relaxation. When we engage in exercise, we rely on the SNS to regulate our body (Katayama & Saito 2019). Because mobility training requires tensing of muscles, and can require high levels of intensity, it is certainly not conducive to induce a relaxed mood during the act, but it has been shown to induce PNS activity after completion (Inami et al. 2014). Passive stretching on the other hand has been shown to increase PNS activity, both during the act of stretching and afterwards (Inami et al. 2014). This is certainly a topic that could use more research, but it is intuitive that passive stretching would be more conducive to relaxation. After all, many yoga practices have been used to enter hyper relaxed states for hundreds to thousands of years.

Winner- flexibility training

Rehabilitation

Note: There are a number of variables that impact what method of recovery is best. Different people and different body parts may require different interventions for a number of reasons. Because of this variability it is difficult to make universal recommendations with regards to stretching as a form of rehabilitation (Page 2012). This is why if injured, it is important to see a trustworthy medical professional who will be able to guide you through the appropriate rehabilitation process.

When we suffer an injury, the body can exit its healthy alignment, and both passive and active stretching techniques have been claimed to aid in the body’s realignment (Page 2012). But injuries often require a period of time where the affected part of the body remains immobile. But remember: “You use it, or you lose it.” If we remain inactive, the affected part of the body will lose its resiliency, and as we discussed in the injury prevention section, mobility training is the more effective way to gain strength and holistic adaptation to new ranges of motion.

Winner- mobility training (but can vary)

Ease of Access

Passive stretching is certainly the predominant method in Western athletic environments for increasing ROM. Mobility training, and even what mobility is, is not widely known. Because there is more collective knowledge on passive stretching it is certainly easier to access if you want to develop a practice. Additionally, passive stretching requires much less effort because it involves less muscular tension and as mentioned above, is relaxing during the act, whereas actively stretching is not.

Winner- flexibility training

At the end of the day, if you train mobility, you also gain flexibility. If you can move actively in a ROM, you can also move in it passively, but the reverse is not necessarily true. Mobility training generally seems to bring the most benefits, and can be seen as a foundation for healthy and safe movement. But there are clearly benefits to passive stretching routines, namely its ability to quiet the stress mechanism of the body. So if you want to maintain relaxing and restorative practices that include passive stretching, it is important to do so! But try to build in a routine to boost your active ROM so that you can stay safe, strong, and flourish!

A reminder that this article is not a full review of the literature surrounding mobility and flexibility. There are certainly points that have been excluded, but this was an attempt to accurately portray many important pieces of what is known to be the differences between training active vs passive ranges of motion. Additionally, it is important to restate that what may work for one person where they are on their journey may not work for someone else for a variety of reasons. So make sure to conduct your own research specific to your needs, speak with knowledgeable people, and safely experiment with your own body.

If you want to get some ideas for an active ROM practice check out the following links:

My Article on Kinstretch

An article I wrote highlighting the Functional Range System’s mobility practice called Kinstretch. Here there are a variety of other links to dive deeper into this form of mobility practice.

YouTube Channel of a Kinstretch Instructor

Has a variety of CAR drills and explanations of concepts I’ve gone over in this article, such as irradiation and pain management.

If you want to get some ideas for a passive ROM practice check out the following links:

Yin Yoga Practice

This YouTube video is an hour long Yin Yoga routine. A form of yoga developed in the 20th century that focuses on longer stretch holds and deep breathing.

Quick Full Body Passive Stretch

This under 20 minute YouTube video goes over a full body stretching routine.