Physical Therapists Using Clinical Analysis To Discuss The Art And Science Behind Running and The Stuff We Put On Our Feet

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Body Weight Support Running: Benefits and Uses
By Global Brand Manager, Nathan Brown PT, DPT, OCS

Running has become one of the more popular forms of exercise over the last 30 years. Given this increase, we are also seeing a rise in the number of people injured while running. While there is a lot of debate around the leading causes of injury, there is some consensus. The first is that the highest risk for a future injury is a previous injury in the last 12 months. Other potential causes include training errors, such as changing your training volume too quickly, high running mileage (>40 miles/week), and cumulative stress placed on the body in areas of weakness or limited mobility. Given the main finding that the most predictable risk of future injury is an injury in the past 12 months, the utmost care and attention should be given to the recovery process from an injury and how you go about returning to running. There are many factors that go into being a healthy runner regardless of if you are just starting out, have never had an injury, or are returning from injury. Today we want to discuss just one tool to support runners in their pursuit of being healthy: body weight support. 

Aqua jog

What is Body Weight Support?

Body weight support is any mechanism that decreases the amount of impact forces through the body as we run. In general, the impact forces that need to be supported by our muscles, joints, and tendons are 3-8x our body weight. This is a lot of demand on our bodies. Body weight support is any sort of system that decreases the amount of mass or body weight that contributes to impact forces.

There are many mechanisms to achieve body weight support, but here are three that I have used clinically and for personal use. 

Deep Water Running: this method completely removes body weight. Contrary to what many may think, in this scenario, your feet are typically not touching the ground, but it is done in the deep end of the pool. Typically this is done with a floating belt and having the runner perform elliptical motions with their legs to simulate running. The technique requires focus to achieve the running motion, and often you will be slowly moving through the water. It is tempting to use your arms for propulsion, but really all the work should come from your legs. I’ve also found using a noodle looped in the back of the belt helps with achieving a bit of a forward lean.    

PROS: Complete removal of body weight support, proven maintenance of fitness for 6 weeks in trained athletes 
CONSIDERATIONS: requires pool or water access, the technique is important and can easily be done incorrectly, it places higher stress on hip flexors and hamstrings (not as appropriate for those at certain phases of recovery from certain tendon pathologies), removes all impact forces and therefore doesn’t provide benefits of impact activities (i.e. for improving bone health) 
WHO IS IT BEST FOR: For those who have access to deeper water, this is the best option when complete avoidance of weight-bearing is required during a recovery process. It also is proven to maintain fitness for someone close to a race event. 

LEVER PRO Running System (Treadmill Harness Systems): this is a method where a harness system is attached to a treadmill that utilizes bungees to offload a runner through a special pair of neoprene shorts. The LEVER PRO system can offload a runner up to 45# and is adaptable to various treadmills.

PROS: A mobile system that is adaptable to many treadmill types (has a nice carrying case to bring wherever you need to go), allows the runner to maintain impact forces while still offloading some weight, more cost-effective than some other methods ($1,109 + $99 for shorts), easy assembly, multiple uses for rehab/recovery/training progression, compatible for many runner sizes and body types, can be used for walkers 
CONSIDERATIONS: Non-specific offloading amounts (unable to determine exact pounds), bungees do stretch over time decreasing max capacity, requires treadmill compatible with the system 
WHO IS IT BEST FOR: For someone wanting their own access to body weight support that is also mobile, this is a great option. It is cheap in relation to other options, but does not provide specific offloading characteristics and is more of an estimate. Therefore it is best for someone recovering from an injury that doesn’t have specific weight-bearing restrictions. It also is a nice tool to have on hand for increasing mileage with some decrease in impact forces.  

ALTER G: This is a specialty treadmill that utilizes positive air pressure to offload a runner through a carriage, specialty shorts, and the treadmill bag. The Alter G can offload a runner up to 80% of their body weight at 1% increments.   

PROS: Very specific body weight alteration through a calibrated system, the highest percentage of offloading capacity, integrated training programs, gait metric analysis through sensors in the treadmill, wide population applicability due to high offloading capacity, video footage (frontal plane) during running 
CONSIDERATIONS: Very expensive ($35,000+), mode of offloading can feel unnatural at times, can be difficult for some to get into with certain mobility deficits 
WHO IS IT BEST FOR: For someone who has access through a local PT clinic, this can actually be an affordable option as you pay per session or for time. However, not many places will have this kind of access. On their website, you can click on the "Find and Alter G" tab to see if there is one near you. Therefore it is best for those requiring specific weight-bearing status (such as postoperatively) or for those who need very high levels of weight taken off. It also is beneficial in other cases outside of runners, but I will discuss those later. 

Lever Pro
What are Some Common Uses for Body Weight Support Training? 

Rehabilitation:  As a physical therapist, this is my most common application of these types of devices/strategies. Depending on the type and severity of the condition, the “tool” of choice may change. Here are two examples.  

First, if someone has Achilles tendinopathy (pain in the Achilles region), it is important to appropriately load the tendon while it heals. This means that a runner will likely need to decrease the loading a bit, but complete removal of load is not necessary. If a runner tries to improve an Achilles tendon issue by resting alone, it will not get better (or it will feel better for a bit, and then the pain will return right after getting back to running). A runner can continue to run as long as they follow the pain monitoring model. However, it may not be possible to run within these parameters overground, and an option like the LEVER system or an Alter-G would be a great option to continue running with decreased loading that keeps you within the rules of the pain monitoring model. If a runner cannot run even with body weight support and follow those rules, that is where the use of a pool would come into play. 

A second scenario would be someone with a bone stress injury. The optimal loading here, unlike in the case of tendons, requires no pain during the activity. If there is pain, the bone will not heal. Therefore early intervention will often be with the use of deep water running. In some cases, an Alter G may be useful given the ability to offload more, but the drawback is that at lower body weight, you have to run at significantly higher speeds to achieve the same cardiorespiratory effects.  

Additionally, body weight support in rehabilitation can be used for more than just running. It can allow you to do heel raises, single leg squats, step-ups, or other exercises with a bit of offloading if doing these exercises is too painful without the support. Body weight support is a potent strategy for load progression of impact and non-impact activities during rehabilitation.  Advancing Training (for new or experienced runners):  Another use of body weight support can be to start a new running program. This could be for completely new runners doing a couch to 5K or experienced runners wanting to up their weekly mileage for marathon training (or some other longer distance than they previously have done). Since body weight-supported running places less demand, it could be a great way to perform a recovery run the day after a workout or to add a double for the first time. The overall demand on your muscles, tendons, joints, and the cardiorespiratory system is lower, and therefore it is a more incremental way to progress your training.  

One thing we see with running-related injuries is there is sometimes a 4-6 week delay of injury onset after starting a new running regimen, which makes it difficult to predict whether an injury is impending or not. This is because cumulative fatigue and tissue injury threshold lower as we continue highly repetitious activities (see Figure 1 in this study). And although impact forces are not necessarily a direct correlation with all injuries, cumulative stress (over those 4-6 weeks) on tissues that are not robust enough may lead to injury. Therefore, body weight-supported running would be a way to gradually introduce higher loading levels.  

Does Body Weight Support Still Help Improve Fitness? 

This question is a bit more complex than meets the eye, but we will try to keep things a bit more simple here. First, I mentioned above that there is good evidence that deep water running is able to maintain fitness for 6 weeks. The bonus is that this showed that maintenance in trained endurance athletes and people who were less trained had even more benefits. There are other influences on the cardiorespiratory system during deep water running, and you can check those out in this study

Now comes the question of other methods like the Alter G and LEVER System. Some research has found that you are able to challenge the cardiovascular system in similar ways that you do overground (without body weight support), but you have to be running significantly faster than you did overground and current research hasn’t examined anything lower than 85-95% of your total body weight. The conclusion of one study suggests that the use of “overspeed running programs” could elicit similar cardiorespiratory responses to overground. To give some context, one example would be that to elicit the same response of running 8mph (12.9km/hour) overground, you’d have to run 10mph (16km/hour) if at 80% body weight on an Alter G (you can find more examples in this study). This may be all well and good for people using body weight support for training, but overspeed running programs probably aren’t a feasible option for those recovering from injury.  

To sum things up, the use of body weight support on a treadmill will elicit some cardiorespiratory demand, but it will be overall lower than running overground if running the same speed. Again, this can be beneficial to limit the amount of lost fitness during recovery and also may be used as a way to add a recovery or easy run to your week. However, it has less of an ability to maintain fitness while rehabilitating when compared to deep-water running.   

Sample of Aqua Jogging
Does Body Weight Support Change Mechanics? 

Finally, let’s discuss how the use of body weight support (Alter G or LEVER System) may affect your running form. A change in the amount of body weight does result in some predictable changes in running mechanics. The first is a decrease in cadence. While in a body-weight-supported situation, your muscles still have the same capacity to produce force. Therefore each propulsive effort leads to further flight time and longer step length. This results in a lower cadence at any given speed and decreases further the more weight is taken off in a linear fashion. With each 10% of body weight taken away, there is a 1.5-3.5% decrease in cadence.  

Does this decrease in cadence matter? Maybe not. First, the study above also found that with cognitive focus the subjects were able to return to their typical overground cadence. So if you want to maintain your cadence, you can…you just need to give some focus. Second, cadence is not the only change. With increased support conditions, hip and ankle range of motion and vertical displacement decreased. The concern with decreased cadence (if there is one) is that running at a cadence 5-10% lower than your natural cadence leads to increased demand on the calf, hip, and knee musculature. However, cadence is not the only change in body weight support conditions. The decreased range at the hip and ankle as well as decreased vertical displacement offset the “concerning” increase in forces from decreasing cadence. All that on top of the obvious fact that there is indeed decreased weight overall. 

So yes, there are biomechanical changes with body weight support. However, they should not be of concern and the biggest takeaway would be to avoid analyzing your gait in body weight-supported conditions because they will not be indicative of your overground mechanics.   

Clinical Pearls:  Clinical use of body weight support also cannot be ignored. I have used body weight support for many patients with different types of conditions over the last 7 years. The big picture is that tools like the Alter G and LEVER system allow you to modify weight for progressive resistance exercises or gait training. Therefore I like to use it in some of the following situations (and more):  Post Operative: I often use body weight support to start both double and single-leg closed-chain exercises. Then I use it to return to plyometric activities such as hopping. I’ll have people perform squats, single leg squats, and also place a step on the treadmill and perform step-ups and lateral step downs (this can be done in the Alter G as well, you just cannot start the treadmill belt).  

Deconditioned: When working with people who have severe deconditioning, I’ve found body weight support to be a great way to reintegrate a walking program.  Neurological Conditions: For people with certain neurological conditions (such as CVA), high repetition and high-intensity training are important. Therefore I use body weight support to increase the number of gait repetitions that we can achieve during a session while maintaining a higher intensity and decreasing rest breaks. I’ll also use it to work on increasing gait speed.  

Balance: For people with fall risk (whether neurologically caused or otherwise), I appreciate using body weight support because it provides an extra level of support that allows for training gait in a more controlled environment. It also allows for static balance training (narrow base of support, tandem stance, single leg stance, etc) on a stationary treadmill.  There are many other applications of body weight support beyond simply run training. If you are a clinician, it can be a potent tool for your a wide variety of people you may see in your clinic.      


Gojanovic, B., Cutti, P., Shultz, R., & Matheson, G. O. (2012). Maximal physiological parameters during partial body-weight support treadmill testing. Med Sci Sports Exerc, 44(10), 1935-1941. 

Hreljac, A. (2004). Impact and overuse injuries in runners. Medicine and science in sports and exercise, 36(5), 845-849. 

Kline, J. R., Raab, S., Coast, J. R., Bounds, R. G., McNeill, D. K., & De Heer, H. D. (2015).

Conversion table for running on lower body positive pressure treadmills. The Journal of Strength & Conditioning Research, 29(3), 854-862. 

Millslagle, D., Levy, M., & Matack, N. (2005). Comparative kinematic measures of treadmill running with or without body weight support in runners. Journal of sports science & medicine, 4(4), 583.

Reilly, T., Dowzer, C. N., & Cable, N. T. (2003). The physiology of deep-water running. Journal of Sports Science, 21(12), 959-972. 

Saragiotto, B. T., Yamato, T. P., Hespanhol Junior, L. C., Rainbow, M. J., Davis, I. S., & Lopes, A. D. (2014). What are the main risk factors for running-related injuries?. Sports medicine, 44(8), 1153-1163.

Stockland, J., Giveans, M. R., & Ames, P. (2019). The effect of an anti-gravity treadmill on running cadence. International Journal of Sports Physical Therapy, 14(6), 860.


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