Can fancy-looking air-filled boots play a role in our workout recovery? I asked physiology expert Dr. Jeff Martin to take a deep dive with me to find out.
Recovery is a complicated fitness area to navigate. It means different things to different athletes, and each one has their favorite recovery ritual. The problem gets compounded when you introduce something as complex as compression. It can be applied statically or intermittently, and it varies from gentle pressure to very intense medical support. There are many factors to consider when you ask the question: does compression truly aid in athletic recovery?
To help me get through this topic and to help us understand how a device like the NormaTec external pneumatic compression systems works, I brought in Jeff Martin, Assistant Dean of Basic Medical Sciences and Associate Professor of Physiology at the DeBusk College of Osteopathic Medicine at Lincoln Memorial University, Knoxville, to help us along. As Jeff says, he has "had marked interest and has been involved in research with external pneumatic compression for quite some time now."
Let's start here: compression technology is confusing. To make matters worse, the message behind it can be misleading. The intersection of research and marketing creates confusion. Even professional sports coaches—who struggle to keep their players on the court, field, or ice—can't keep up with the real science. This is why we still see outdated activities like static stretching on the sidelines of football games and hear about ice baths administered during multi-stage triathlons.
Although the science is confusing, the anecdotes are clear—athletes like their recovery rituals.
What is compression?
In a nutshell, compression is simply applying circumferential pressure to the body using fabric or medical materials (like wraps or bandages).
Intermittent Pneumatic Compression (IPC) or External Pneumatic Compression (EPC) is essentially the same but more complicated. It is pulsating pressure that surrounds the body by using inflatable sleeves or boots. In theory, the sequence—or pattern that the pressure is applied with—will help with the circulation of blood and lymph, which is something that our circulatory system does extremely efficiently. At least in a healthy individual.
There's evidence to indicate that this process is indeed effective in disease models (or when applied to someone with compromised circulation), but the evidence gets more complicated when healthy and fit athletes are using these compression technologies. Just because compression helps someone with medically diagnosed circulation issues, will it also help someone with very good circulation like an athlete?
When I asked Dr. Martin about this, he replied:
You know, just because a healthy athlete doesn't necessarily have impaired circulation doesn't mean that augmenting perfusion or circulation to an exercised limb isn't going to be beneficial. And as a matter of fact, with some of the research, we've seen that absolutely seems to be the case. This kind of augmenting that helped to supplement the normal hyperemic response or prolonged the reactive hyperemic response after exercise is associated with some very favorable outcomes in recovery. From blood flow oxygenation, muscle oxygenation, to the removal of metabolites from exercise muscles. We have seen changes in terms of lactate clearance post-exercise, but also getting rid of some of those other metabolites, whether they'd be inflammatory cytokines or oxidative markers or just generally delivering oxygen, insulin, glucose and all the goodies that we need to help get back into a positive protein turnover situation.
When to use them
A runner friend of mine named Lucie, posted a video of herself on Twitter a while ago using a pair of the NormaTec boots. I emailed her and asked about it. Lucie had spent the last 20 weeks in Nike's marathon-specific training program, Project Moonshot, where athletes go after “far out” goals. Lucie's Moonshot goal was to run a sub 2:45 marathon and qualify for the 2020 Olympic Trials. And she came darn close, too!
She replied to my question, saying that she liked using the boots while she chilled out watching TV after a hard speed session or one of her longer endurance runs. She added that as the boots inflate, the pressure on her muscles "just feels good—kind of like a little air massage." She admitted that the results aren't drastic but she feels like using the boots speeds up her recovery.
When I pointed out to Dr. Martin that many of the athletes I know use the boots after a workout when they're at home watching TV, he said:
My informed opinion on this is the sooner you can do it after your workout ... the better in terms of getting all of the benefits from the NormaTec boots. That being said, anytime you're able to get into them, I suspect is going to give a significant benefit because of the laundry list of things I've talked about that occur that can be beneficial for an athlete.
Some people use the NormaTec boots as almost a preconditioning form. So they use them before exercising to kind of prime the pump in a more passive way without the metabolic expense of a warmup or walking, whatever it may be.
If you can't get into [the boots] right away, and you use them an hour or two hours later—or maybe you use them before you go to bed or in bed—there's still going to be a benefit. It's just that in terms of timing from metabolite clearance, immediately after or say six hours after, it could be optimized. That's part of the research that I think we need to continue to do is to optimize compression strategies, especially with external pneumatic compression, all the way from target inflation pressures to duration of the treatment to the timing of the treatment relative to exercise. All of those things can be, I think, tinkered with to better inform people. But regardless of when they're used, I do expect to see significant benefit.
The power of a hug
I agree with Lucie. When I use the boots NormaTec loaned me, the pressure on my muscles does "just feel good." My theory is that we humans like being squeezed. We comfort each other with hugs. We tightly wrap our babies with blankets. There is a whole new industry around weighted blankets for improved sleep quality and elevated mood. There is even some research on premature babies that indicates the touch of a human is enough to create positive health changes. And even though it is unclear how this relates, directly or indirectly, to compression, I think Lucie is on to something. There are definitely some physiological changes and some corresponding biochemical reactions happening here, and some of them may be in the central nervous system. I was even able to measure them in my Heart Rate Variability (HRV) readings.
And Dr. Martin agreed:
There have been some preliminary studies where I've seen abstracts or poster presentations at this point, but they certainly suggest that just a single 30-minute treatment with the NormaTec boots can change heart rate variability and autonomic output. I actually did a study—about two years ago now—where we looked at just treating a single leg with the NormaTec device and leaving the contralateral leg uncovered and uncompressed. And in that study, we saw that yes, you still get these profound effects in the treated leg, but we were actually getting pretty significant effects in the untreated leg as well. And part of our working theory for why that goes beyond just fluid mobilization. It was changed in what we're seeing from a nervous system output standpoint.
So, between that and what we've observed with heart rate variability, I think you're absolutely correct. And you know, interestingly, when you mentioned the fact that you feel kind of happier or you feel good, I think that's a huge benefit to an athlete as well. There's something to be said for just feeling better. You feel better going into a workout or a race or whatever it may be. I think there's enough to suggest that that's going to be highly beneficial for performance.
What does science say?
A 2017 study concluded:
External pneumatic compression (EPC) reduces muscle soreness and attenuates reductions in flexibility, albeit the mechanisms through which this occurs need to be further elucidated. Likewise, the potential EPC-induced reduction in muscle proteolysis (the breakdown of proteins into smaller polypeptides or amino acids), as well as oxidative stress, warrant further mechanistic research.
A study in New Zealand looked into what biological systems showed signs of recovery by looking at muscle power after NormaTec treatments. The researchers used jumping performance as their easy-to-measure factor and found "IPC did not attenuate muscle force loss following a bout of strenuous eccentric exercise in comparison to a control."
But more recent science suggests that the lymphatic system, an understudied part of the body, might be signaling the brain to simply feel good in a systemic fashion. This makes a good case for the idea that many of the anecdotal feelings of recovery athletes get when the lymph fluid is squeezed using IPC is actually just the central nervous system (CNS) responding. So again, we are back to "it just feels good."
Dr. Martin weighed in with some new science, adding:
Probably one of the more exciting things that I've seen in research, which again, is still fairly preliminary ... We've seen evidence from a few different studies—now all relatively small in terms of their size—but we saw indications that markers of proteolysis, which is protein breakdown, have been reduced with NormaTec treatment concurrent with intense exercise, whether it be intense and direct exercise like HIIT training or overload resistance training exercise. We've seen a decrease in these markers of protein breakdown, which seems to suggest maybe the NormaTec boots are helping to favor protein turnover in a positive way. With exercise, we create a lot of micro-damage, and the response to that micro-damage, and the rebuild, is really where we get the benefit. And it looks like this might help tip things in favor of hypertrophy (muscle growth) or muscle repair.
The NormaTec device
NormaTec is basically a set of inflatable pants that push air in a sequence. There are hip and arm attachments available, but honestly, I have never seen a pair. The leg version is by far the most popular.
Each session cycles through the pattern of sequential compression, and the user is able to adjust both the duration and the amount of pressure. You can use the devices on-screen controls or sync it with your smartphone and control it using an app.
Dr. Martin says:
The NormaTec device uses a peristaltic type of compression, which, as the term suggests, is more like muscle contraction. And anything that mimics normal physiology, typically associated with better outcomes. So, for a lot of those reasons, I was attracted to the NormaTec devices and have been looking into their physiological effects for quite some time. Now, in terms of where we're at in science, I think we're still just scratching the surface. I think there's a lot more work that can be done in terms of optimizing how exactly we're doing compression. I think we know that there's a kind of benefit, but there's still a lot of questions that we can answer.
Why spend money on inflatable boots?
Sleep, nutrition, and time truly are the most important factors for fast and thorough recovery, with pretty much all other modalities coming in a distant fourth place.
So why do athletes love NormaTec and compression even though the research is scattered, mixed, and even conflicting? Dr. Martin has this to say, which I think sums it up nicely.
I think anybody that tries the boots will know that they're there working. You're going to feel that blood flow is increased to your legs and you feel a little bit more ready for exercise. And if you're in the throes of training and you're sore, I think you're going to notice some pretty immediate effects in terms of what's going on with soreness and flexibility or range of motion. And then, what you alluded to—you just generally tend to feel better. I know that when I use a device, I tend to feel better afterward as well, and I feel like I've done something good for my routine.