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In 2014, I walked into a small hotel in Italy to meet the other men on the U.S. Mountain Running Team. My eyes landed on their thighs: Every single one of them was wearing compression tights. A couple of days later, during the race, about half the team wore knee-high compression socks.
Many elite athletes use compression for travel, recovery and/or racing, but just as many think it’s unnecessary. So who’s right?
Blood, like most things other than Kilian Jornet, is subject to gravity. As a result, it can pool in the feet and legs, reducing blood flow and slowing the clearance of chemical byproducts.
Stephanie Howe, a Ph.D. in Exercise Science and the 2014 Western States 100 champion, says that during travel, the lack of movement and pressure differences can cause fluid build-up in the lower legs. This can lead to fatigue and “heavy legs,” as well as acute issues like deep vein thrombosis (DVT)—blood clotting that can cause extreme discomfort and occasionally death—which athletes are especially prone to.
During activity, Howe says, we have a “muscle pump” that returns blood to the heart. When you’re at rest, compression (especially graduated compression, which applies different degrees of pressure to different areas) can get the blood moving in a similar way, reducing pooling and lowering the risk of DVT.
Recovering after a run involves two inter-connected variables. Perceived soreness, a subjective response to a physical phenomenon, is partially dependent on a runner’s psychology. Muscle damage and inflammation, meanwhile, are physiological responses to physical stress, and can be measured objectively. Both psychology and physiology are important to subsequent performance.
A 2016 study in the journal Sports Medicine reviewed the existing literature on compression. While there was not agreement across all studies, there were statistically significant patterns. Wearing compression gear after activity did slightly reduce muscle damage and inflammation. The largest effect, though, was a reduction in perceived leg soreness and a delay in the onset of muscle fatigue. In other words, the physiological effect is small, but the psychological effect—how sore you feel—is large.
Emily Kraus, a sports-medicine doctor at Stanford University and the winner of the 2016 Sean O’Brien 50K, says that, despite great variability in the literature of compression overall, it is mostly settled when it comes to recovery. “Personally,” she says, “I like the nice ‘squeeze’ of compression stockings after a race or training run, and agree with the current research that states there is a psychological benefit.”
One key element of running fast on the trails is running economy, or how much energy it takes to do a certain amount of work. To visualize how compression gear might help running economy, think of glass wrapped tightly in bubble wrap before shipping, so it’ll be less likely to shatter. In theory, compression worn during exercise could work similarly, reducing the force absorbed by working muscles and improving how muscles contract.
In practice, the Sports Medicine review found, the evidence for improved performance is mixed. Wearing compression during exercise did have a small positive effect on running economy, as well as on perceived exertion and lactate clearance (which could speed recovery between high-intensity bursts). But there was no impact on numerous other variables, including oxygen uptake, heart rate, heart-stroke volume and the most important one of all—actual running times.
Based on the research, Kraus isn’t convinced that there is a substantial positive benefit to wearing compression when running. At the same time, she says, “The risk of harm is minimal, but be sure you choose the correct size to avoid going too tight.” Too-tight compression can actually impede blood flow during activity by cutting off some circulation, Howe says.
One negative singled out by the Sports Medicine researchers was that compression caused a moderate increase in body core temperature. Howe explains that compression can reduce evaporative cooling, the main way the body keeps its temperature in check. Especially in longer races, this could lead to overheating and thereby compromise performance.
So, were the runners of Team USA right to compress? There are some established benefits, especially for travel and recovery, but there is no definitive answer. Find what works for you. If you are prone to overheating, compression might not be right. But if you have a cold-weather race and the snug feeling seems to improve your running economy, compress away.
David Roche is a two-time USATF trail national champion, the 2014 U.S. Sub-Ultra Trail Runner of the Year and a member of Nike Trail Elite and Team Clif Bar. He works with runners of all abilities through his coaching service, Some Work, All Play. Follow David’s daily training on Strava here, and follow him on Twitter here.
This article originally appeared in our July 2016 issue.