You've likely seen runners wearing high compression socks or calf sleeves, or experienced that encased sausage feeling yourself when trying to squeeze into a pair of compression shorts or tights. The claims: They'll make you run faster, jump higher, and recover better after exercise. But do they really work? And if so, how can a simple pair of pants make so much of a difference?
"The theory is that compression on top of the skin and underlying muscle will have a positive effect on increasing the movement of oxygen in the blood, thus enhancing your performance," says Michele Olson, Ph.D., professor of exercise science at Auburn University Montgomery. Oxygen is an essential component of your workout performance—during exercise, your muscles are working harder; therefore, they need more oxygen to fuel the cellular respiration process which gives you energy. It's the reason you're sucking in air at a faster rate during your run. That oxygen is carried by your blood to your muscles, which convert it into energy. So good blood flow is pretty important.
And compression really does increase blood flow. In fact, doctors have been using it for years in patients with poor leg circulation and varicose veins. "The tight socks help blood vessels to constrict and return the blood up toward the heart instead of that blood pooling in the legs, creating swelling and hampering blood flow to the muscles and organs in the rest of the body," says Olson. (Related: Why Fit Women Get Blood Clots.)
Apply that same idea to athletic wear and you should see the same results, right? At best, the research on compression's effect on performance is mixed, says Olson. A 2011 review of studies on several types of compression concluded that there are no scientific indications regarding the benefit of compression garments in competitive sports. Recent research in the International Journal of Sports Physiology Performance looked specifically at the effect of calf sleeves and found they did not enhance performance or running economy. Still, some studies have seen a slight improvement in jumping performance.
Probably the best effect of compression is actually during recovery. "Because compression restricts blood vessels, it can cut down on swelling, which stiffens the muscles and joints, making it harder to work out the next day," says Olson. Plus, since your muscles experience micro-tears during hard workouts, causing inflammation, having the support of compression clothing can reduce delayed-onset muscle soreness. (Really hurting? Get even more tips on How to Recover from a Tough Workout.)
So really, you're better off donning compression after your workout to speed up recovery and decrease soreness.
If you're already a fan of wearing compression gear during your workouts, this doesn't mean you need to stop, especially if you feel that it really does make you run faster or squeeze in a few more reps. "The few studies that have found positive changes in performance due to compression were actually correlated to the placebo effect," says Olson. So if it makes you feel better, go for it! Otherwise, save the compression tights for part of your post-workout recovery.