Alex Hutchinson draws on the latest research to answer your fitness and workout questions
in this biweekly column on the science of sport.
THE QUESTION
Will compression pants and knee socks make me fitter and stronger?
THE ANSWER
From basketball players wearing compression shorts and sleeves on their shooting arm to marathoners racing in knee-high socks, there's a lot of tight clothing in the upper echelons of sport these days. And the reasons vary.
"It has become evident that one garment does not do all things," says William Kraemer, a professor at the University of Connecticut's Human Performance Lab and past president of the U.S. National Strength and Conditioning Association.
The wave of colourful spandex that engulfed gyms in the 1980s offered benefits such as cooling, sweat management, reduced chafing and (ahem) better support, Dr. Kraemer notes. The current vogue is focused on bolder claims of enhanced power, better endurance or faster recovery, depending on the garment.
Attempts to verify these claims have reached conflicting conclusions, in part because it's so difficult to control exactly how much compression is applied to different body shapes. But it's increasingly clear that these garments do something.
The new generation of compression gear is descended from medical leggings that have been used for decades to treat blood clots and certain circulatory disorders. The key is that these garments deploy "graduated" compression: They squeeze more and more tightly the farther they are from the heart. Such leggings help reduce blood pooling in the legs and speed the return of blood to the heart.
One of the clearest benefits compression offers for athletes is quicker recovery from "delayed onset muscle soreness" - the aches that appear after an intense bout of unaccustomed exercise. Wearing a compression sleeve around the affected muscles helps control swelling and, through enhanced circulation, hastens the removal of cellular waste products.
More controversial is the research into explosive movements such as sprinting and jumping. A 1996 paper by Dr. Kraemer's group found that volleyball players wearing compression socks were able to produce more power in their vertical jumps. One theory is that the physical support offered by the garment reduces unwanted oscillation and jarring of the muscle - that's the rationale behind compression shorts for basketball players, though studies in the past decade have produced conflicting results.
For endurance athletes, the key mechanism is the "calf muscle pump" - with each step or pedal-stroke, the clenching and unclenching of the calf muscle squeezes blood back toward the heart. Compression socks covering the calf provide an extra squeeze that enhances this pumping action, speeding the flow of much-needed oxygen to working muscles.
Sure enough, a recent study in the International Journal of Sports Physiology and Performance found that 12 cyclists performing a one-hour time trial improved several physiological markers, including muscle oxygenation, when wearing full-length graduated compression leggings. The problem is that their performance in the time trial wasn't affected at all.
In contrast, a forthcoming study in the Journal of Strength and Conditioning Research found that runners in below-the-knee compression socks ran farther and faster in a treadmill test, but didn't show any change in key physiological parameters such as aerobic capacity.
Part of the problem is that studies are using slightly different garments.
"No one has really figured out the definitive pressure to improve performance," says Aaron Scanlan of Australia's Central Queensland University, the lead author of the cycling study. Even within studies, the garments fit different people with varying amounts of compression.
For now, it remains a bit of a crapshoot whether you'll happen to have calves that are precisely the right size for the compression socks you buy - but it's encouraging to know that, in principle at least, they work.
Alex Hutchinson blogs
about research on exercise
and athletic performance at
***
Squeeze play
Athletic compression garments apply "graduated compression" (represented by white arrows), in which the tightest squeeze is applied farthest from the heart. The goal is to speed the circulation of blood back toward the heart and clear away metabolic waste products from the muscles.
Increased compression, particularly in the extremities, also wraps key muscle groups to reduce muscle movement and vibration. Some researchers believe this can minimize soft-tissue damage, reducing DOMS (delayed onset muscle soreness) and speeding recovery.
OTHER GARMENT FEATURES:
Improved blood flow increases the oxygen supply to working muscles, which may prolong endurance.
Most are made from material designed to wick away sweat and moisture. Fabric may also have anti-bacterial properties.
Garments provide thermoregulation, allowing your body to stay cool in hot conditions, and vice versa.
Many are rated SPF 50 or higher for safety in the sun.
Improved blood flow increases the oxygen supply to working muscles, which may prolong endurance.
Socks with graduated compression can help reduce the pooling of blood in the legs, which is why many athletes wear them during long plane flights to prevent lower-leg swelling. Socks that come up to the knee give the calf an extra squeeze that helps pump blood to the heart - so much, in fact, that some researchers believe there's no additional benefit to wearing compression leggings that go all the way up, says Central Queensland University researcher Aaron Scanlan.
The squeezing of the calf muscle constricts the blood vessels, and with the help of one-way valves above and below the calf, blood gets pushed back toward the heart with each step.
COMPILED BY ALEX HUTCHINSON.