Compression wear has been around for a long time in the medical field. They are typically socks or stocking of various lengths made up of various materials. They provide graduated compression against the leg.
The purpose for them is to place pressure on blood vessels which will constrict those vessels. This forces the blood to flow through a smaller canal, increasing the blood pressure in the legs forcing blood back up toward the heart.
The main benefit is to prevent blood and fluid from pooling in the lower leg which reduces swelling and may help reduce or even prevent varicose veins. Many triathletes have started wearing compression socks during and after hard workouts or competition with the intent of improving athletic performance and recovery.
Only a few independent studies are available regarding the effect of compression clothing on endurance athletics. Many of the manufacturers have created "studies" of their own, but I am leery of these results since they stand to benefit financially from a favorable outcome. Zoot seems to have the most comprehensive study available to the public, but again, I am taking their test results with a grain of salt.
One independent study from the Journal of Sports Sciences tested compression stockings in January of 2007. This study tested 14 individuals. After two separate 10K time trials, no performance enhancement was shown, but 13 of the 14 participants indicated reduction in delayed onset muscle soreness 24 hours after the test. This is a significant outcome, but based on athlete perception, not measurable data.
Another study in May of 2007 tested 10 individuals by measuring maximal oxygen uptake, heart rate, blood lactate concentrations and ventilation. This test seems to have the most data available by way of metrics for which to analyze. No statistical difference was observed during exercise with compression socks. However, there was a statistical difference in recovery of blood lactate concentrations after the test was completed while wearing the compression socks.
A third study in May of 2009 only tested the effect of compression clothing on performance. They utilized a variety of garments including compression socks, tights and full body wear. There was no statistical effect on performance.
So what does this mean?
This means that compression wear does not seem to have any effect on performance if worn during the activity. However, there may be a positive effect on recovery if worn after the activity. They may also help reduce swelling after long periods of sitting or standing. Many athletes have reported "feeling fresher" after wearing the socks post workout or during travel.
There is a wide variety of compression ratings as measured in millimeters of mercury abbreviated as mmHg. This mmHg rating is a universal measurement of atmospheric pressure. However, there is a large discrepancy between manufacturers and their recommendations.
Also, the pressure rating can vary from one person to the next based on garment size and circumference of the leg. No significant data is available to determine the most appropriate range for athletes.
The Bottom Line
If the socks feel good to you during a race, wear them. After all, if you feel fast, you will probably go faster. (That's an entirely different article about psychological impacts on performance so we won't cover that now.)
I would not recommend wearing them during training. If they work as advertised, this could potentially limit the stress and adaptation that athlete's desire. In other words, save it for race day. I do recommend they be worn during long trips or long durations of sitting or even standing (think: desk job, nurse or during travel to a race).
I also recommend the socks be worn for an hour or two after a hard workout. This could help aid in recovery. Many sport apparel companies have begun producing compression wear. If you can do without the logo of your favorite brand and want to save some coin, go to any pharmacy and buy the $5 pair of medical compression socks. They come in black or white so they look similar to the more expensive sport brands.
Journal of Sports Sciences, volume 25, issue 4, January 2007 pg 413-419
Medicine and Science in Sport and Exercise, May 2007 Volume 39, issue 5
Medicine and Science in Sport and Exercise, May 2009 Volume 41, issue 5
Ken Axford is owner and head coach of PEAK Multisport based in Colorado Springs, Colo. He holds certifications from USA Triathlon as well as USA Cycling and the American Council on Exercise. For more information, visit http://peakmultisport.com or PEAK Multisport on Facebook.
This article was originally published in USA Triathlon Life magazine. USA Triathlon is proud to serve as the national governing body for triathlon--the fastest growing sport in the world - as well as duathlon, aquathlon and winter triathlon in the United States. Visit usatriathlon.org.