The Science of Compression Gear for Runners
One of the big fads recently in the running world is compression wear. Whether it’s compression shorts for sprinters or compression socks for marathoners, it’s hard to attend an athletic event without seeing somebody decked out in skin-tight gear.
As with all fads, the makers of these products brag about the performance-enhancing properties of their apparel. But, there is some legitimate science that’s investigating the utility of compression wear too – and that’s what we’ll look at today.
How Compression Gear Works
Compression wear was initially developed as a treatment for swelling disorders like lymphedema, where limbs swell up like balloons because the body’s lymph drains don’t work properly. Compression was quickly adopted to treat vascular issues as well: doctors found that graduated compression stockings (a knee-height sock in which compression is the highest at the ankle and tapers off towards the knee) helped manage varicose veins and helped to prevent blood clots in bed-ridden patients after surgery.
Compression socks accomplish this task by creating positive pressure across the various one-way valves in the blood veins. The difference in pressure between the ankle and knee encourages blood in the veins to flow back towards the heart and counters the effects of gravity, which can cause blood to pool in the veins of immobile patients (for this reason, frequent air travelers are sometimes advised to wear compression stockings to reduce the risk of deep vein thrombosis during long-haul flights).
But it wasn’t long before runners began to take interest in the effects of graduated compression on endurance performance. Perhaps spurred by the now-ubiquitous compression shorts worn by sprinters (which some studies have shown to increase jumping ability), exercise physiologists started investigating whether compression socks—referred to in the literature as compression stockings—had any effect on performance or recovery.
The Science of Compression Gear
Compression gear and soreness
One of the earliest studies on the matter was conducted by Ajmol Ali et al.1 at Massey University in New Zealand. His 2007 study used two experiments to test the effects of compression socks, each using a (separate) group of 14 recreational athletes.
The first experiment was a gym-class-style “shuttle run” test, followed by an hour’s rest and another identical shuttle run. The participants then returned 24 hours later and were evaluated on soreness and muscular pain. This was repeated three days later. In one trial, the subjects wore compression socks; in the other, they wore regular ankle-height running socks.
The second experiment was a 10-km training run on the roads with a similar evaluation of fatigue and soreness 24 hours later.
While the shuttle-run experiment showed no difference in any variables between the compression socks and the regular socks, the 10km run experiment showed a marked lessening in soreness for compression sock users. There was a slight trend towards faster times and lower heart rates in the compression wear, but these were not statistically significant.
Compression gear and endurance
Ali’s work spurred further studies into the effects of compression socks. One of the first to directly investigate their effects on a maximal running effort was published in 2009 by Wolfgang Kemmler and coworkers in Germany.2
In it, 21 “moderately trained” runners (average 10k PR of about 40 minutes) completed two maximal effort treadmill tests, one wearing compression socks and another wearing regular running socks (presumably ankle-height).
Unlike Ali’s study, Kemmler’s group did find a slight improvement in endurance in the maximal treadmill test, but only a small part of this was explained by an increase in oxygen intake. The authors proposed that the compression stockings increased the mechanical efficiency of the runners.
Compression gear and maximum heart rate
At this point, it still isn’t clear what the exact benefits of compression socks are. A more comprehensive study published last year by Adrian Varela-Sanz et al.3 at the European University of Madrid attempted to clarify this. It used more experienced runners (10k PRs averaging 37-38min for men and 43-46min for women) and 26 subjects in total.
The subjects’ efficiency and oxygen consumption were monitored as they ran on a treadmill, first in four 6-minute bouts at half-marathon pace, then in a run to exhaustion at about 5k pace.
The compression socks had no statistically significant effects on running economy or performance, but like Ali’s 2007 study, a nonsignificant trend was seen towards slightly improved economy and performance in the compression socks. There was, however, a notable change in maximal heart rate: during the run to exhaustion, the runners had slightly lower heart rates at 5k pace than the runners in regular socks (a desirable effect).
Validity of scientific research on compression gear
One major flaw of all of these studies is that they did not adequately control for the placebo effect. There was no way to tell if the prospect of a high-tech knee-high sock, which was obviously different than a run-of-the-mill ankle-height running sock, was independently affecting the measurements. And since the observed effects for compression socks are comparatively small, the placebo effect could be having a significant impact on the study’s results.
Last year, Ajmol Ali published a more rigorous investigation of compression socks and running performance, one which aimed to eliminate these control issues.4
In this study, twelve runners participated in five 10km time trials on an outdoor track. The first was a familiarization trial, and the next four investigated various compression socks. One was a “control” sock, which, while being a knee-high sock like the real compression socks, did not significantly compress the lower leg. The other three were socks with “low,” “medium,” and “high” degrees of compression. Before and after each 10k time trial, a vertical leap test was administered to measure the runners’ ability to generate explosive power.
None of the various levels of compression wear had any effect on performance, lactate accumulation, or heart rate; however, the low and medium-level compression socks prevented the runners from losing maximal muscular power during the 10k time trial.
While runners in the non-compressive socks and runners in the high-compression socks both experienced a drop in their vertical leap height after their 10km run, the runners in medium and low-compression socks actually increased their leaps, indicating they had better-preserved their explosive power (which would perhaps prove useful in a sprint-finish). This may also have implications for recovery, since presumably their leg muscles were less fatigued in the time trial in the low and medium-compression socks.
Is compression gear worth the money?
One thing’s clear: compression socks aren’t a game-changer. There’s some evidence they could increase your performance by a small amount, but their best use is probably in preventing excessive soreness and muscle damage from hard training sessions.
While the effects on performance were not consistent across the studies we’ve seen here, a small protective effect does seem to emerge: the runners in Ali’s first study reported less soreness 24 hours after their workout, small shifts towards more energetically efficient running were seen in Kemmler’s and Varela-Sanz’s studies, and muscles seemed to retain more power in Ali’s second study.
So, if you’re willing to shell out the $50-60 for graduated compression socks, you should wear them for your toughest hill workouts, longest runs, and fastest intervals. If you feel like they boost your performance, wear them on race day too! As the old saying goes, “any medicine that works is good medicine!” If you’re short on cash, though, you’re not missing out on much.
What should you look for when purchasing compression gear
One final note when it comes to shopping for compression socks: All of these studies used medical grade “compression stockings,” which are different from the knee-high Nike socks you might find at your local sporting gear store marketed as “compression wear.”
Medical grade compression socks are rated in millimeters of mercury or mmHg (an arcane unit, to be sure) at the ankle and calf. So a sock labeled 15-20 mmHg is 20 mmHg at the ankle and 15 at the calf.
For reference, studies 1, 2, and 3 used 18-22 mmHg, 18-24 mmHg, and 15-22 mmHg, respectively. For Ali’s 2011 study (4), “low” corresponded to 12-15 mmHg, “medium” to 18-21 mmHg, and “high” to 23-32 mmHg.
If you’re shopping for compression socks, I recommend something around 15-20 mmHg. If these numbers are a bit confusing, just remember that true compression stockings need to be sized by calf and ankle circumference, not simply by shoe size. Otherwise you won’t get the proper compression levels.
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