Monday, August 8, 2011

How tight should your compression tights be?

from sweatscience.com

As the various brands of compression gear compete to distinguish themselves, one of the claims you hear a lot (I’m looking at you, CEP) is that you need “medical grade” compression to achieve true performance benefits. Seems reasonable. So let’s test it…

Australian researchers just published a new study in the International Journal of Sports Physiology and Performance, looking at the effect of wearing Skins tights on endurance running performance. The twist: their subjects (11 well-trained distance runners) did three sets of testing, once in loose shorts, once in the “right” size of Skins leggings, and once in a set a Skins leggings one size too small (to get extra compression). The correct size produced an average of 19.2 mmHg pressure gradient across the calf, while the smaller size produced 21.7 mmHg. For comparison, CEP’s socks promise a max of 22-24 mmHg at the ankle, with 18-20 mmHg on the calf.

The researchers tested pretty much every parameter they could think of, and then some. The performance parameters were simple: a progressive VO2max test, and a time-to-exhaustion test at 90% of VO2max. The physiology measures included heart rate, blood lactate, expired gases, and near-infrared spectroscopy of the leg muscles to measure how much oxygen-carrying hemoglobin and non-oxygen-carrying hemoglobin was passing by in the blood.

The results: in a nutshell, actual running performance was unchanged in any way. Compression tights didn’t make the runners run faster, and there was no difference between the two levels of compression. Repeat:

No improvement in endurance running performance was observed in either compression condition.

But… they measured all these lovely physiological parameters. And sure enough, after sifting through all of them, it turns out that they weren’t all identical. At low speeds, compression garments seemed to increase muscle blood flow; at high speeds they increased non-oxygen-carrying hemoglobin in the vastus medialis; etc. etc. The picture is pretty messy, but the message is still clear:

However, the magnitude of this improved venous flow through peripheral muscles appears trivial for athletes and coaches, as it did not improve [time-to-exhaustion] performance. This would suggest that any improvement in the clearance of waste products is insufficient to negate the development of fatigue.

But all is not lost for compression fans:

However, the data presented may have helped to identify and support the responsible mechanisms that relate to the postexercise recovery improvements associated with wearing [lower-body compression garments].

Note that this study didn’t actually find anything involving improved recovery. It just found that if you squeeze a limb, blood flow through that limb changes. That might result in improved recovery (and indeed some other studies do suggest that’s the case), or it might not. But the idea that compression will help you run faster is seeming less and less plausible.

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