I am often asked by my massage clients what massage is doing to their muscles. One of their common misconceptions, especially when they have recently over-exercised and their muscles are sore, is that it is removing lactic acid from their muscles. However, it has been known for a few years that lactic acid, a by product of anaerobic exertion, actually is converted back to pyruvate pretty quickly once exercise ends and oxygen again becomes available to the cells. In fact, massage right after exercise actually decreases blood flow and lactic acid removal (see this summary in the New York Times wellness blog, and if you are really curious, follow the link in the article to the one about boxing).
So what is actually causing post-exercise muscle pain and how might massage help? A 2006 Scientific American review here explains delayed-onset-muscle soreness (or DOMS) succinctly, and this Wikipedia article brings the information bit more up-to-date. Both articles say that DOMS is not completely understood, but that it’s clear that lactic acid does not play much, if any, role. Instead, micro-tears within the muscle fibers and connective tissue, followed by inflammation (which takes a while, explaining the delay), are the current explanation for what causes the pain. And a new study, published in February, 2012, and summarized here, indicates that massage shortly after the event helps minimize this inflammation, while also promoting the production of new mitochondria (the energy machines of cells).
On the other hand, it isn’t even known if inflammation is what causes post-exercise soreness. A recent article by Radak et al. suggests that nitric oxide may be the culprit. So, until we have a more definitive answer about what causes the soreness, the real question may be: does massage after exercise help with DOMS? Many sports enthusiasts argue that it does. I remember working a long-distance relay a couple of years back, and a physical therapist told me that she recovered much faster after such running events if she got massage within the hour.
And there is research to back her claim (although results are not clear-cut) primarily by decreasing pain levels and swelling about 30% (see Zainuddin et al and this review by Torres et al.). This and other studies say it does not help with another post-exercise problem – decreased muscle function, although the Torres review concludes that massage helps with pain and also helps with loss of function more than ice, stretching or low-intensity exercise. Torres et al. conclude that this massage effect is not enough to be clinically significant, but 30% less pain sounds a lot better than nothing to me, especially since new research says we shouldn’t just pop painkillers after exercise, because they have a deleterious effect on our recovery.
Beyond this, some of the most interesting research from my perspective has been published on rabbits (this study, for example, show a dose-dependent effect because more compressions a la sports massage meant faster recovery for the rabbits, while this one showed increased muscle elasticity with a machine massage meant to emulate deep effluerrage (those long smooth strokes we all love)). And massage is also used after exercise on horses, something I doubt equine owners would pay for unless it really did help the horse perform better.
Of course, there are other reasons than ameliorating DOMS for having a massage. But please don’t think that it is removing lactic acid. It isn’t there in the first place to be removed.
Disclaimer: As always, research on massage is still in its infancy. Most studies of its effects are too small to have confidence in their results, until they are duplicated. That includes everything cited here.