In the past month, we have examined the use of ice baths for runners and heating before running in treating injury and preventing soreness. Today, we’re taking on contrast therapy, a more recent take on water immersion for athletes.
Contrast therapy consists of immersing your legs in alternating containers of warm and cold water for several cycles over a 20-30 minute period. It’s much more labor-intensive than a simple ice bath, since it requires substantial set-up time and a good bit of work to ensure that both water containers are at the proper temperature. Nevertheless, it isn’t too much trouble to improvise a contrast bath setup at home for your foot or lower leg, so if there is some therapeutic benefit, even recreational runners might be interested.
As usual, before you spend the time and effort, we’ll look to the scientific literature to see if contrast therapy is worth the trouble.
The science of contrast baths
Contrast bath and muscle temperature
Contrast therapy seems to have emerged as a treatment option for mild muscle strains and post-exercise muscle soreness in the late ‘90s, when several studies cropped up investigating its effects. Initially, the benefits were purported to be a result of changes in intramuscular temperatures. The repeated heating and cooling warmed, then cooled the muscles of the legs, facilitating recovery.
A pair of studies published in 1994 and 1997 by William Myer and colleagues at Brigham Young University investigated this claim using needle-mounted thermometers placed just under the skin and 1 cm deep into the calf muscle. In both studies the subjects underwent a 20-minute contrast routine, starting with heat and alternating with cold every four minutes. The 1994 study used two whirlpool baths, while the 1997 study used hot packs and ice bags.
In both cases, Myer et al. found that, while the contrast therapy caused fluctuations in skin temperature, muscular temperatures did not change significantly during the contrast therapy.
The body likely was able to divert blood flow so that the deep muscle temperature was maintained at a fairly constant level. Having this assumption about contrast therapy overturned forced researches to look for other possible mechanisms.
Contrast bath and recovery
While some studies have shown that contrast therapy produces better recovery and reduces muscle swelling after intense exercise vs. passive recovery (i.e. doing nothing), only a few studies have compared contrast therapy to more simple forms of immersion therapy, like taking an ice bath. These studies have all found a benefit for both types of immersion over passive recovery, but no difference between the two.
In a review on immersion therapy in general, Ian Wilcock, John Cronin, and Wayne Hing suggest that most of the benefits of contrast therapy are from the hydrostatic pressure from the water, not the variations in temperature.3 If this is the case, a complicated contrast setup is no better than a cold bathtub, or indeed even a dip in a lukewarm swimming pool or lake!
Contrast bath and blood flow
Some researchers, however, still tout the benefits of the contrasting cold and hot temperatures. Darryl Cochrane at Massey University in New Zealand proposes that contrast therapy might work via a “muscle pumping” action, where the alternating temperatures result in a series of blood vessel constrictions and dilations, mimicking the muscle pumping that occurs during light aerobic activity.
One of the reasons it’s important to do a cool-down after a hard workout or race is that the contraction and extension of your muscles results in a pump-like action in your blood vessels, which moves metabolic waste products out of your muscles and back into the bloodstream. If this is the case, contract therapy could be useful in accelerating recovery after a hard effort, especially if you don’t or can’t do some light, aerobic “active recovery.” After a marathon, for example, going out for a 20-30min jog is probably the last thing you want to do. Setting up a contrast bath station could be an attractive way to flush out waste after a tough race.
How to make your own contrast bath
Since there is relatively little research on the practical applications of contrast therapy, there are not clear guidelines on what a “proper” contrast setup consists of. Here is what we do know from the research:
- Most studies alternate between water temperatures of 45-68° F for the cold water and 93-106° F for the hot water.
- Each immersion lasts between 3-5 minutes and the total immersion time is between 20 and 30 minutes.
- Some studies end with heat, and others end with cold. The prevailing opinion now seems to be that it’s best to end on the cold bath, since that should retard inflammation.
Contrast baths have perhaps the least scientific backing out of the three immersion techniques we’ve looked at. Cold water immersion has the strongest, having been demonstrated as a good way to reduce muscle soreness after a strenuous workout. Hot water immersion has its uses too, but carries the risk of promoting inflammation and swelling.
Contrast therapy’s role seems to be limited to replacing or supplementing active recovery (like jogging or walking) after a hard workout or race. It’s a complicated operation to set up, seeing as you need large containers of both hot and cold water. So, like many of the fads in exercise physiology, you probably aren’t missing out on much if you skip on contrast baths. However, you don’t really have anything to lose if you’ve got the time and will to try it, and you may find it has its use in your own training and recovery.
