Cold and heat exposure 03: Contrast therapy

Short answer. Contrast therapy beats doing nothing for soreness and strength loss, but in the reference meta-analysis it was not shown to beat simply picking one temperature, and all eighteen trials were at high risk of bias. What it does to training adaptation has not been studied.

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The question

Contrast water therapy alternates brief immersions in cold and warm water, typically cycles of one to three minutes each, with cold around 10 to 12°C and warm around 38 to 42°C (Hyldahl and Peake, 2020). The premise is that repeatedly constricting and dilating blood vessels creates a pumping action that flushes the tissue better than either temperature alone.

Two entries in this series look at what cold and heat each do on their own. (→ Cold and heat exposure 01; Cold and heat exposure 02; Cold and heat exposure sub-hub) This one asks a narrower question: is the combination worth the extra complexity?

What has been tested

One systematic review and meta-analysis remains the reference point. Eighteen controlled trials met inclusion, and the reviewers rated all eighteen as being at high risk of bias, which is the first thing to know about everything that follows.

Pooled data from thirteen studies found that contrast therapy produced greater improvement in muscle soreness than passive recovery at every follow-up point measured: under six hours, and at 24, 48, 72 and 96 hours. The pooled data also showed reduced loss of muscle strength against passive recovery at each of those same time points (Bieuzen et al., 2013).

Then the part that answers the question being asked. The same review compared contrast therapy against cold water immersion, warm water immersion, compression, active recovery and stretching. Across all of those comparisons, there was little evidence that any one intervention was superior. The reviewers concluded that contrast therapy beats passive recovery or rest, and that there is little difference in recovery outcome between contrast therapy and other popular recovery interventions.

So the effect is against doing nothing, not against doing something simpler. The extra complexity has not earned its keep in the comparison that would test it.

The reviewers also noted that the magnitude of these effects may be most relevant to elite sporting populations, which is a narrower claim than the one usually made for the same data.

What has not been tested

No meta-analysis has examined what regular contrast therapy does to training adaptations over a block of resistance training. Cold has one. Heat has a preliminary version. Contrast therapy, despite being at least as widely used, has nothing.

This matters more than it might sound, because the two components have been reported to push training adaptation in opposite directions, each by a small amount. Nobody has established whether alternating them cancels, compounds, or does something else entirely. That is not a hedge. It is the state of the question.

Where this leaves it

If the goal is feeling better tomorrow, contrast therapy works, on the same low-quality evidence base as its alternatives, and no better than picking one temperature.

If the goal is building muscle, you are combining an intervention with a small negative point estimate and one with a small positive point estimate, and the result of that combination is unstudied.

If the goal is choosing between recovery methods, the plain reading of the meta-analysis is that the choice between them matters less than the choice to do something at all. All of it rests on trials the reviewers themselves flagged as high risk of bias.