A new study has the answer.
The science:
For two weeks, researchers in the Netherlands put 12 healthy young men through a strength session every day. Post-workout, they put one leg in cold water and the other in lukewarm water for 20 minutes.
The results show that protein synthesis rates were significantly lower in the legs treated with cold water therapy. This indicates that the ritual may keep you from gaining strength. The researchers expect the results to hold for women, too.
Expert insight:
Protein synthesis helps you build muscle post-workout, explains study author Cas Fuchs, Ph.D. candidate in human biology at Maastricht University. Because of their low temperatures, ice baths reduce blood flow and amino acid presence in the muscles, both of which are necessary for the process to take place.
The bottom line:
When you’re on a strength-focused plan, Fuchs advises focusing your recovery efforts on protein intake and sleep rather than cold water therapy.