Ice baths after lifting shown to slow growth

Soaking in icy water after lifting weights can result in less muscle growth than doing nothing to recover, according to a cautionary new study of young men and their muscles.

For the new study, which was published in September in the Journal of Applied Physiology, scientists from Deakin University in Melbourne, Australia; Victoria University, also in Melbourne; and other institutions tested 16 healthy male volunteers’ muscular strength and their body composition and then divided them into two groups.

Both groups started a fullbody, progressive, resistance-training routine: standard bench presses, curls, pulldowns and so on, the weights increasing over time. Before and after the first session, the scientists biopsied a muscle in the men’s legs. The volunteers then worked out three times a week for seven weeks.

After each session, half the men recovered by sitting quietly in a room at the gym for 15 minutes. The others eased themselves into cold baths for 15 minutes after every workout, the water cooled to about 50 degrees Fahrenheit.

After the final workout, the scientists again biopsied muscles and rechecked leg strength and body composition. Then they examined the tissues microscopically.

All of the men developed larger muscle fibers, but the increase was much greater among those who sat than those who soaked.

The cold soakers also showed a different balance of certain biochemicals inside their muscles. In particular, their muscles contained less of a protein known to spark tissue growth and more of a different protein involved in tissue breakdown. In effect, the soakers’ muscles seemed to have become biochemically primed for slower recovery and less growth, said researcher Aaron Petersen.

Petersen and his colleagues suspect repeated cold-water immersions triggered complex metabolic reactions that prioritize keeping tissues warm over helping them to grow. But that theory needs to be studied in future experiments.