Researchers led by Dr. Llion Roberts ran two linked experiments. In the first, 21 physically active men did strength training twice a week for 12 weeks. After every session they either sat in cold water for 10 minutes or did light active recovery.

In the second, nine active men did one bout of single-leg strength exercises. Muscle biopsies were taken before the session and again 2, 24 and 48 hours later.

Active recovery beat the cold dip on both strength and muscle mass (P < 0.05, the usual cutoff for “unlikely to be chance alone”).

Muscle grows when training damage triggers repair signals. Satellite cells, the muscle’s stem cells, help add new material to fibers. A pathway called mTORC1 switches on protein building.

One proposal is that cold narrows blood vessels and dampens that response. In Roberts’ second experiment, cold immersion blunted the short-term changes in satellite cells and in enzymes that regulate growth.

Researchers still describe the exact mechanism as unsettled, so treat this as a working explanation, not a proven chain of events.

A 2024 meta-analysis in the European Journal of Sport Science pooled 8 trials that paired resistance training with post-exercise cold water immersion. Sessions ran two to three times a week, and four trials used trained lifters.

The pooled effect favored training without cold water: −0.22 (95% credible interval −0.47 to 0.04). The interval touches zero, so this is a likelihood, not a certainty. The authors put the probability that cold immersion reduced growth at about 96%.

Training status did not clearly change the picture. The authors’ meta-regression found no clear difference between trained and untrained lifters.

Strength gives a murkier picture. A 2022 meta-analysis of 10 trials (170 participants, 92% male) found cold immersion trimmed strength gains, with an effect of −0.23 (95% CI −0.45 to −0.01). Whole-body immersion showed no significant difference.

That echoes Fyfe’s 2019 trial, where fiber growth shrank but leg press gains held steady.

The newest network meta-analysis (2026, 87 studies, 2,313 participants) did not report muscle size outcomes. For strength, passive recovery ranked highest, and medium-length, moderate-temperature cold immersion did not differ from it.

A 2022 review of 52 randomized trials (1,191 adults), summarized by American Family Physician in 2025, found that cold immersion after hard exercise may improve perceived recovery and delay soreness over the next 24 hours. Dips under roughly 10 to 15 minutes in water below 59°F (15°C) were most consistent.

A separate 2023 meta-analysis of 20 studies in Frontiers in Physiology was less generous. Soreness was lower right after exercise, but not significantly lower at 24 or 48 hours once a random-effects model was applied.

Most of those trials carried high or unclear risk of bias, and only five used random allocation.

First, the effect size is small. A value near −0.2 is conventionally labeled small, and the 2024 interval touches zero. Cold water probably costs some growth, but not a lot.

Second, the samples are small and young. Roberts had 21 men and Fyfe had 16. The 2022 strength review was 92% male, and the 2026 network analysis was about 85% male, so results may not apply equally to women or older adults.

Third, the trials are short. The two training trials covered here ran 7 and 12 weeks. Long-term adaptations are listed as an evidence gap in the 2026 review.

Fourth, timing is barely tested. The pooled trials started cold exposure soon after training. ACSM suggests waiting 4 to 6 hours but notes that few studies have examined it.