“Ice baths help you recover faster after exercise.”

The research found this

The 2012 Cochrane review pooled 17 small trials with 366 participants who sat in water colder than 15°C after exercise.1Source 1 · Systematic reviewCold-water immersion (cryotherapy) for preventing and treating muscle soreness after exerciseBleakley C, McDonough S, Gardner E, et al.. Cochrane Database of Systematic Reviews, 2012.Read the paper ↗PubMed ↗ Compared with passive rest, cold water left people less sore a day later (a standardized effect size of −0.55) and two days later (−0.66), and they were still less sore at three and four days. The authors rated the trials low in quality, and most of the trials made no active effort to watch for side effects.

A 2016 analysis pooled 9 trials and converted their soreness ratings to a common 0–10 scale. Cold water beat passive recovery by 0.29 points right after exercise and 0.32 points later.2Source 2 · Meta-analysisCan Water Temperature and Immersion Time Influence the Effect of Cold Water Immersion on Muscle Soreness? A Systematic Review and Meta-AnalysisMachado AF, Ferreira PH, Micheletti JK, et al.. Sports Medicine, 2016.Read the paper ↗PubMed ↗ The authors estimated the best case at about a 5% reduction. Water between 10 and 15°C for 10 to 15 minutes did best, and the colder 5–10°C water showed no significant effect on later soreness.

The largest review pooled 52 studies of physically active people and found no faster recovery of strength. A day after high-intensity exercise, though, cold water had improved muscle power (an effect size of 0.22) and how recovered people felt. It had also lowered soreness and creatine kinase (a blood marker of muscle damage).3Source 3 · Meta-analysisImpact of Cold-Water Immersion Compared with Passive Recovery Following a Single Bout of Strenuous Exercise on Athletic Performance in Physically Active Participants: A Systematic Review with Meta-analysis and Meta-regressionMoore E, Fuller JT, Buckley JD, et al.. Sports Medicine, 2022.Read the paper ↗PubMed ↗

Timing matters if you compete again the same day. A 2022 review of 68 studies found cold water impaired sprint performance an hour later and jump performance six hours later, although jumps were better by 24 hours.4Source 4 · Meta-analysisThe effect of cold water immersion on the recovery of physical performance revisited: A systematic review with meta-analysisChoo HC, Lee M, Yeo V, et al.. Journal of Sports Sciences, 2022.Read the paper ↗PubMed ↗ Compared with other recovery methods, cold water came out ahead for soreness in a 2023 review of 28 studies, and cold-air cryotherapy did better for strength.5Source 5 · Meta-analysisEffects of Cold-Water Immersion Compared with Other Recovery Modalities on Athletic Performance Following Acute Strenuous Exercise in Physically Active Participants: A Systematic Review, Meta-Analysis, and Meta-RegressionMoore E, Fuller JT, Bellenger CR, et al.. Sports Medicine, 2023.Read the paper ↗PubMed ↗