“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 ↗ Against passive rest, soreness was lower a day later (standardized mean difference −0.66) and still lower at three and four days. The authors rated the trials low in quality, and most did not actively watch for side effects.

A 2016 meta-analysis of 9 trials put soreness on a common 0–10 scale. Cold water beat passive recovery by 0.29 points right after exercise and 0.32 points later, and the authors estimated the best case at about a 5% reduction.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 ↗ Water between 10 and 15°C for 10 to 15 minutes did best, and 5–10°C water showed no significant effect on later soreness.

The largest review pooled 52 studies of physically active people. A day after high-intensity exercise, cold water had improved muscle power (SMD 0.22) and perceived recovery, and it had lowered both 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 ↗ Strength recovered no faster.

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 ↗ Against 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 ↗