Heat eases sore muscles as well as ice does

Delayed onset muscle soreness, the ache that peaks a day or two after hard or unfamiliar exercise, is one of the most common reasons people skip the next session. Ice baths have become the fashionable answer, while heat is often dismissed as the old-fashioned option. Trials on both are scattered and small, and few people know whether either genuinely reduces soreness or when to apply them. This review pooled the randomised evidence on heat and cold to find out.

The authors followed a preregistered protocol and searched nine databases up to December 2020 for randomised controlled trials of heat or cold therapy for delayed onset muscle soreness. Thirty-two trials involving 1098 people were included and combined in a pooled analysis. Pain was assessed within 24 hours of exercise and beyond 24 hours. The analyses separated cold water immersion from other cold therapies, and hot packs from other forms of heat.

Cold therapy applied within an hour of exercise reduced pain within the first 24 hours, with cold water immersion showing a significant effect, but had no clear effect beyond 24 hours. Heat reduced pain both within and beyond 24 hours, and hot packs showed the largest effects of any approach in both time windows. Other heat therapies were not statistically significant. When cold and heat were compared directly, there was no significant difference between them.

This pooled analysis pushes back on the idea that cold is the only serious recovery tool: heat performed at least as well, and hot packs posted the biggest effects. It also sharpens the timing question, since benefits were tied to application within an hour of finishing exercise. The trials varied in methods and quality, and the authors call for higher-quality studies to settle whether heat or cold truly works better. The comparison covers soreness only, not muscle adaptation or performance.

If post-exercise soreness is what you want to blunt, this is evidence that both a hot pack and a cold soak can help, and that the humble hot pack is not the inferior choice. Timing appears to matter, with the benefit tied to applying either therapy within an hour of finishing. Cold's advantage faded after the first 24 hours, while heat kept helping beyond it. There is no basis here for treating ice as obligatory.