Short read
Ahokas and colleagues from the University of Jyväskylä and Mid Sweden University published this systematic review in Sports Medicine - Open in 2025. The search ran in December 2023 and was updated in June 2025. Included were randomised or crossover trials comparing whole-body heat from 36 degrees upwards after training, delivered by Finnish sauna or hot water immersion, with passive or placebo recovery. Sauna and hot water are pooled. The 14 trials had 194 participants aged 15 to 60, 9 on acute recovery and 5 on training adaptation.
For acute recovery, soreness was measured in 3 trials, and just 1 of them found relief compared with passive recovery; and creatine kinase showed minimal or no effect. Countermovement jump height recovered faster in some trials, from right after the heat up to 38 hours later, while squat jump and sprint showed no consistent advantage. Overall, 4 trials found no effect, 4 a benefit and 1 a disadvantage. For adaptation, 2 of 5 trials found better running performance than their control conditions, at least in the heat, and others found no effect on cycling performance or VO2max.
Groups were small, with 6 to 20 people each, and 11 of the 14 trials included men only. Heat protocols, exercise types and time points differed so much that no meta-analysis was possible, so each finding rests on one or two trials. 3 trials carried a high risk of bias, 11 some concerns, and 1 was prospectively registered.
The recovery claim is thinner than the adaptation claim: less soreness rests on one of three trials, while jump height did come back faster in some of them. None of this can be assigned to sauna alone.