Short read
Roberts and colleagues from the University of Queensland and partner institutions published two linked studies in The Journal of Physiology in 2015. The modality is cold water immersion after strength training, not sauna. In the training study, 21 physically active men did leg strength training on 2 days a week for 12 weeks. After each session they had either a 10-minute cold water bath at 10.1 degrees or 10 minutes of low-intensity cycling at around 60 watts. In the acute study, 9 active men did single-leg sessions followed by either condition, with muscle biopsies before and 2, 24 and 48 hours after.
Compared with the cold water group, the active recovery group gained more strength and muscle: isokinetic work increased by 19 %, the cross-sectional area of type II fibres by 17 % and the number of myonuclei per fibre by 26 %, and these gains appeared only with active recovery. In the acute study, satellite cells marked by NCAM rose by 10 to 30 % and those marked by Pax7 by 20 to 50 % at 24 to 48 hours after active recovery; after cold water, NCAM-positive cells rose only at 48 hours. The authors conclude that cold water immersion blunts the acute changes that drive muscle growth and that routine use after training should be reconsidered.
The samples are 21 and 9 men, legs only. The cold came directly after each session, so the study says nothing about a gap of several hours, about cold on rest days, about endurance training, women, older people or cold outside a training context. The comparison was light cycling, not doing nothing.
The condition is the finding: cold water immediately after strength training. Without it, a precise result becomes the false claim that cold is harmful in general.