Post-Exercise Passive Heating Strategies with Hot Water Immersion and Sauna Suits Improve VO2max, Running Economy, and Lactate Threshold

Aim: The purpose of this study was to examine the effects of post-exercise passive heating strategies (sauna suit and hot water immersion) on VO2max, economy, and lactate threshold. Methods: Following recruitment, participants were randomized into one of three groups: 1) exercise training alone – control (N=10), 2) exercise training with post-exercise hot water immersion (N=10), and exercise training with post-exercise sauna suit (N=10). At baseline and post-program participants completed a running economy protocol and maximal exercise testing protocol to measure VO2max and lactate threshold. The running economy protocol consisted of three consecutive 5-minute stages: stage 1 = 4.6 mph, stage 2 = 5.0 mph, and stage 3 = 5.4 mph. Ventilatory thresholds (VT1 and VT2) were also obtained during the maximal exercise testing protocols. The running economy and maximal exercise testing protocols were performed two times (at both baseline and post-program) to quantify the biological variability of VO2max, economy, and lactate threshold. Results: After 3wk, mean VO2max changes in the sauna suit and hot water immersion groups were significantly greater (p < 0.05) when compared to the control group. Similarly, following the 3wk intervention, lactate threshold changes in the sauna suit and hot water immersion groups were significantly more favorable (p < 0.05) when compared to the control group. In the hot water immersion group, there were significant within-group improvements (p < 0.05) in economy between baseline and 3wk for all three stages. In the control group, 50% (4/8) of individuals were categorized as responders (change in VO2max (Δ > 3.2%)) and 50% (4/8) were categorized as non-responders (Δ ≤ 3.2%). In the hot water immersion and sauna suit groups, the incidence of VO2max responders were significantly (p < 0.05) greater when compared to the control group. In fact, there were 100% VO2max training responsiveness (7/7 and 9/9) in the hot water immersion and sauna suit groups, respectively. Conclusions: Both post-exercise passive heating strategies were equally effective at increasing VO2max and lactate threshold values. In addition, post-exercise hot water immersion was a more effective strategy at improving running economy relative to wearing a sauna suit after exercise.