INTRODUCTION
Passive heating (PH) has been proposed as a potential exercise mimetic strategy showing acute and chronic effects on skeletal muscle adaptation in people who are unable to perform or complete sufficient exercise. Like exercise, heating increases heart rate (HR), peripheral arterial blood flow and provoke thermoregulatory response. The aim of our study was to evaluate the cardiovascular response in recovery after PH and to compare it with the recovery after HR and duration matched cycling (HMC).
METHODS
In a fixed crossover designed study, 9 healthy participants (23.6 ± 2.4 yr) underwent 30 min of whole body passive heating (55gradC in infrared sauna); followed by 30 min of manually load managed cycling on a separate day. Cycling load was added in steps to comply the same HR versus time profile as obtained during PH. HR (Polar) and sublingual temperature (Tsl) were measured continuously 25 minutes during recovery after PH and HMC. Values were compared at 5th and 25th minute after PH/HMC cessation. Heart rate recovery in 120 seconds after PH/HMC (HRR120) cessation was calculated.
RESULTS
HRR120 was statistical significantly greater after HMC compared to PE (24,6 ± 2,8 and 19,7 ± 1,3, respectively, p=0,048). On the other hand, 5 and 25 minutes after PH/HMC cessation HR did not differ statistically comparing PE and HMC. Tsl did not change after PH/HMC compared to rest and did not differ during recovery comparing values after both sessions.
CONCLUSIONS
Different HR recovery after PH compared to HMC indicates that different cardiac autonomic regulation mechanisms may control the acute cardiac adaptation to heat/exercise stress nevertheless the HR at the end of stress stimuli was the same. Further investigations like heart rate variability studies are needed to find the main differences in autonomic mechanisms underlying these differences.