Hematological Adaptations to Post-Exercise Sauna Bathing With No Fluid Intake: A Randomized Cross-Over Study

ABSTRACT

Purpose: Sauna bathing is recommended to improve the sports training process, yet empirical evidence confirming its effectiveness is still inconclusive. We examined the effects of post-exercise sauna bathing on hematological adaptations and exercise capacity in healthy men. Methods: Thirteen physical education students participated in randomized cross-over study: two, 4-week interventions, with 10-week washout. The interventions involved 3 times per week 60-min stationary cycling either with 30-min of post-exercise sauna bathing (89 ± 3°C, 10 ± 2% RH) or without; no fluid was ingested during both exercise and sauna sessions. Before and after both interventions, participants were tested for total hemoglobin mass (tHb-mass), intravascular volumes, erythropoietin, ferritin, red blood cell parameters with reticulocyte fractions, along with maximal/peak and submaximal variables in a graded exercise test (GXT). Results: Regardless of intervention type, tHb-mass increased (p = .014) whereas ferritin concentration decreased (p = .027); however, changes in tHb-mass were within the range of typical error (<1.8%). Absolute and relative values of maximal power and power at gas exchange threshold, as well as peak oxygen uptake (all p < .010), also increased irrespective of intervention type. Conclusions: The use of post-exercise sauna bathing with fluid intake restrictions does not provide any additional benefits in tested variables over endurance training alone. Thus, further evidence is required before recommendations to utilize this post-exercise conditioning strategy are deemed valid.

KEYWORDS:

• Exercise capacity
• intravascular volumes
• red blood cell parameters
• total hemoglobin mass

Acknowledgments

The authors would like to thank Mr Blair T. Crewther, Ph.D., for critical comments on the manuscript, Mr Konrad Witek, Ph.D., and technicians of the Institute of Sport—NRI for blood sampling and analyses. We also thank the students of the State University of Applied Sciences in Nowy Sącz for their diligent participation in this research, and the university authorities for enabling us to conduct this research. The authors declare no conflicts of interest.

IRB Approval

The study was approved by an Ethics Committee at the Institute of Sport—NRI (Agreement number KEBN-17-33-DS).

Additional information

Funding

The study was conducted under project No. 102.15, financed by the Ministry of Science and Higher Education of the Republic of Poland, as part of the statutory activity of Institute of Sport—National Research Institute.