Exercise Heat Acclimation With Dehydration Does Not Affect Vascular and Cardiac Volumes or Systemic Hemodynamics During Endurance Exercise

Gavin Travers; José González-Alonso; Nathan Riding; David Nichols; Anthony Shaw; Julien D Périard

doi:10.3389/fphys.2021.740121

Exercise Heat Acclimation With Dehydration Does Not Affect Vascular and Cardiac Volumes or Systemic Hemodynamics During Endurance Exercise

Front Physiol. 2021 Nov 12:12:740121. doi: 10.3389/fphys.2021.740121. eCollection 2021.

Authors

Gavin Travers^{1

2}, José González-Alonso^{2

3}, Nathan Riding¹, David Nichols⁴, Anthony Shaw¹, Julien D Périard^{1

5}

Affiliations

¹ Athlete Health and Performance Research Centre, Aspetar Orthopaedic and Sports Medicine Hospital, Doha, Qatar.
² Centre for Human Performance and Rehabilitation, College of Health, Medicine and Life Sciences, Brunel University London, Uxbridge, United Kingdom.
³ Division of Sport, Health and Exercise Sciences, Department of Life Sciences, College of Health, Medicine and Life Sciences, Brunel University London, Uxbridge, United Kingdom.
⁴ Sport Development Centre, Loughborough University, Loughborough, United Kingdom.
⁵ Research Institute for Sport and Exercise, University of Canberra, Bruce, ACT, Australia.

Abstract

Permissive dehydration during exercise heat acclimation (HA) may enhance hematological and cardiovascular adaptations and thus acute responses to prolonged exercise. However, the independent role of permissive dehydration on vascular and cardiac volumes, ventricular-arterial (VA) coupling and systemic hemodynamics has not been systematically investigated. Seven males completed two 10-day exercise HA interventions with controlled heart rate (HR) where euhydration was maintained or permissive dehydration (-2.9 ± 0.5% body mass) occurred. Two experimental trials were conducted before and after each HA intervention where euhydration was maintained (-0.5 ± 0.4%) or dehydration was induced (-3.6 ± 0.6%) via prescribed fluid intakes. Rectal (T_re) and skin temperatures, HR, blood (BV) and left ventricular (LV) volumes, and systemic hemodynamics were measured at rest and during bouts of semi-recumbent cycling (55% V̇O₂ _peak) in 33°C at 20, 100, and 180 min. Throughout HA sweat rate (12 ± 9%) and power output (18 ± 7 W) increased (P < 0.05), whereas T_re was 38.4 ± 0.2°C during the 75 min of HR controlled exercise (P = 1.00). Neither HA intervention altered resting and euhydrated exercising T_re, BV, LV diastolic and systolic volumes, systemic hemodynamics, and VA coupling (P > 0.05). Furthermore, the thermal and cardiovascular strain during exercise with acute dehydration post-HA was not influenced by HA hydration strategy. Instead, elevations in T_re and HR and reductions in BV and cardiac output matched pre-HA levels (P > 0.05). These findings indicate that permissive dehydration during exercise HA with controlled HR and maintained thermal stimulus does not affect hematological or cardiovascular responses during acute endurance exercise under moderate heat stress with maintained euhydration or moderate dehydration.

Keywords: blood volume; heat acclimatization; heat stress; plasma volume; stroke volume.