Influence of a Negative Hydrostatic Column and Central Fluid Shift via ‐6° Head‐down Tilt Posture on Cardiovascular Performance

Abstract

AimsTo examine the influence of a negative hydrostatic column via ‐6° head‐down tilt (HDT) exercise on cardiovascular performance and to determine if the HDT posture stimulates greater cardiovascular adaptations during exercise training compared to upright (UPR).Methods9 males (21±2 yrs) performed VO2peak cycle exercise tests in the UPR, supine (SUP), and HDT positions. 9 different males (20±2 yrs) were endurance trained on a cycle ergometer in the UPR position for 8 wks (UPRTN) or in the UPR position for 4 wks followed by 4 wks in the HDT position (HDTTN).ResultsDuring acute exercise, VO2peak was decreased in the SUP and HDT positions compared to the UPR (2.01±0.46, 2.01±0.51 vs. 2.32±0.61 L/min respectively, P < 0.05). Stroke volume (SV) at 100 watts was greater in the HDT position compared to the UPR (77±5 vs 71±4 ml/beat, P < 0.05). Following training SV at 100 watts increased from 77±1 to 85±9 ml/beat in the HDTTN group during UPR exercise (P < 0.05). In addition, SV increased from 76±10 to 85±16 ml/beat in the HDT position for the same individuals (P < 0.05). SV in the UPRTN during 100 watts in the HDT position was unchanged but increased during UPR exercise following 8wks of training (65±3 to 75±5 ml/beat, P = 0.21).ConclusionsHDT exercise increases sub‐maximal SV compared to UPR exercise. Training in the HDT position induces cardiovascular adaptations in both UPR and HDT exercise that are not achieved with UPR training.