title: Haemodynamic responses to dehydration in the resting and exercising human leg.
abstract: Dehydration and hyperthermia reduces leg blood flow (LBF), cardiac output ([Formula: see text]) and arterial pressure during whole-body exercise. It is unknown whether the reductions in blood flow are associated with dehydration-induced alterations in arterial blood oxygen content (C aO2) and O2-dependent signalling. This study investigated the impact of dehydration and concomitant alterations in C aO2 upon LBF and [Formula: see text]. Haemodynamics, arterial and femoral venous blood parameters and plasma [ATP] were measured at rest and during one-legged knee-extensor exercise in 7 males in four conditions: (1) control, (2) mild dehydration, (3) moderate dehydration, and (4) rehydration. Relative to control, C aO2 and LBF increased with dehydration at rest and during exercise (C aO2: from 199 ± 1 to 208 ± 2, and 202 ± 2 to 210 ± 2 ml L(-1) and LBF: from 0.38 ± 0.04 to 0.77 ± 0.09, and 1.64 ± 0.09 to 1.88 ± 0.1 L min(-1), respectively). Similarly, [Formula: see text] was unchanged or increased with dehydration at rest and during exercise, whereas arterial and leg perfusion pressures declined. Following rehydration, C aO2 declined (to 193 ± 2 mL L(-1)) but LBF remained elevated. Alterations in LBF were unrelated to C aO2 (r (2) = 0.13-0.27, P = 0.48-0.64) and plasma [ATP]. These findings suggest dehydration and concomitant alterations in C aO2 do not compromise LBF despite reductions in plasma [ATP]. While an additive or synergistic effect cannot be excluded, reductions in LBF during exercise with dehydration may not necessarily be associated with alterations in C aO2 and/or intravascular [ATP].
authors.affiliation: Centre for Sports Medicine and Human Performance, Brunel University, Uxbridge, Middlesex, UB8 3PH, UK.
authors.forename: James
authors.initials: J
authors.lastname: Pearson
authors.forename: Kameljit K
authors.initials: KK
authors.lastname: Kalsi
authors.forename: Eric J
authors.initials: EJ
authors.lastname: Stöhr
authors.forename: David A
authors.initials: DA
authors.lastname: Low
authors.forename: Horace
authors.initials: H
authors.lastname: Barker
authors.forename: Leena
authors.initials: L
authors.lastname: Ali
authors.forename: José
authors.initials: J
authors.lastname: González-Alonso
mesh_terms: D000255:Adenosine Triphosphate / Q000097:blood; D016022:Case-Control Studies; D003681:Dehydration / Q000097:blood*; D015444:Exercise; D006439:Hemodynamics; D006801:Humans; D007866:Leg / Q000098:blood supply / Q000502:physiology*; D008297:Male; D010100:Oxygen / Q000097:blood; D012039:Regional Blood Flow; D012146:Rest; D055815:Young Adult
chemical_list: D000255:Adenosine Triphosphate; D010100:Oxygen