Pulmonary O-2 uptake during exercise: Conflating muscular and cardiovascular responses

Whipp, B.J., Ward, S. and Rossiter, H.B. (2005) Pulmonary O-2 uptake during exercise: Conflating muscular and cardiovascular responses. Medicine and Science in Sports and Exercise, 37, pp. 1574-1585. (doi: 10.1249/01.mss.0000177476.63356.22)

Abstract

For moderate-intensity exercise (below lactate threshold, θL), muscle O2 consumption (Q̇O2) kinetics are expressed in a first-order phase 2 (or fundamental) pulmonary O2 uptake (V̇O2) response: dV̇O2/dt · τ + ΔV̇O2(t) = ΔV̇O2(ss); where ΔV̇O2(ss) is the steady-state V̇O2 increment, and τ the V̇O2 time constant (which is within approximately 10% of τQ̇O2). A likely source of Q̇O2 control in this intensity domain is ADP-mediated, for which intramuscular phosphocreatine (PCr) may serve as a proxy variable. Whether, in reality, this behavior reflects the operation of a single homogeneous compartment is unclear, however; a multicompartment structure comprised of units having a similar ΔV̇O2(ss) but with widely varying τ can also yield a well-fit exponential response with an apparent single τ. In support of this is the inverse (although poorly predictive) correlation between τ and both θL and V̇O2max. Above θL, the fundamental V̇O2 kinetics are supplemented with a delayed, slowly developing component that can set V̇O2 on a trajectory towards V̇O2max, and that has complex temporal- and intensity-related kinetics. This V̇O2 slow component is also demonstrable in [PCr], suggesting that the decreased efficiency above θL predominantly reflects a high phosphate cost of force production rather than a high O2 cost of phosphate production. In addition, the oxygen deficit for the slow component is more likely to reflect a progressive shifting of ΔV̇O2(ss) rather than a single ΔV̇O2(ss) having a single τ.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: UNSPECIFIED
• Authors: Whipp, B.J., Ward, S., and Rossiter, H.B.
• College/School: College of Medical Veterinary and Life Sciences
• Journal Name: Medicine and Science in Sports and Exercise