The influence of metabolic and circulatory heterogeneity on the expression of pulmonary oxygen uptake kinetics in humans

What is the central question of this study? The finding that pulmonary oxygen uptake ( V̇O2p ) kinetics on transition to moderate exercise is invariant and exponential is consistent with a first‐order reaction controlling V̇O2p . However, slowed V̇O2 kinetics when initiating exercise from raised baseline intensities challenges this notion. What is the main finding and its importance? Here, we demonstrate how a first‐order system can respond with non‐first‐order response dynamics. Data suggest that progressive recruitment of muscle fibre populations having progressively lower mitochondrial density and slower microvascular blood flow kinetics can unify the seemingly contradictory evidence for the control of V̇O2p on transition to exercise.

[1]  A. Vanhatalo,et al.  Elevated baseline VO2 per se does not slow O2 uptake kinetics during work-to-work exercise transitions. , 2010, Journal of applied physiology.

[2]  H. Rossiter,et al.  Skeletal muscle $$ \dot{V} {\text{O}_2}$$ kinetics from cardio-pulmonary measurements: assessing distortions through O2 transport by means of stochastic work-rate signals and circulatory modelling , 2013, European Journal of Applied Physiology.

[3]  D. Poole,et al.  Muscle O2 uptake kinetics in humans: implications for metabolic control. , 1996, Journal of applied physiology.

[4]  B. Whipp,et al.  A new method for detecting anaerobic threshold by gas exchange. , 1986, Journal of applied physiology.

[5]  Effect of moderate-intensity work rate increment on phase II τVO2, functional gain and Δ[HHb] , 2013, European Journal of Applied Physiology.

[6]  P. Krustrup,et al.  Muscular and pulmonary O2 uptake kinetics during moderate‐ and high‐intensity sub‐maximal knee‐extensor exercise in humans , 2009, The Journal of physiology.

[7]  D. Paterson,et al.  Kinetics of O2 uptake, leg blood flow, and muscle deoxygenation are slowed in the upper compared with lower region of the moderate-intensity exercise domain. , 2005, Journal of applied physiology.

[8]  D. Poole,et al.  Control of microvascular oxygen pressures in rat muscles comprised of different fibre types , 2005, The Journal of physiology.

[9]  J. Spudich,et al.  ATP-dependent movement of myosin in vitro: characterization of a quantitative assay , 1984, The Journal of cell biology.

[10]  H. Rossiter,et al.  Slowed muscle oxygen uptake kinetics with raised metabolism are not dependent on blood flow or recruitment dynamics , 2014, The Journal of physiology.

[11]  T. Barstow,et al.  O2 uptake kinetics during exercise at peak O2 uptake. , 2003, Journal of applied physiology.

[12]  S. Ward,et al.  Effect of interbreath fluctuations on characterizing exercise gas exchange kinetics. , 1987, Journal of applied physiology.

[13]  R. Robergs.  A Critical Review of the History of Low- to Moderate-Intensity Steady-State VO2 Kinetics , 2014, Sports Medicine.

[14]  D. Poole,et al.  Oxygen Exchange Profile in Rat Muscles of Contrasting Fibre Types , 2003, The Journal of physiology.

[15]  S. Ward,et al.  Parameters of ventilatory and gas exchange dynamics during exercise. , 1982, Journal of applied physiology: respiratory, environmental and exercise physiology.

[16]  R. A. Howlett,et al.  Kinetic control of oxygen consumption during contractions in self‐perfused skeletal muscle , 2011, The Journal of physiology.

[17]  D. Paterson,et al.  High-intensity interval training speeds the adjustment of pulmonary O2 uptake, but not muscle deoxygenation, during moderate-intensity exercise transitions initiated from low and elevated baseline metabolic rates. , 2013, Journal of applied physiology.

[18]  T. Barstow,et al.  Linear and nonlinear characteristics of oxygen uptake kinetics during heavy exercise. , 1991, Journal of applied physiology.

[19]  Bruno Grassi,et al.  Skeletal Muscle Fatigue and Decreased Efficiency: Two Sides of the Same Coin? , 2015, Exercise and sport sciences reviews.

[20]  H. Rossiter,et al.  Effect of prior metabolic rate on the kinetics of oxygen uptake during moderate-intensity exercise , 2001, European Journal of Applied Physiology.

[21]  H. Rossiter,et al.  Skeletal muscle fatigue precedes the slow component of oxygen uptake kinetics during exercise in humans , 2011, The Journal of physiology.

[22]  D. Paterson,et al.  Pulmonary O2 uptake and muscle deoxygenation kinetics are slowed in the upper compared with lower region of the moderate-intensity exercise domain in older men , 2011, European Journal of Applied Physiology.

[23]  B J Whipp,et al.  Modulation of muscle and pulmonary O2 uptakes by circulatory dynamics during exercise. , 1990, Journal of applied physiology.

[24]  R. Hughson,et al.  Delayed kinetics of respiratory gas exchange in the transition from prior exercise. , 1982, Journal of applied physiology: respiratory, environmental and exercise physiology.

[25]  D. Paterson,et al.  The Critical Role of O2 Provision in the Dynamic Adjustment of Oxidative Phosphorylation , 2014, Exercise and sport sciences reviews.

[26]  H. Rossiter,et al.  A raised metabolic rate slows pulmonary O2 uptake kinetics on transition to moderate‐intensity exercise in humans independently of work rate , 2011, Experimental physiology.

[27]  B. Whipp,et al.  Spatial heterogeneity of quadriceps muscle deoxygenation kinetics during cycle exercise. , 2007, Journal of applied physiology.

[28]  H. Rossiter,et al.  A validated model of oxygen uptake and circulatory dynamic interactions at exercise onset in humans. , 2013, Journal of applied physiology.

[29]  H. Rossiter,et al.  Exercise: Kinetic considerations for gas exchange. , 2010, Comprehensive Physiology.

[30]  D. Paterson,et al.  Characterizing the profile of muscle deoxygenation during ramp incremental exercise in young men , 2012, European Journal of Applied Physiology.

[31]  S. Ward,et al.  Influence of exercise intensity on the on‐ and off‐transient kinetics of pulmonary oxygen uptake in humans , 2001, The Journal of physiology.

[32]  Pulmonary O2 uptake kinetics during moderate-intensity exercise transitions initiated from low versus elevated metabolic rates: insights from manipulations in cadence , 2014, European Journal of Applied Physiology.