Biochemical Background of the VO2 On-Kinetics in Skeletal Muscles

Abstract

This review discusses the present knowledge on the oxygen uptake kinetics at the onset of exercise in skeletal muscle and the contribution of a previously developed computer model of oxidative phosphorylation in intact skeletal muscle to the understanding of the factors determining this kinetics on the biochemical level. It has been demonstrated recently that an increase in the total creatine pool [PCr + Cr] and in glycolytic ATP supply lengthen the half-transition time of the O 2 on-kinetics, while an increase in mitochondria content, in parallel activation of ATP supply and ATP usage, in muscle oxygen concentration, in proton leak, in resting energy demand, in resting cytosolic pH, and in initial alkalization diminish this parameter. It has also been shown that the half-transition time is near-linearly proportional to the absolute difference between the phosphocreatine concentration during work and at rest (ΔPCr). The present review discusses whether the O 2 on-kinetics on the muscle level is strictly or only approximately exponential. Finally, it is postulated that a short transition time of the O 2 on-kinetics in itself does not need be profitable for the skeletal muscle functioning during exercise, but usually a short transition time is correlated with factors that improve exercise capacity. The transition time is a phenomenological parameter resulting from the biochemical properties of the system and not a physical factor that can cause anything in the system.Key words: creatine kinase, kinetic model, mitochondrial respiration, oxidative phosphorylation, oxygen uptake kinetics, physical exercise, skeletal muscle.An increase in the power output generated by skeletal muscle requires a rapid adjustment of ATP production in order to meet elevated energy demand. The rate of ATP usage can rise many times (even more than 100) during rest-to-work transition. The rate of ATP consumption must be matched by the rate of ATP production to avoid significant changes in [ATP] (ATP concentration is essentially constant during rest-to-work transition). The transformation of phosphocreatine (PCr) to creatine (Cr) catalyzed by creatine kinase is the main process that resynthesizes ATP from ADP during the first seconds of exercise. Next, the ATP production by anaerobic glycolysis is activated. At low and moderate exercise intensities, anaerobic glycolysis is essentially switched off after several (tens of) seconds, and the ATP synthesis is then gradually taken over by oxidative phosphorylation in mitochondria, while at high exercise intensities the anaerobic glycolysis remains a significant ATP supplier until the termination of exercise (for review, see [1][2][3]). Krogh and Lindhard [4] first showed that during the transition from rest to work in humans, the pulmonary oxygen uptake does not rise instantly, but there is a certain transient state during which the oxygen uptake rate ( O 2 ) rises at the onset of exercise. Since then, numerous studies on O 2 on-kinetics have been performed. Nevertheless, the biochemica...

Influence of dietary creatine supplementation on muscle phosphocreatine kinetics during knee-extensor exercise in humans

“…Although a number of studies using isolated mitochondria or animal models have provided evidence in favor of the notion that muscle [PCr] (and/or V O 2 ) kinetics are related to the total muscle Cr content (16,35,46), to our knowledge the present data are the first to demonstrate that an increase in muscle [PCr], and thus an increase in metabolic capacitance (45), is associated with a slowing of muscle [PCr] kinetics during constant-load submaximal exercise and subse- quent recovery in human subjects. The data also are consistent with the computer modeling predictions of Korzeniewski and Zoladz (37).…”

Phosphocreatine Kinetics in the Calf Muscle of Patients with Bilateral Symptomatic Peripheral Arterial Disease during Exhaustive Incremental Exercise

“…and several other cellular parameters [5,12,13,22,23]. In contrast, the PCr rephosphorylation bases mainly on the oxygen-dependent ATP production [21].…”

The effects of creatine supplementation on thermoregulation and physical (cognitive) performance: a review and future prospects

“…The coupling between PCr and O 2 kinetics at the onset of exercise until steady state has been well characterised (Binzoni et al 1992;Barstow et al 1994;McCreary et al 1996;Rossiter et al 1999;Rossiter et al 2001;Rossiter et al 2002;Korzeniewski and Zoladz 2006). The ratio of ATP/ADP and PCr/Cr are linked in the mitochondria to the creatine kinase (CK) reaction (Chance and Williams 1955;Meyer et al 1984;Mahler 1985;Balaban 1990).…”