Effect of creatine supplementation on oxygen uptake kinetics during submaximal cycle exercise

Abstract

The purpose of this study was to test the effect of oral creatine (Cr) supplementation on pulmonary oxygen uptake (VO(2)) kinetics during moderate [below ventilatory threshold (VT)] and heavy (above VT) submaximal cycle exercise. Nine subjects (7 men; means +/- SD: age 28 +/- 3 yr, body mass 73.2 +/- 5.6 kg, maximal VO(2) 46.4 +/- 8.0 ml. kg(-1). min(-1)) volunteered to participate in this study. Subjects performed transitions of 6-min duration from unloaded cycling to moderate (80% VT; 8-12 repeats) and heavy exercise (50% change; i.e., halfway between VT and maximal VO(2); 4-6 repeats), both in the control condition and after Cr loading, in a crossover design. The Cr loading regimen involved oral consumption of 20 g/day of Cr monohydrate for 5 days, followed by a maintenance dose of 5 g/day thereafter. VO(2) was measured breath by breath and modeled by using two (moderate) or three (heavy) exponential terms. For moderate exercise, there were no differences in the parameters of the VO(2) kinetic response between control and Cr-loaded conditions. For heavy exercise, the time-based parameters of the VO(2) response were unchanged, but the amplitude of the primary component was significantly reduced with Cr loading (means +/- SE: control 2.00 +/- 0.12 l/min; Cr loaded 1.92 +/- 0.10 l/min; P < 0.05) as was the end-exercise VO(2) (control 2.19 +/- 0.13 l/min; Cr loaded 2.12 +/- 0.14 l/min; P < 0.05). The magnitude of the reduction in submaximal VO(2) with Cr loading was significantly correlated with the percentage of type II fibers in the vastus lateralis (r = 0.87; P < 0.01; n = 7), indicating that the effect might be related to changes in motor unit recruitment patterns or the volume of muscle activated.

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

“…Interestingly, however, the value was increased by ϳ10 and ϳ4% for moderate-intensity and heavy-intensity exercise, respectively. It is possible that intersubject variability in the changes to muscle Cr content in response to dietary Cr supplementation (8,12), which was not directly assessed by Jones et al (28), precluded the attainment of statistical significance. In the same study, steady-state V O 2 was not different following Cr loading for moderate-intensity exercise, consistent with the similar change in [PCr] observed in the present study.…”

“…According to Meyer's electrical analog model, a greater muscle total Cr content consequent to dietary Cr "loading" would be expected to result in slower muscle [PCr] and V O 2 kinetics. In the only study to date on this topic, Jones et al (28) were unable to detect a significant change in the phase II pulmonary V O 2 kinetics following Cr loading at either moderate (i.e., below the estimated lactate threshold, LT) or heavy (i.e., ϾLT) intensities of cycle ergometer exercise. However, pulmonary V O 2 kinetics can only provide an indirect estimate of muscle [PCr] or V O 2 kinetics (4,18,56), and it is possible that such measurements were not sufficiently sensitive to detect changes in the dynamics of muscle oxidative metabolism following Cr loading.…”

Thigh muscle activation distribution and pulmonary V̇o2kinetics during moderate, heavy, and very heavy intensity cycling exercise in humans

“…It has been repeatedly demonstrated that the muscle and pulmonary V O 2 responses during heavy and very heavy intensity exercise manifest an additional excess component supplementing the underlying fundamental exponential response kinetics (e.g., Refs. 7,8,14,16,17,19,27,28,37,40). While many mechanisms for this V O 2 slow component have been suggested (30), the most commonly proposed view is that of ongoing muscle recruitment during the slow component phase, presumably mediated through ongoing muscle fatigue.…”

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

“…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). An increase in the total creatine pool [PCr + Cr] through Cr loading has been shown to influence the O 2 on-kinetics (Jones et al 2002;Jones et al 2009). In particular, Jones et al (2002) There has been a limited focus of the Cr literature on endurance exercise performance given the purported primary mechanism of action of Cr is to enhance the capacity for PCr resynthesis during recovery from repeated bouts of intense exercise.…”

“…An increase in the total creatine pool [PCr + Cr] through Cr loading has been shown to influence the O 2 on-kinetics (Jones et al 2002;Jones et al 2009). In particular, Jones et al (2002) There has been a limited focus of the Cr literature on endurance exercise performance given the purported primary mechanism of action of Cr is to enhance the capacity for PCr resynthesis during recovery from repeated bouts of intense exercise. In one of the first studies to investigate the effects of 21g Cr monohydrate + 21g dextrose for 5 days during intense endurance exercise lasting approximately 1 hour, no effect on performance 8 was reported although the accumulation of inosine monophosphate (IMP, a marker of muscle energy balance) at the end of the performance ride was significantly lower on the Cr trial.…”