An acute oral dose of caffeine does not alter glucose kinetics during prolonged dynamic exercise in trained endurance athletes

Abstract

This study investigated the possible influence of oral caffeine administration on endogenous glucose production and energy substrate metabolism during prolonged endurance exercise. Twelve trained endurance athletes [seven male, five female; peak oxygen consumption (VO2peak) = 65.5 ml.kg-1.min-1] performed 60 min of cycle ergometry at 65% VO2peak twice, once after oral caffeine administration (6 mg.kg-1) (CAF) and once following consumption of a placebo (PLA). CAF and PLA were administered in a randomized double-blind manner 75 min prior to exercise. Plasma glucose kinetics were determined with a primed-continuous infusion of [6,6-2H]glucose. No differences in oxygen consumption (VO2), and carbon dioxide production (VCO2) were observed between CAF and PLA, at rest or during exercise. Blood glucose concentrations were similar between the two conditions at rest and also during exercise. Exercise did lead to an increase in serum free fatty acid (FFA) concentrations for both conditions; however, no differences were observed between CAF and PLA. Both the plasma glucose rate of appearance (Ra) and disappearance (Rd) increased at the onset of exercise (P < 0.05), but were not affected by CAF, as compared to PLA. CAF did lead to a higher plasma lactate concentration during exercise (P < 0.05). It was concluded that an acute oral dose of caffeine does not influence plasma glucose kinetics or energy substrate oxidation during prolonged exercise in trained endurance athletes. However, CAF did lead to elevated plasma lactate concentrations. The exact mechanism of the increase in plasma lactate concentrations remains to be determined.

Caffeine Use in Sports: Considerations for the Athlete

“…The mechanism for improved endurance, sprint, and power performance had been previously related to a single biologic Journal of Strength and Conditioning Research the TM mechanism, such as glycogen sparing, increased intracellular Ca ++ concentration, or altered excitation-contraction coupling (11,16,18,23,29,55,59). In fact, a caffeine paradigm for improved athletic performance should be multifactorial, extend beyond any single biologic mechanism, and include cognitive perception and habituation ( Figure 2).…”

“…Until recent years, the mechanism for improved endurance performance was considered to be improved lypolysis from adipose and intramuscular triglyceride and conservation of carbohydrate stores (i.e., glycogensparing effects of caffeine) for later use during endurance exercise (16,18,23,55,59). Davis et al (14) proposed a mechanism by which caffeine delays fatigue through its effects on the CNS.…”

The effect of acute dark chocolate consumption on carbohydrate metabolism and performance during rest and exercise

“…However, the effects of methylxanthines (mainly caffeine) on glucose disposal (glucose uptake, rate of disappearance (R d ) or glucose oxidation) have been inconsistent. Most studies showed a decrease (Graham, Battram et al 2008), while others showed no change (Roy et al 2001;Hulston et al 2008) or increase in glucose oxidation during exercise (Yeo et al 2005).…”

Acute effects of caffeine intake on athletic performance: A systematic review and meta-analysis

“…Caffeine may affect performance through both peripheral and central mechanisms. The mechanism for improved endurance, sprint, and power performance has been related to a simple biologic mechanism, such as glycogen sparing, increased intracellular Ca ++ concentration, or altered excitation-contraction coupling [6][7][8][9] . However, a caffeine paradigm for improved athletic performance is a complex, including biologic mechanisms, and cognitive perception 5 .…”