Abstract
The aim of the current study was to investigate whether carbohydrate mouth rinsing works synergistically with caffeine to augment high-intensity running in a fed state. Eight participants completed a total of three trials; (1) placebo (PLA) trial (placebo capsule + placebo mouth rinse), (2) caffeine (CAF) trial (400 mg caffeine + placebo mouth rinse) and (3) carbohydrate mouth rinse + caffeine (CMR + CAF) trial (400 mg caffeine + 6% carbohydrate mouth rinse). Each trial consisted of a 45 min steady-state run at 65% VO2max, followed by 90% VO2max high-intensity intervals (HIIT) at 1 min and subsequently by a 1 min recovery walking at 6 km·h−1, until exhaustion. Both CAF (46.8 ± 20.1 min) and CMR + CAF (46.9 ± 18.4 min) time to exhaustion were significantly greater than the PLA group (36.2 ± 14.8 min, p < 0.001). Post hoc analysis revealed that there was a significant increase in time to exhaustion between PLA and CMR + CAF (p = 0.006) and PLA and CAF (p = 0.017) but not between CAF and CMR + CAF (p = 0.99). In conclusion, we provide novel data that suggest that caffeine alone would likely suffice as an ergogenic aid during high-intensity running while in a fed state.
Highlights
It has been hypothesized that the benefits of exogenous carbohydrate during high-intensity exercise may be mediated through the activation of carbohydrate taste receptors in the mouth, which subsequently activate the central nervous system (CNS) [1]
The authors demonstrated comparable performance improvements with both maltodextrin and glucose, corresponding to 3.1% and 2%, respectively, and demonstrated that both substrates activated reward-related regions of the brain, while artificial sweeteners failed to have the same effect. These findings would lend support to the hypothesis of CNS-mediated effects of carbohydrate mouth rinse (CMR) which may be independent of taste or sweetness, given that maltodextrin is a flavourless polymer of glucose and that artificial sweeteners mimicking a sweet taste failed to provide the same response
Adjustment revealed that there was a significant increase in time to exhaustion between PLA and CMR + CAF (p = 0.006; d = 0.51; moderate), with a mean increase of 10.7 min (29%)
Summary
It has been hypothesized that the benefits of exogenous carbohydrate during high-intensity exercise may be mediated through the activation of carbohydrate taste receptors in the mouth, which subsequently activate the central nervous system (CNS) [1]. Examined the effects of glucose, maltodextrin and artificial sweeteners on exercise performance and by functional magnetic resonance imaging (f MRI). The authors demonstrated comparable performance improvements with both maltodextrin and glucose, corresponding to 3.1% and 2%, respectively, and demonstrated that both substrates activated reward-related regions of the brain, while artificial sweeteners failed to have the same effect. These findings would lend support to the hypothesis of CNS-mediated effects of CMR which may be independent of taste or sweetness, given that maltodextrin is a flavourless polymer of glucose and that artificial sweeteners mimicking a sweet taste failed to provide the same response
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