Discussion
Ataide-Silva, carbohydrate mouth
CONTRACTION
Prior research has found tasting an unpleasant bitter quinine solution to exhibit ergogenic potential by enhancing cycling sprint performance (Gam et al. In the present study, there was no significant difference in VM or VL motor-evoked potentials, during a 10% of MVC contraction, between the unpleasant bitter or salt solutions and the control conditions. Conversely, Gam et al. (Tasting the bitter compound quinine has previously been shown to improve cycling sprint performance (Gam et al. The present data showed a significantly greater increase in heart rate after mouth rinsing and ingesting the bitter or salty solutions compared to control conditions. However, the data from the no solution and water control conditions show that only 5–6 bpm of the increase in heart rate can be attributed to the unpleasant taste itself. An increase of 14 bpm was caused by moving the arm and tilting back the head, evidenced by the no solution condition increasing heart rate by 14 bpm. A further 4 bpm was attributable to rinsing a solution around the mouth, as evidenced by water increasing heart rate by 18 bpm. Therefore, although the increase in heart rate suggests the unpleasant tastes caused a greater autonomic nervous system disturbance, the small changes observed in heart rate at rest are unlikely to be relevant to exercise performance. Supporting this, mouth rinsing and ingesting quinine has been shown to improve 30 s cycling sprint performance; however, it had no effect on heart rate immediately post-exercise (Gam et al. In the present study, participants were able to eat up to 1 h before testing and so were in the fed state when testing commenced. Athletes typically train and race in the fed state and so this ensured ecological validity. However, it is possible that participants’ responses to the unpleasant tastes were diminished, because they were satiated. Indeed, the ergogenic effect of carbohydrate mouth rinsing appears to be dependent on if an individual is pre- or post-prandial. When directly manipulating nutritional state, most research finds carbohydrate mouth rinsing to improve performance to a greater extent when individuals are fasted compared to fed (Ataide-Silva et al. The placebo effect is an advantageous outcome of an individuals expected or learned response to a specific stimulus (Beedie et al. 