Impact of a Carbohydrate Mouth Rinse on Motor Performance and Corticospinal Motor Excitability

Abstract

Application of a carbohydrate (CHO) mouth rinse (MR) prior to exercise has been shown to improve physical performance and facilitate corticospinal motor excitability. It is unclear if different forms of CHO impact this phenomenon. PURPOSE: The purpose of this investigation is to determine the effects of different forms of a CHO MR on muscular performance and corticospinal motor excitability. METHODS: Ten normal healthy subjects (5 females, 5 males; 25±1 years; 1.71±0.03 m 73±5 kg) completed 4 trials each separated by at least 48 hours. A different MR condition was applied during each trial (Placebo (PLAC), 6.4% glucose (GLU), 6.4% maltose (MAL), 6.4% maltodextrin (MDX)). Maximal voluntary contraction (MVC) of the right knee extensors and motor-evoked potential (MEP) of the right vastus medialis was determined pre (10 min before), immediately after, and post (10 min after) application of the MR. MEP was precipitated by applying transcranial magnetic stimulation (TMS) during muscle contraction (50% of MVC). The MR was held in the mouth for 20 sec and MR treatments were applied using a Latin square design. RESULTS: No differences were found in the change of MEP from pre to immediately after the MW across the conditions (PLAC=1.5±4.4%; GLU=-6.2±11.2%; MAL=3.9±3.4%; MDX=8.9±7.9%). In contrast, the increase in MEP was greater at the post time point in CHO conditions (GLU=-11.3±14.7%, p=0.01; MAL=12.9±7.9%, p=0.07; MDX=28.0±14.4%, p=0.02) as compared to PLAC (PLAC=-14.3±7.8%). MVC was similar at pre (PLAC=260±26 Nm; GLU=241±19 Nm MAL=245±21 Nm; MDX=248±25 Nm), after (PLAC=269±26 Nm; GLU=249±18 Nm MAL=257±19 Nm; MDX=250±23 Nm), and 10 min after (PLAC=262±28 Nm; GLU=256±17 Nm MAL=269±25 Nm; MDX=253±21 Nm) the MW. CONCLUSIONS: CHO MR increased corticospinal motor excitability 10 min after application; however, the form of CHO used did not influence this response. The increase in corticospinal motor excitability did not translate into an improvement in motor performance.