Mouth rinsing and ingesting salty or bitter solutions does not influence corticomotor excitability or neuromuscular function

Purpose To explore the efect of tasting unpleasant salty or bitter solutions on lower limb corticomotor excitability and neuromuscular function. Methods Nine females and eleven males participated (age: 27±7 years, BMI: 25.3±4.0 kg m−2). Unpleasant salty (1 M) and bitter (2 mM quinine) solutions were compared to water, sweetened water, and no solution, which functioned as control conditions. In a non-blinded randomized cross-over order, each solution was mouth rinsed (10 s) and ingested before perceptual responses, instantaneous heart rate (a marker of autonomic nervous system activation), quadricep corticomotor excitability (motor-evoked potential amplitude) and neuromuscular function during a maximal voluntary contraction (maximum voluntary force, resting twitch force, voluntary activation, 0–50 ms impulse, 0–100 impulse, 100–200 ms impulse) were measured. Results Hedonic value (water: 47±8%, sweet: 23±17%, salt: 71±8%, bitter: 80±10%), taste intensity, unpleasantness and increases in heart rate (no solution: 14±5 bpm, water: 18±5 bpm, sweet: 20±5 bpm, salt: 24±7 bpm, bitter: 23±6 bpm) were signifcantly higher in the salty and bitter conditions compared to control conditions. Nausea was low in all conditions (<15%) but was signifcantly higher in salty and bitter conditions compared to water (water: 3±5%, sweet: 6±13%, salt: 7±9%, bitter: 14±16%). There was no signifcant diference between conditions in neuromuscular function or corticomotor excitability variables. Conclusion At rest, unpleasant tastes appear to have no infuence on quadricep corticomotor excitability or neuromuscular function. These data question the mechanisms via which unpleasant tastes are proposed to infuence exercise performance.