Can a carb mouth rinse enhance performance?

A recent study published this month looked at whether using a carbohydrate mouth rinse (CMR) improved resistance exercise performance. Researchers looked at concentric peak power, eccentric peak power, average power, total work and rate of perceived exertion in participants.

How was it tested?

Researchers had 20 young men in Taiwan without any known health conditions perform the same resistance exercise session on two separate occasions, one week apart. After warming up, the participants rinsed their mouth with either 25 mL of a CMR (6.4% maltodextrin) or placebo (plain water) for 20 seconds, spitting it out after. Immediately after rinsing, participants used a flywheel trainer (Exxentric kBox) to perform 5 sets of 6 reps of Romanian deadlifts, with 3 minutes of rest between. The men all were required to not have eaten for at least three hours before the workout, and had instructions from a registered dietitian as to what they should eat for breakfast and lunch on the workout day, and that diet was the same before both workouts.

What did researchers find?

Compared to the water placebo, researchers found increases in Peak Concentric Power (584 vs 523 watts); Peak Eccentric Power (682 vs 596 watts); Average Power (296 x 262 watts); and Total Work (17.3 vs 15.5 kilojoules). Although perceived rate of exertion did not differ, participants were shown to perform MORE work.

What does it mean?

Impact of Carbohydrate Mouth Rinsing on Exercise Performance

We now that ingesting carbs prior to exercise can improve performance, but in this case it’s not necessarily because of glycogen availability or hypoglycemia, but by altering the central nervous system and affecting motor unit recruitment and power output. CMR can provide a similar performance enhancement. This is attributed to the activation of brain regions related to motor activity, motivation, and reward upon detecting carbohydrates in the mouth.

Consistency of CMR Effectiveness

While CMR has shown potential to enhance exercise performance, the research does not consistently support its ability to always increase energy production. The study emphasizes that the effectiveness of CMR can be influenced by various factors, and its benefits are generally more consistent for endurance exercise than for resistance exercise. Notably, CMR does not seem to enhance 1-repetition maximum tests but shows potential in improving muscular endurance, especially during resistance exercises involving multiple repetitions with a sub-maximal load.

Potential Mechanisms of CMR

The paper also delves into the potential mechanisms through which CMR improves resistance exercise performance. It is suggested that CMR counters neuromuscular fatigue, thus sustaining the optimal firing of the central nervous system and allowing for the performance of more repetitions during resistance exercises.

Effectiveness of CMR in Relation to Fasting and Glycogen Depletion

Additionally, the study explores the impact of fasting and glycogen depletion on the effectiveness of CMR. It indicates that CMRs may be more beneficial when exercise is performed after extended fasting or in a glycogen-depleted state. However, conflicting findings exist, with some studies reporting no significant effects of CMR when exercise was not performed after extended fasting or in a glycogen-depleted state.

Influence of Exercise Type and Volume

In relation to the type and volume of exercises, the paper suggests that CMR might have differing effects on upper-body and lower-body exercises. It is noted that the magnitude of benefit from a CMR may be greater when a higher number of exercises is performed, and it seems to provide more significant benefits for lower-body resistance exercises. In conclusion, the paper emphasizes that CMR, particularly with a 6% carbohydrate solution, can potentially increase the total number of repetitions performed during resistance exercise, especially with submaximal loads. However, further research is needed to support its potential differential effects on upper-body versus lower-body exercises and fasted versus fed exercise.

To read the whole study, visit: https://pubmed.ncbi.nlm.nih.gov/38674938/