Issue #23: Mouth Rinse Magic

🥞 Fueling for Performance

👨‍💻 Introduction

Topic: Carb Rinsing

The carb king is back, but this time, we're not even talking about ingesting carbs. The jury is pretty much out on high carb = high performance, but there is some potentially even more interesting research on how carbs can impact performance without even swallowing them. This research is focused on how even just swishing a carbohydrate (CHO) mix around in your mouth, without swallowing a drop, can enhance performance. The so‑called “carb mouth rinse” trick taps into your brain’s reward and motor centers, giving you a small but measurable boost before you even digest anything. Let's dive in.

🔍️ Deep Dive

What’s going on?

In recent years, sport nutrition researchers have moved beyond just “eating carbs = fuel” to explore how sensing carbs in the mouth can influence performance. The key findings from these reviews:

• When athletes rinse their mouth with a ~6% carbohydrate solution (example: maltodextrin) for ~5‑20 seconds, then spit it out, performance in endurance‑type tasks (30‑60 minutes) improves. For example, a meta‑analysis of cycling time‑trials found that compared with placebo, CHO mouth rinsing improved mean power output.

• The proposed mechanism is not improved fuel delivery (you’re not actually swallowing the carbs, so metabolic contribution is low). Instead it’s central: oral carbohydrate receptors activate brain reward/motor‑control areas, which increases motor drive or reduces perceived effort.

• The magnitude of benefit is modest – many studies report ~1–4% improvements in endurance contexts (if I can squeeze out a 1% gain, I'm taking my chances). 

• The effect is stronger when the exercise is of moderate duration (~30-60 mins), when athletes are in a fasted or low‑glycogen state, or when the fatigue is central, meaning the limitation comes from the brain or nervous system (motivation, neural drive, or perceived effort), rather than purely peripheral (fatigue caused by the muscles themselves running out of energy).

• For very short sprint efforts (<5 mins) or heavy strength efforts where peripheral fatigue dominates, the benefit is inconsistent or trivial.

Why It Matters

In HYROX or mixed running/functional events, there are stretches when you’re redlining – your breathing is heavy, effort stays sky‑high, and every rep feels like a grind. In those moments, actually taking in carbs probably won’t move the needle much because the effort isn’t long enough for digestion or glycogen replenishment to help. Plus, it's just tough to swallow a gel when they’re gasping for air. That’s where the “carb rinse” comes in. A quick swish tells your brain, in essence, “fuel is coming,” giving you a subtle mental and neural boost to push through that brutal back half.

🧪 Lab Notes

Here’s how you can think about incorporating this:

• Solution

  • Prepare ~25 mL of a carb solution to carry with you during your workout, run, or race.

  • Example: 1st Phorm Ultra-formance → it’s already a carb + electrolyte blend perfect for the mouth‑rinse protocol

• The Protocol

  • Rinse/swish for ~5-20 seconds, then spit out, during an intense session when swallowing or intaking carbs is not ideal for various reasons (like gut trouble).

• When to Use

  • Races/training where ingestion is limited and the effort is maybe 30-75 minutes total.

• Expectations

  • You might see a ~1-3% improvement (higher average power, lower perceived effort).

  • Not huge, but meaningful at the margins.

• Limitations

  • Smaller effect if glycogen stores are topped off.

  • Little benefit for short or strength‑dominant efforts.

  • Not a replacement for proper nutrition or pre race fueling (!!!).