Welcome to my weekly summary of the latest research from the world of sports science!
These three studies dive into the nuances of fueling. From showing that carbs can still improve performance without being swallowed, to reframing bonking as a blood-sugar problem rather than empty muscles and finding that lower caffeine doses may work best on the bike, these are some practical insights for athletes looking to perform better with less gut distress and fewer side effects—read on!
Dissolvable Carb Strips Improve Endurance Without Gut Issues
This study tested whether carbohydrates need to be swallowed to improve endurance performance. Eighteen endurance-trained athletes completed three randomized 12.87 km treadmill time trials, using either dissolvable carbohydrate mouth strips, a carbohydrate mouth rinse, or a plain water rinse. Each intervention was done at the start of the run and every mile thereafter.
The dissolvable strips significantly improved finishing time and pace compared to plain water, while the mouth rinse showed smaller, less consistent improvements. Heart rate was higher with the strips, suggesting greater physiological activation, but perceived effort did not change—athletes ran faster without feeling like they were working harder.
My thoughts: What’s really interesting here is the mechanism. By “tricking” the body into thinking it’s about to receive carbohydrates, performance improves even without ingestion. Mouth rinses have shown small effects before, but these dissolvable strips appear way more effective, likely because they provide longer exposure to oral carbohydrate sensors. For endurance athletes who struggle with GI distress during long efforts, this could be a practical way to get the performance boost without upsetting the gut. The brain clearly plays a bigger role in endurance than we often admit.
Maybe Bonking Isn’t About Empty Muscles
This review challenges the idea that endurance fatigue is caused by muscles running out of glycogen. Looking across more than 160 studies, the authors argue that falling blood glucose, not empty muscle glycogen, is the main trigger for fatigue during long exercise. In 88% of studies where carbohydrate intake improved performance, blood glucose was dropping in the placebo group, pointing to exercise-induced hypoglycemia as the key limiter. Muscle energy levels remained stable, suggesting the brain reduces power output to protect itself when blood sugar falls too low. This helps explain why even small amounts of carbohydrate during exercise can improve performance—by stabilizing blood glucose rather than refilling muscle glycogen.
My thoughts: I love papers that challenge old paradigms. Every endurance athlete knows the “bonk” story, but low glycogen alone never fully explained it. It’s likely the effect of low glycogen (especially on blood glucose and the brain) that makes you want to lie down mid-race. If this is right, smarter fueling strategies could help delay end-of-race fatigue.
Why Less Caffeine May Be Better on the Bike
This review examined the effects of caffeine on cycling performance. Across a wide range of study designs, performance tests, and athlete populations, caffeine consistently improved cycling performance. Improvements in power output and time-trial results were seen across both trained and recreational cyclists, and what stood out was that lower caffeine doses often produced similar or better performance benefits than higher doses while minimizing side effects. The performance benefits also appeared stronger in older athletes, suggesting caffeine sensitivity may increase with age. Overall, the findings support moderate, well-timed caffeine intake rather than aggressive dosing strategies.
My thoughts: There’s nothing new about caffeine helping cycling performance, but the dose finding is interesting. Lower doses seem to work better, and the effect may be stronger as you get older. So on race day, I’d go for a single shot of espresso—not your usual triple.
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