In this blog, Chief Science Officer Dr. Luke Bucci explains why, even though glucose is the body’s fuel source, Liquid Shot mixes glucose with non-glucose carb sources to exceed the amount of energy glucose can provide on its own. He also summarizes the body’s love/hate relationship with fructose, explaining why pure fructose (which so many other exercise fuel products contain) is actually a hindrance to energy production.


Energy is fuel, fuel is carbohydrates, and the carbohydrate we want is glucose. When glucose supply drops, exercise performance suffers. Eventually, it falls off a cliff, which we all know as a bonking. Regardless of where it comes from, glucose is The King. When Dextrose Elvis has left the building, you’re done. Continuing to exercise with depleted glucose levels leads to serious deleterious effects like bonking and also risks injuries.

So for endurance performance, it’s all about glucose, but getting that glucose to muscles in timelines and quantities that actually support (rather than impede) performance isn’t as straightforward as “consume sugar; go farther.” There is a limit to how much glucose your cells can uptake and convert to energy at a given time.

To get around this limitation with Liquid Shot and maximize energy production, we did what we always do: turn to the scientific literature and our own work with endurance nutrition.


Clinical research and human studies have repeatedly shown that a combination of multiple carbohydrates is better than a single source for the absorption and utilization of blood glucose, because each source uses a different digestive pathway for intestinal transport, so the limit on absorbing pure glucose can be circumvented and fuel levels can push beyond where they’d be with glucose alone. This delivery strategy is known as Multiple Transportable Carbohydrates (MTC) in the scientific literature.

In accordance with the MTC strategy, Liquid Shot optimizes intake, uptake, and utilization by including three different carb sources:

  • maltodextrin (short-medium length glucose polymer, a complex carbohydrate),
  • glucose (dextrose), and
  • sucrose (table sugar, glucose:fructose).

Based on scientific research and supported by empirical evidence, this MTC combination in the right ratios can almost double the previously observed levels of maximum glucose-to-energy oxidation (or simply, burn) rates.

You read that right, but we’ll repeat it because it’s pretty impressive: the MTCs in Liquid Shot’s formula can almost double the rate of energy oxidation compared to consuming glucose alone.

To quickly summarize, your body uses glucose to create ATP, which it then uses as energy; however, your gut can only uptake and process so much glucose at once, and it’s easy to outpace that limit during exercise. Liquid Shot’s inclusion of maltodextrin and sucrose sidesteps that limit, delivering more fuel to your muscles than pure glucose alone, which accounts for that impressive potential doubling of energy oxidation rates.

Advantages of Liquid Shot’s Carbohydrate Blend (MTCs)


Long-term endurance exercise performance Long-term endurance exercise fatigue
Fluid delivery Dehydration
Absorption of CHO into the bloodstream CHO inside the gut during exercise
Glucose oxidation (energy) in muscles Less premature glycogen use (=glycogen sparing)
Faster gastric emptying Gastric & intestinal discomfort / distress
Better mood & mental functions Worse mood & mental functions
Post-exercise recovery (glycogen repletion, musculoskeletal function) Worse Delayed Onset Muscle Soreness (DOMS) and/or EIMD (Exercise-Induced Muscle Damage)



You’ve got the summary, now here’s a deeper explanation of how Liquid Shot lifts the fueling limit.

We want carbs for energy to fuel our physical performance. The sooner the better. There are three major types of carbs that are converted to metabolic energy: monosaccharides, disaccharides, and polysaccharides. Monosaccharides are single sugar molecules like glucose and fructose. Disaccharides are two sugars stuck together in a specific way, like the sucrose in Liquid Shot. Polysaccharides can range from three to millions of single-molecule sugars strung together like pearls on a necklace, like Liquid Shot’s maltodextrin, or branches of a tree.

All carb shapes and sizes can be found in foods, and human metabolism is better equipped to handle certain preferred combinations – this is where MTC theory comes into play, and it’s the reason why Liquid Shot includes glucose, maltodextrin, and sucrose.

We’ve already established why glucose matters – it’s The King. Maltodextrin is included because its polysaccharide structure is basically a glucose carpool. It’s a more efficient way to deliver glucose in bulk, and your body produces an enzyme to easily unpack the glucose once it arrives. (See more details on maltodextrin.)

That leaves sucrose, which requires a little segue about fructose to explain why including sucrose – and just as importantly, omitting pure fructose – is Liquid Shot’s secret for surpassing the glucose limit.


Early research found a limit to how much glucose exercising humans can utilize – 30-60 grams/hour. The source mattered little; whether it was glucose, maltose, glucose polymers or a combination of those, the limit was similar. But this was from glucose-only or single carb-only studies.

pure fructose ultimately produces exactly as much energy as it consumes during energy production, making it net-zero for fueling purposes

Including fructose in MTC formulas provides an avenue for increasing this limit. Adding fructose along with glucose compounds gives an extra boost of energy – but only once glucose levels are saturated or depleted. It normally takes more than 2.5 hours of intense endurance exercise (like cycling) or five hours of running to benefit from extra fructose, and anything less than a maximum effort has not shown clear benefits from fructose ingestion. Thus, fructose can boost endurance exercise performance, but with conditions.

Once ingested, fructose moves through the stomach similarly to glucose, but after that, it has its own set of receptors and transporters that allow it to enter digestive tract cells independent of glucose. This means that if you have saturated (maxed out) the amount of glucose you can absorb, you can still get more carbs into your cells with fructose, which is where the potential increase in fuel comes from.

But! For fructose to become energy, it needs to first be converted to glucose. This process requires a phosphate group, and the phosphate comes from ATP, the very energy compound we’re trying to produce for fuel. So pure fructose ultimately produces exactly as much energy as it consumes during energy production, making it net-zero for fueling purposes. (See more details here.)

Fructose does bypass the metering of glucose, so it’s a way to sneak additional energy into cells, but it consumes as much ATP as it produces, so it’s net zero on the fuel front. The energy output from fructose compared to glucose is one less ATP per molecule – in other words, equivalent amounts of glucose and fructose do not yield the same amount of energy for your muscles. Glucose always wins that calculation.


Despite all that, fructose is still a crucial element in the MTC equation for unlocking a higher fuel ceiling. You just need enough glucose saturation to even out the loss in ATP output. This can be accomplished in two ways:

  1. Add pure fructose to lots of glucose and/or maltodextrin.
  2. Add sucrose (glucose:fructose), instead.

In Liquid Shot, we opt for the second option because we found empirically that sucrose works better than pure fructose for long-term exercise.

your body can convert the fructose in sucrose for additional energy without an overall drag on ATP production

Since sucrose is a disaccharide containing glucose and fructose, it effectively provides the glucose needed to convert its own fructose into ATP before any ATP loss is detected by your muscles. It’s BYOG for the ATP BBQ. So even before your body is able to efficiently use pure fructose (recall that that takes full glucose saturation or about 2.5 hours on the bike/5 hours running), your body can convert the fructose in sucrose for additional energy without an overall drag on ATP production.

Given that fructose can sneak across membranes that wouldn’t otherwise accept more glucose, the result is that your cells can absorb fuel beyond the pure glucose limit without first requiring glucose saturation, allowing those almost double energy oxidation gains.

By working with your body’s infrastructure to deliver additional fuel, Liquid Shot’s MTCs maximize energy levels by using glucose, glucose polymers (maltodextrin), and sucrose (glucose:fructose). It’s a perfect (dare we say “textbook”?) example of how MTCs can provide more fuel that’s more easily absorbed than pure glucose alone – and how First Endurance uses the latest technology and scientific research to push the limits of endurance nutrition.

July 23, 2021 — Luke Bucci
Tags: Liquid Shot

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