Why are carbohydrates so important for endurance performance in IB SEHS?

Carbohydrates are important in IB SEHS because they provide glucose for ATP production and can be stored as glycogen for later use. During prolonged exercise, muscles need ATP continuously, and carbohydrate metabolism can support a higher rate of ATP resynthesis than fat. That matters when an athlete is trying to hold a strong pace rather than simply keep moving. Carbohydrates are also strongly linked to maintaining exercise intensity, which is a frequent angle in exam questions. When students explain carbohydrates, they should include the terms glucose, glycogen, and ATP, and then connect them to intensity and fatigue. The highest scoring responses usually add a brief applied example, such as distance running, cycling, or rowing.

What happens when glycogen stores get low during endurance exercise?

When glycogen stores fall, performance commonly declines because the athlete cannot maintain the same intensity. In IB SEHS, you can describe this as a shift toward greater fat oxidation, which provides plenty of energy but at a slower rate of ATP resynthesis. This makes it harder to sustain moderate to high intensity efforts, even if the athlete is still working aerobically. Many athletes experience this as "hitting the wall," where pace drops and perceived exertion rises. A clear exam answer also notes that liver glycogen helps maintain blood glucose, so low stores can affect central and peripheral fatigue. If you connect glycogen depletion to both a physiological mechanism and an observable performance outcome, you are usually writing at the right level.

How do IB SEHS exam questions test carbohydrates and endurance?

IB SEHS questions rarely reward a list of facts without linkage. Examiners often want applied chains like: carbohydrate availability influences substrate use, substrate use influences ATP resynthesis rate, and that influences sustainable exercise intensity. You may be given a scenario (for example, a marathon runner slowing late in the event) and asked to explain why, using correct terminology. Strong answers use glycogen, glucose, ATP, intensity, and fatigue in one coherent explanation rather than as isolated definitions. Another common approach is comparing fuels, where you explain why fat cannot support the same intensity despite being a large energy store. The best preparation is practising exam-style prompts and then tightening your phrasing to match command terms, which is exactly what RevisionDojo’s Questionbank and AI feedback are built for.

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IB SEHS: Carbohydrates and Endurance Performance

IB SEHS

RevisionDojo Team

•1/7/2026•6 min read

The first time most athletes learn what glycogen is, it is not in a textbook. It is halfway through a long run, when the legs turn heavy and the mind starts negotiating with time. In IB SEHS, that moment matters because it is a clean, real-world example of how carbohydrates shape endurance performance: when carbohydrate availability drops, pace usually drops with it.

This article breaks down the role of carbohydrates in endurance performance for IB SEHS students, with the exact terms examiners expect: glucose, glycogen, ATP, exercise intensity, and fatigue.

Quick IB SEHS checklist (what to say in exams)

Carbohydrates are broken down into glucose to help produce ATP.
Carbohydrates are stored as glycogen in muscle and liver.
At moderate to high intensity, glycogen is the preferred fuel.
Glycogen depletion is strongly linked to fatigue and reduced pace ("hitting the wall").
Fat can supply lots of energy, but at a slower rate than carbohydrate.

For syllabus-aligned support, keep these RevisionDojo pages open while you revise: Nutrition for sport, exercise and health and Topic A.2 Hydration and Nutrition.

IB SEHS explanation: why carbohydrates power endurance

In IB SEHS, carbohydrates matter because they supply a fast, usable pathway to ATP resynthesis. During endurance exercise, working muscles need a continuous ATP supply to keep cross-bridges cycling and contractions consistent. Carbohydrates provide glucose for aerobic metabolism, and glycogen offers a convenient stored form that can be rapidly mobilized.

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IB SEHS: Carbohydrates and Endurance Performance | RevisionDojo

IB SEHS: Carbohydrates and Endurance Performance

IB SEHS

RevisionDojo Team

•1/7/2026•6 min read

This article breaks down the role of carbohydrates in endurance performance for IB SEHS students, with the exact terms examiners expect: glucose, glycogen, ATP, exercise intensity, and fatigue.

Quick IB SEHS checklist (what to say in exams)

Carbohydrates are broken down into glucose to help produce ATP.
Carbohydrates are stored as glycogen in muscle and liver.
At moderate to high intensity, glycogen is the preferred fuel.
Glycogen depletion is strongly linked to fatigue and reduced pace ("hitting the wall").
Fat can supply lots of energy, but at a slower rate than carbohydrate.