Grace Six Scripts — Fuelling Your Marathon: The Science Says

Grace's six scripts, revised against production notes · Science in Sport · August 2026

This is the full rewrite of all six scripts, incorporating every comment from the review. The headline decisions applied throughout are:

• **Titles:** Anna's curated set in the format "Fuelling Your Marathon: [topic] | The Science Says"
• **Specificity:** Named products (GO RTD, HYDRO tabs, BETA Fuel 80) and a fourth fuelling variable — TYPE — alongside quality, volume and timing
• **Run explainers:** Each run type carries a one-line "what this run is"
• **Voice:** Accessible over formal — Grace over a coffee

Episode 1: Fuelling Your Marathon: Fuelling Training

Approx runtime: 4:45

Key learning

Hitting the wall isn't necessarily a fitness problem. It happens to well-trained marathon runners in every single marathon. And most of the time it's a mismatch between the fuel the race demands and the carbohydrate you've actually got available.

Core concept

We store carbohydrate mainly as glycogen, in our muscles and liver. Think of it as your readily-available fuel reserve. Every run uses some of it, and harder or longer efforts use it faster. Across a marathon block, all those long runs and high mileage add up to a serious, repeated demand on those stores.

The four variables

Before you leave the house, decide four things:

• **Type:** What kind of session is it, and how long?
• **Quality:** What you take, and in what form
• **Volume:** Grams of carbohydrate per hour
• **Timing:** When you fuel

Critical practice

Gut training isn't fixed. Your ability to absorb carbohydrate on the move adapts. Feed your gut at running intensity, regularly, and it gets better at handling volume. Use your longer runs as rehearsals — start early in the block, not in the last few weeks.

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Episode 2: Fuelling Your Marathon: Which Fuels and When

Approx runtime: 5:00

The dividing line

Most of your sessions fall on one side of a line, or the other: 90 minutes.

• **Under 90 minutes:** Single-source fuelling (maltodextrin) — GO Energy gels or drinks
• **Over 90 minutes:** Dual-source fuelling (maltodextrin + fructose) — BETA Fuel

Why the difference matters

Single-source carbohydrate is absorbed and used quickly for energy. Simple, predictable, nothing complicated. But once your sessions push past 90 minutes, carbohydrate demand climbs. Single-source hits a limit because maltodextrin is absorbed through one route, and that route has a ceiling. Dual-source products use two different absorption pathways, which lets you take on and actually use more carbohydrate, with less stomach trouble.

Four mistakes that quietly cost runners time

1. Not planning your fuelling when you plan the session
2. Racing on a plan you've never rehearsed at race pace
3. Assuming more is always better
4. Copying someone else's plan

Key principle

Your gut behaves differently under load — untested is unknown. Get familiar with your intervals until they stop needing a decision.

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Episode 3: Fuelling Your Marathon: How Do Different Training Runs Work?

Approx runtime: 5:10

The framework

Think of your training week as a toolkit. Each run is a different tool, with a different job. Together, across each of your training weeks, they build the range of adaptations you need to perform on race day.

Different sessions lean on your energy systems differently. As intensity goes up, you rely more on carbohydrate and less on fat — and the total carbohydrate a session burns can vary a lot. Which means your fuelling should be matched to the demands of the session.

Run types and their fuelling

Easy run: Start well-fuelled and hydrated. Nothing to add.

Progression run: 40–60g carbohydrate per hour. Start well-fuelled, fuel consistently from the start.

Interval session: 60g carbohydrate per hour. The recoveries give you plenty of chances to take it on.

Tempo and threshold: Under 90 minutes, GO. Over 90, dual-source (BETA Fuel).

Long run: 60–90g carbohydrate per hour — BETA Fuel territory. This is where you practise your fuelling and train your gut.

Race practice: Full dress rehearsal at goal pace with your entire race-day routine. Same products, same volume, same timing. No substitutions.

The key insight

Each run brings different demands and delivers different benefits — so each one calls for its own fuelling plan. Fuel each session for what it actually is, and your training gets more consistent, and more rewarding.

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Episode 4: Fuelling Your Marathon: Tapering & Carbohydrate Loading

Approx runtime: 4:40

The physiology

Your training gives you two things at once. Fitness, and fatigue. Easing off your training, and paying real attention to your nutrition, lets you clear the fatigue — repairing muscle, refilling energy stores, and freshening you up mentally. Over a short window like this, you don't lose the aerobic fitness you've built. What you lose is the tiredness sitting on top of it.

Done properly, tapering and carb loading aren't undoing your training. They're unlocking it.

The taper structure

The usual window is two to three weeks, starting after your full race-rehearsal run.

• **Volume:** Bring it down gradually — roughly a fifth off in the first taper week, closer to two-fifths in the second, and around half in race week
• **Frequency:** Keep the same number of runs, just shorter
• **Intensity:** Hold a little race-pace work in each week to stay sharp
• **Easy days:** Make them easy

Carb loading

Through the taper itself, don't change much — regular, balanced meals and good hydration.

Then, 48 hours out, carbohydrate becomes the priority. You store carbohydrate as glycogen. Race pace burns through it quickly, so you want to start with those stores as full as possible.

Gently up the proportion of carbohydrate in all your meals across those two days. Keep it familiar — your gut has nothing to gain from novelty this week. Light, plain, carb-rich foods, and keep the fibre low.

Be accurate. Work out a target from your bodyweight rather than guessing, then spread it evenly across the day — meals and snacks, and drinks and sports products count too.

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Episode 5: Fuelling Your Marathon: Race Day

Approx runtime: 5:00

The science

Running 42.2 kilometres at marathon pace puts a big demand on your carbohydrate stores. Over a race you can use several hundred grams, depending on your pace, your size and your time on the course. As the race goes on, your glycogen stores start depleting, and holding your target pace gets harder. That's the experience most runners know as hitting the wall. It's still common in every marathon — and it's also largely avoidable.

Your race-day plan by the clock

48 hours before: Continue carb loading steadily

Three hours out: Have your main pre-race meal — usually breakfast. Aim for roughly 3 grams of carbohydrate per kilogram of bodyweight, from light, familiar, easy-to-digest foods. Hydrate steadily, adding electrolytes to suit the conditions.

One hour out: A small top-up of 20–30 grams of carbohydrate, from food or a gel or drink. Keep fluids going gently, easing off as you get closer to the start.

During the race: A practical target for many marathon runners is around 80 grams of carbohydrate an hour — with up to 120 an hour for experienced, competitive runners who've specifically trained their gut to handle it.

The right number for you is the highest one you've actually rehearsed and tolerated in training. Not the one on the packet, and not the one your training partner uses.

Intakes at that level are exactly what dual-source products were built for. Maltodextrin and fructose together let you absorb and use more carbohydrate, with less stomach trouble at those rates. That's why BETA Fuel — including BETA Fuel 80 — is a tried-and-tested marathon choice.

Staying on plan

Set your fuelling intervals and stick to them. Consistent, predictable intake means smooth carbohydrate availability. Stay ahead of any slump. By the time you feel the tank getting low, you're already behind.

You'll have worked out in training what products and flavours suit you. Stick to the plan. Race day is not the day to try something new.

Hydration and electrolytes

Hydration works the same way. Match it to the conditions, not to a fixed volume. Use the aid stations, and take small, steady amounts rather than a lot in one go. Over-drinking is as unhelpful as dehydration.

Electrolytes matter too, especially sodium. How much you need depends on how much you sweat and the conditions on the day. Something like HYDRO tablets makes that easy to manage.

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Episode 6: Fuelling Your Marathon: Recover(ing) Effectively

Approx runtime: 5:15

The principle

The run doesn't make you faster. It creates the stimulus. What you do in the hours afterwards is what turns it into fitness. And it's the part most runners treat as optional.

After is as much a part of the plan as before and during. If the first thing you do after a session is check your phone — set a reminder. Whatever it takes. Have your post-run nutrition ready and waiting. This is not the moment to go shopping.

Recovery nutrition — the three priorities

Carbohydrate: Aim to get some carbohydrate in within the first half hour, when your muscles are most ready to take it back up. 1 gram per kilogram of bodyweight is a useful starting point. If you can't face solids, a carb-rich drink does the job.

Protein: It gives your body the raw material to repair the small-scale muscle damage running causes. A good target after your session is 20–25 grams, in that same 30-minute window. A yoghurt or a shake does the job.

Hydration: Replacing what you've lost is essential — heat and humidity change how much that is. Drink steadily — little and often beats large volumes in one go.

Quick win products

GO Recovery gives you protein and carbohydrate in a single drink. BETA Recovery is there for your bigger sessions and race day. Keep one in the kitbag for the day you get caught out.

Beyond the first 30 minutes

That's your immediate post-session nutrition sorted. But recovery isn't a single moment — it carries on through the rest of the day, in your meals, your snacks, your fluids and your rest. Keep coming back to the same three priorities: carbohydrate, protein, fluid.

Consistent sleep supports every part of recovery. Plan lighter days and rest days after your hardest sessions — and on those days, don't drop the standard of your nutrition. Recovery is a steady, ongoing build, not a switch.

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The Series Framework

Episode 1 — The Training Block: How energy works, the four variables, and why gut training matters

Episode 2 — Fuel Selection: The 90-minute dividing line, single vs. dual-source, and the mistakes that cost time

Episode 3 — Session Types: Every run type has its own job and its own fuelling plan

Episode 4 — Taper & Loading: Clearing fatigue and filling your stores

Episode 5 — Race Day: The clock, the numbers, and the plan that carries you through

Episode 6 — Recovery: Turning stimulus into fitness through post-run nutrition

These six episodes on fuelling your training, choosing what to use, matching it to your sessions, tapering and loading, race day, and recovery form a complete system. Now go and enjoy your next run.