How do you avoid hitting the wall in a marathon?

Q: How do you avoid hitting the wall in a marathon?

Avoid hitting the wall by starting the marathon with full glycogen stores, taking in 30 to 60 g of carbohydrate an hour from the first 30 to 45 minutes, and pacing evenly. Up to 90 g an hour helps on slower, longer races. Practise your fuelling in training so your gut copes with it on race day.

What is "the wall"?

The wall is the sudden collapse in pace many runners feel somewhere between about 30 and 35 km. It is mostly a fuel problem: muscle and liver glycogen run low, blood glucose drops and the brain and legs both feel heavy. Poor pacing, heat, muscle damage and sleep loss add to it. Glycogen is limited, which is why fuel taken during the race matters in events beyond roughly 90 minutes.

How much carbohydrate should you take in?

The standard framework from Jeukendrup (2014) is:

Race duration	Carbohydrate
Under 30 minutes	none needed
30 to 75 minutes	small amounts or a mouth rinse
1 to 2 hours	up to 30 g/h
2 to 3 hours	up to 60 g/h
Over 2.5 hours	up to 90 g/h, using glucose and fructose (about 2:1)

For a 4-hour marathoner, 60 g/h is about 240 g in total. Start early and dose every 15 to 20 minutes rather than in big lumps.

What does that cost?

Using October 2026 prices and our cost per gram of carbohydrate:

Fuel	Cost per g carbohydrate	Cost of 240 g
32Gi Race drink (R470, 68 g per serving)	about R0.58	about R139
Biogen Elite Carb Gel (R44.99, 45 g)	about R1.00	about R240
SiS GO Isotonic Gel (R44.90, 22 g)	about R2.04	about R490
Maurten Gel 100 (R75, 25 g)	about R3.00	about R720

Biogen Liquid Energy Gel (23 g, R26.99) works out near R1.17 per gram. Carbohydrate per gel is not published for 32Gi, GU or Nutritech gels. Full comparisons are in our best energy gels answer.

How do you stop the wall in practice?

Load before the race. See how to carb load.
Fuel from minute 30, not when you feel flat. By then it is late.
Pace evenly. Starting 20 to 30 seconds per km too fast burns glycogen quickly. Run the first half slightly slower than you feel you could.
Train the gut. Practise race intake on long runs, building up gradually; some elite athletes now handle more than 90 g/h with training.
Use caffeine late if it suits you; see caffeine gels.
Hydrate to thirst and do not skip sodium on hot days.
Train the engine. Long runs and tempo work improve fat use and delay the wall.

Common mistakes

Taking one gel at 30 km "just in case".
Trying a new gel flavour on race day.
Using single-sugar glucose sources at 90 g/h, which can cause stomach distress.

Who needs different advice?

Diabetics need an individual plan with their clinician. Fructose malabsorption makes glucose-fructose blends uncomfortable; a dietitian can help.

Teenage runners should rely on normal food, and pregnant runners, people with kidney disease and anyone on regular medication should check their plan with a doctor or dietitian.

Products mentioned

Product	Size	Price (source, date)	Servings	R per serving	Sweeteners
32Gi Race High Intensity Sports Drink (900 g)	900 g	R470 (Dis-Chem Living Fit, 2026-10)	12	R39.17	None listed
Biogen Elite Carb Energy Gel, unflavoured (60 g)	60 g sachet	R44.99 (Dis-Chem Living Fit, 2026-10)	1	R44.99	None listed
Science in Sport (SiS) GO Isotonic Energy Gel (60 ml)	60 ml sachet	R45–R49 (Sportsmans Warehouse via PriceCheck, 2026-10)	1	R44.90	None listed
Maurten Gel 100 (40 g sachet)	40 g sachet	R74–R75 (goneoutdoor / The Athlete's Foot via PriceCheck, 2026-10)	1	R75.00	None listed
Biogen Liquid Energy Gel (60 ml, orange or strawberry)	60 ml sachet	R26.99 (Biogen (own shop), 2026-10)	1	R26.99	No artificial sweeteners listed

Educational information, not medical advice. Speak to a doctor, pharmacist or registered dietitian before using supplements if you are pregnant or breastfeeding, under 18, taking medication, or living with kidney, liver or heart disease. Prices were observed in October 2026 and are not offers.