What Went Wrong In Your Marathon? 5 Fixes For A Stronger Next Race

Ever crossed the marathon finish line wondering what went wrong? You trained hard, fuelled up and showed up ready but something didn’t click. Cramping, stomach upset, blisters, or running out of steam, almost every runner has experienced a race that didn’t go to plan. The good news? Every setback is a chance to learn. Let’s unpack five common marathon mistakes and how to fix them, so you can line up next time feeling informed and ready.

Did I Start Too Fast?
Was My Fuelling Plan Right for Me?
Did I Hydrate Properly?
Did My Training Match the Race Demands?
Was My Gear Helping or Hurting Me?

Did I Start Too Fast?

A common marathon pacing mistake is starting too hard. Starting too fast burns glycogen faster than your body can replace it, leaving you depleted in the later stages of the race (1).
The early race adrenaline can make the first 5-10 km feel effortless, but over 42km that pace can lead to early fatigue.
Control your start with effort and pace, so you have fuel left for the finish

What to try for your next race → Start the first few kilometres strong and enjoy the crowd’s energy, but monitor whether your pace and heart rate are sustainable for the full race.

Was My Fuelling Plan Right For Me?

Under-fuelled? Many runners don’t take on enough carbohydrates per hour to sustain energy. During a marathon aim for 60-90g carb/hour (2-5).
Over-fuelled? Some runners overdo it, chasing the high-carb trend their gut can’t handle, which can lead to bloating, nausea or the dreaded mid-race toilet stop (5).
Did you try new gels or drinks on race day that your gut wasn’t used to and paid the price?
Too many carbs at once? Large amounts of carbohydrates, especially without adequate fluid, can cause gastrointestinal issues during endurance exercise (2).
Some athletes are sensitive to fructose, gluten or artificial sweeteners, which can cause gut discomfort (6). Choose products your gut tolerates.

What to try for your next race → Practice your fuelling strategy in training. Stick with familiar products. Spread your carb intake evenly aiming for 60-90g/hour. Pair gels with water. Gradually train your gut to tolerate higher carbs so race day feels smooth, not stressful.

Did I Hydrate Properly?

Drank too little. Low fluid intake can lead to dehydration, fatigue and overheating (7).
Drank too much plain water. Plain water dilutes sodium and can cause hyponatremia. Include electrolyte in your fluids to avoid imbalance (8).
Inadequate sodium intake? Aim to replace 60-80% of fluid losses and 300-800 mg sodium per hour (up to 1000-1500 mg in hot marathons) to stay hydrated and maintain performance (9).
Relied on aid stations? You might only get small sips, miss the electrolyte table, or end up with drinks your gut doesn’t tolerate.
Practice hydration in training to find your ideal mix of water + electrolytes under different weather conditions.

What to try for your next race → Aim for 150-350mL of an electrolyte mix with some carbs every 15-20 minutes to stay adequately hydrated (7). Consider running with a handheld flask, hydration belt or vest.

Did My Training Match The Race Demands?

If your long runs, race-pace work or tempo runs weren’t sufficient, race day will expose the gap.
You might have neglected “race-specific” workouts, replicating pacing, fuelling and terrain.
High mileage alone isn’t enough without threshold or speed work.
Additionally, overtraining or skipping a proper taper can leave you starting the race fatigued instead of fresh.

What to try for your next race → Build training that mirrors race demands. Include long runs, pace and terrain-specific sessions. Practise fuelling and plan a proper taper so you arrive rested and ready to perform.

Was My Gear Helping or Hurting Me?

New or untested shoes may cause blisters, hotspots or altered biomechanics under fatigue.
The wrong socks can rub, create friction, or steal energy through irritation.
Clothing choice → materials that don’t wick or ventilate well can exacerbate chafe or heat stress.
Accessories like hats, cooling headbands , hydration belts and vests should be tried in training so nothing surprises you on race day.

What to try for your next race → Test all your gear in training; shoes, socks, clothing and accessories so everything feels comfortable and familiar on race day.

Take-Home Message

Even a tough marathon is valuable feedback. Reflect on pacing, fuelling, hydration, training and gear. Adjust one or two before your next race and you’ll be lining up smarter, stronger and ready to run your best.

Ash Miller
Dietitian and Nutritionist (Masters)
Bachelor of Physical and Health Education
Instagram: @ashthomo_nutrition

References:

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Burke LM et al. Carbohydrates for training and competition. J Sports Sci. 2011;29(Suppl 1):S17–27.
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Cao W, He Y, Fu R, Chen Y, Yu J, He Z. A Review of Carbohydrate Supplementation Approaches and Strategies for Optimizing Performance in Elite Long-Distance Endurance. Nutrients. 2025 Mar 6;17(5):918. doi: 10.3390/nu17050918. PMID: 40077786; PMCID: PMC11901785.
Sports Dietitians Australia. Fluids in sport. Canberra: Sports Dietitians Australia; 2015.
International Society of Sports Nutrition. Position stand: Exercise and fluid replacement. J Int Soc Sports Nutr. 2010;7(1):7.
Sawka MN, Burke LM, Eichner ER, Maughan RJ, Montain SJ, Stachenfeld NS. (2007). American College of Sports Medicine position stand. Exercise and fluid replacement. Med Sci Sports Exerc, 39 (2), 377-90.

Disclaimer:
The content in this blog is for general information only and is not a substitute for professional medical advice, diagnosis, or treatment. Always speak with your doctor or allied health team before changing your diet, exercise, or taking supplements, especially if you have a health condition or take medication. Please use this information as a guide only. Aid Station doesn't take responsibility for individual outcomes.