Hitting The Wall In Endurance Events

Ever hit the wall halfway through a race and wonder why your legs quit on you? That dreaded mid-race slump can crush your pace, focus, and motivation, but it doesn’t have to. With the right fuel, hydration, and training hacks, you can power past fatigue and finish strong.

Table Of Contents

• What Causes the Mid-Race Slump or “Hitting the Wall”?

• Are You Carb Loading Enough Before the Race?

• Are You Fuelling Early & Consistently During the Race?

• Could Dehydration or Electrolyte Imbalances Be Slowing You Down?

• Can Caffeine, Nootropics, or BCAAs Help Maintain Mental Focus?

• Is Your Training Preparing You to Sustain Race-Day Effort?

What Causes The Mid-Race Slump or “Hitting the Wall”?

The mid-race slump is a common experience in endurance events where athletes suddenly feel a sharp drop in energy, pace, or motivation. While it often feels like it appears out of nowhere, it is usually the result of physiological factors building throughout the race.

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“Hitting the wall” is most commonly associated with glycogen depletion, where muscle and liver carbohydrate stores become insufficient to sustain the required exercise intensity. As glycogen availability declines, the body shifts toward greater fat oxidation, which produces ATP at a slower rate and can limit performance at higher intensities. Reduced blood glucose can also affect the brain, contributing to central fatigue, impaired motor output and reduced motivation to maintain pace¹,².

Are You Carb Loading Enough Before The Race?

Your fuelling strategy starts well before race morning. Adequate carbohydrate intake in the days leading up to an endurance event helps maximise muscle glycogen stores and provides the foundation for sustained performance.

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Carbohydrate loading typically involves consuming 8-12g of carbohydrate per kilogram of body weight per day in the 1-2 days prior to prolonged endurance events lasting longer than 90 minutes³. This strategy increases muscle glycogen concentrations above normal resting levels, which can significantly delay fatigue during prolonged exercise.

Are You Fuelling Early & Consistently During the Race?

A common mistake athletes make is waiting until they feel fatigued to start fuelling. By that point, carbohydrate availability may already be declining.

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Current sports nutrition guidelines recommend 30-60g of carbohydrate per hour for exercise lasting 1-2.5 hours, and up to 90g per hour for longer events when multiple transportable carbohydrates (e.g., glucose/maltodextrin/cyclic dextrin and fructose) are consumed. These carbohydrates maintain blood glucose levels, spare liver glycogen and support high rates of carbohydrate oxidation during exercise¹⁻³.

Could Dehydration or Electrolyte Imbalances Be Slowing You Down?

Fluid losses during endurance exercise can gradually impair performance, particularly in warm environments. Even mild dehydration can increase cardiovascular strain and perceived effort. Aim for around 150-250mL of a carb‑electrolyte drink every 15-20 minutes to replace fluid and sodium losses⁴.

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A body mass loss of around 2% or more from dehydration has been associated with reductions in endurance performance in many laboratory studies. Reduced plasma volume increases heart rate, decreases stroke volume and can impair thermoregulation, which together increase physiological strain. Electrolytes such as sodium help maintain fluid balance, support nerve signalling and stimulate thirst, making them useful during prolonged exercise where sweat losses are high⁴,⁵.

Can Caffeine, Nootropics, or BCAAs Help Maintain Mental Focus?

Mental fatigue can play a significant role in the mid-race slump. Strategies that support alertness and perceived effort may help athletes maintain pacing and decision-making during long events.

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Caffeine is one of the most well-established ergogenic aids, with effective doses typically ranging from 3-6mg/kg body weight before or during exercise⁶. Caffeine enhances performance by reducing perceptions of fatigue and improving alertness. Some athletes also experiment with compounds often grouped as “nootropics” to support cognitive function, though evidence varies widely between ingredients. Branched-chain amino acids (BCAAs) have been proposed to influence the tryptophan-serotonin pathway which may help central nervous system fatigue⁷.

Is Your Training Preparing You to Sustain Race-Day Effort?

Nutrition can only support the performance your training has prepared you for. Conditioning the body through consistent endurance training improves both metabolic efficiency and fatigue resistance.

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Endurance training boosts mitochondria, blood supply and enzymes, helping your body produce energy more efficiently. It also enhances the capacity to oxidise both carbohydrates and fats during exercise, helping preserve glycogen stores¹,³. Long training sessions can also train the gut to tolerate higher carbohydrate intakes during exercise, allowing athletes to consume larger amounts of carbohydrate without gastrointestinal distress during races.

Key Takeaways
Hitting the wall isn’t inevitable, smart preparation makes all the difference. Carb load 8-12g/kg in the 1-2 days before your race, then fuel consistently during the event with 30-60g of carbs per hour for races up to 2.5 h, or up to 90 g/h for longer events using multiple carbs like glucose/maltodextrin/cyclic dextrin + fructose. Stay hydrated with around 150 mL of a carb‑electrolyte drink every 20 minutes to replace fluid and sodium losses. Pair this with caffeine (3-6mg/kg), if it agrees with you, for alertness and training that builds mitochondrial capacity and fat oxidation and you’ll give yourself the best shot to avoid the mid-race slump and finish strong.

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

Reference

1. D. Travis Thomas, Kelly Anne Erdman, Louise M. Burke. Position of the Academy of Nutrition and Dietetics, Dietitians of Canada, and the American College of Sports Medicine: nutrition and athletic performance. Med Sci Sports Exerc. 2016;48(3):543-568. doi:10.1249/MSS.0000000000000852.
2. Kerksick CM, Wilborn CD, Roberts MD, Smith-Ryan A, Kleiner SM, Jäger R, et al. ISSN exercise & sports nutrition review update: research & recommendations. J Int Soc Sports Nutr. 2018;15:38. doi:10.1186/s12970-018-0242-y
3. Burke LM, Hawley JA, Wong SHS, Jeukendrup AE. Carbohydrates for training and competition. J Sports Sci. 2011;29 Suppl 1:S17‑27. doi:10.1080/02640414.2011.585473.
4. American College of Sports Medicine. ACSM Position Stand: Exercise and fluid replacement. Med Sci Sports Exerc. 2007;39(2):377‑390. doi:10.1249/mss.0b013e31802ca597.
5. Sawka MN, Cheuvront SN, Kenefick RW. Hypohydration and human performance: impact of environment and physiological mechanisms. Sports Med. 2015;45(Suppl 1):51‑60. doi:10.1007/s40279‑015‑0395‑7.
6. International Society of Sports Nutrition (ISSN) Position Stand: caffeine and exercise performance. J Int Soc Sports Nutr. 2021;18(1):1‑23.
7. Davis JM. Carbohydrates, branched‑chain amino acids, and endurance: the central fatigue hypothesis. Int J Sport Nutr. 1995 Jun;5 Suppl:S29‑38. doi:10.1123/ijsn.5.s1.s29.

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.