Energy is the quiet currency of every training run, Parkrun, and race day. You can be well trained, perfectly hydrated, and wearing the lightest shoes on the market, yet still feel your legs turn to treacle at an awkward moment. This article explores why that happens, how the brain and muscles jostle for fuel, which surprising food and drink choices can help or hinder, and why pre-run rituals are more than superstition. If you’ve ever wondered why a half marathon feels buoyant while a full marathon can unravel at mile 20, you’re in the right place.

Why runners “hit the wall”: the physiology behind the slump

Most distance runners meet “the wall” sooner or later: pace drops, concentration wobbles, and each mile feels twice as long as the last. What actually causes that sudden slide?

The body’s limited fuel tank

Your muscles and liver store carbohydrate as glycogen, a readily accessible fuel for moderate to hard efforts. At typical marathon intensity, those stores have a ceiling: think roughly 90 minutes to 2 hours of running before the tank begins to run low. Once glycogen dwindles, your body leans more heavily on fat oxidation. That switch keeps you moving, but fat is slower to convert into usable energy, so pace and power suffer.

What depletion feels like

As glycogen dips, you may notice heavy legs, a rising rate of perceived exertion at a pace that felt comfortable earlier, and a creeping mental fog. The brain runs largely on glucose; when availability tightens, decision-making and motor control can feel less sharp—exactly the wrong time to be navigating a crowded water station or a blustery stretch along the seafront.

Why pacing and conditions matter

The harder you run early on, the faster you burn through your stores. Hills, headwinds, and heat (or an unseasonably warm 18–20°C day) all raise energy cost. Cold weather can do its bit too, as your body expends more to stay warm. A modestly conservative start, especially over distances longer than 10 miles, preserves glycogen for the late miles where it’s needed most.

The role of pre-run preparation

Glycogen availability isn’t just about race-day effort. In the 24–48 hours before a long effort, consistent carbohydrate intake supports fuller stores. Arriving at the start line under-fuelled—after a rushed breakfast or a light supper—stacks the odds against you, even if your training has gone perfectly.

What this means for your training week

If you occasionally include steady long runs with a deliberate negative split (slightly easier first half, slightly stronger second half), you’ll learn how to ration energy without staring at your watch every minute. Practise drinking little and often, wear layers suited to the forecast (so you’re not burning energy shivering), and keep your early miles honest. You’re teaching your body—and your judgement—how not to flirt with the wall in the first place.

Brain versus muscle: the tug of war for energy

It’s tempting to imagine energy as a single pool that simply drains away as you run, but the reality is far more complex. Your brain and your muscles compete for the same limited resources, and understanding this rivalry helps explain both physical fatigue and mental lapses during long efforts.

The brain’s demand for glucose

Even at rest, the brain consumes a sizeable portion of the body’s glucose supply. When you add prolonged exertion, the demand from the muscles soars, yet the brain still insists on its steady stream. If glucose drops too low, the brain quickly sends signals of fatigue, often long before muscles are truly empty. This protective mechanism is one reason you may feel exhausted or foggy even when you technically still have some energy in reserve.

Signs of mental fatigue on the run

Have you ever struggled to do simple maths while checking your pace, or felt clumsy navigating a crowded section of road late in a half marathon? These lapses are symptoms of the brain’s reduced fuel supply. Unlike muscles, which can eventually adapt to burning more fat, the brain has a narrower preference for glucose.

The role of quick-release fuels

Portable fuels such as sports drinks, fruit, or a running energy gel provide the glucose your brain craves. They can sharpen concentration, restore rhythm, and give you back a sense of control in the later miles. Interestingly, research has shown that even rinsing a carbohydrate solution in the mouth—without swallowing—can trigger receptors that reduce perceived effort. This suggests that part of the benefit is psychological as well as physiological.

Training the brain and body together

Just as muscles adapt to training, the brain can be conditioned too. Long sessions that include fuelling practice help your mind learn what to expect and reduce anxiety about the “low patch” many runners dread. Some athletes include mental strategies—such as visualisation or chunking distances into smaller goals—alongside nutritional preparation to balance both brain and body needs.

Unusual energy sources athletes experiment with

When people think of fuelling for endurance sport, the usual suspects come to mind: bananas, flapjacks, isotonic drinks, or the occasional running energy gel. Yet athletes, both recreational and elite, have tried some rather surprising energy sources over the years. Some have stood the test of time, while others are little more than quirky experiments.

Everyday foods on the race course

It’s not uncommon to spot runners grabbing handfuls of jelly babies from a supporter, or cyclists pocketing jam sandwiches on long rides. These quick, sugar-rich snacks offer a familiar taste and a rapid source of carbohydrates. Some UK marathons even provide sweets at official stations, a nod to both tradition and practicality.

Old-school remedies

Before purpose-made sports products became mainstream, endurance athletes relied on whatever was portable and calorie-dense. Raisins, malt loaf, and even digestive biscuits have all made appearances during long runs. The appeal is partly nostalgia: these are foods many grew up with, easy to find in any local shop.

The savoury alternative

Sweet fatigue can set in after hours of sugary snacks. Some athletes combat this with savoury choices such as salted crisps, pretzels, or mini pork pies during ultra-distance events. While perhaps less elegant than a packaged gel, they provide salt as well as energy, helping maintain balance in challenging conditions.

The unconventional choices

Stories abound of unusual mid-race snacks: flat cola carried in a flask, rice pudding sachets, or even mashed potatoes wrapped in foil for ultra-marathons. While these wouldn’t suit everyone, they highlight the individuality of fuelling. What works wonders for one runner might leave another searching for the nearest portable loo.

Why experimentation matters

The takeaway is that there’s no single “correct” fuel. Training runs provide the chance to test unusual options and decide what feels comfortable. While engineered products like running energy gels are convenient and predictable, sometimes the comfort of a familiar food—or the novelty of something different—can be just as powerful a performance boost.

What elite athletes avoid for better performance

It’s easy to imagine elite athletes fuelling on the most exotic or high-tech products available, but often their choices are as much about what they don’t consume as what they do. Small missteps in nutrition can quickly sabotage performance, so caution shapes much of their approach.

The problem with heavy meals

Rich, fatty, or bulky foods are usually avoided in the hours before competition. A fry-up might be a weekend treat, but before a race it risks sluggish digestion and stomach discomfort. Elite runners tend to favour lighter, carbohydrate-rich meals that top up glycogen stores without weighing them down.

Foods that cause digestive distress

Anything likely to ferment in the gut or cause bloating is kept well away from the race-day table. High-fibre foods such as beans, lentils, or certain vegetables are limited, even though they are staples of a balanced diet at other times. The same goes for spicy meals, which can upset sensitive stomachs during exertion.

Hidden pitfalls in “healthy” snacks

Even wholesome-sounding options can backfire if timed poorly. Yoghurt, milkshakes, and creamy desserts provide protein and calcium, but the dairy content can prove troublesome under the jostle of running. Similarly, sugar-free sweets or gums containing sorbitol or xylitol are notorious for prompting digestive urgency—hardly ideal mid-race.

Drinks with a sting in the tail

Caffeine is widely used by athletes, but too much can lead to jitters, dehydration, or a racing heart. Alcohol, of course, is strictly avoided close to competition, as it interferes with hydration and recovery. Fizzy drinks are another trap; while flat cola is sometimes used late in events, carbonation before or during running risks uncomfortable bloating.

Why exclusion is as strategic as inclusion

By steering clear of high-risk foods, athletes maintain predictability and control. Products like a running energy gel may feature in their toolkit, but they’re carefully integrated into a wider plan that minimises potential disruption. Ultimately, knowing what not to eat or drink is just as vital as choosing the right sources of fuel.

The psychology of fuelling rituals

Nutrition may fuel the body, but rituals fuel the mind. Many athletes swear by a set routine before training or competition, and while some choices may seem trivial, the psychological impact can be profound. These patterns provide a sense of control, stability, and confidence in a setting that is often unpredictable.

Comfort in routine

For some, it’s the same breakfast before every long run—porridge with honey, a slice of toast, or a particular brand of sports drink. The predictability removes uncertainty, allowing focus to shift from “Will this sit well?” to “How fast can I run today?” By weaving in familiar fuels like a banana or even a running energy gel at a particular point, athletes reinforce confidence through repetition.

Symbolic triggers

Rituals are not purely practical. They also serve as symbolic markers that signal “race mode” or “serious effort.” Tearing open a packet at the 10-mile point, sipping a set drink at a specific marker, or even pocketing a lucky snack wrapper can act as a cue that progress is being made. These small actions build a rhythm, making a daunting distance feel more manageable.

The placebo effect in practice

The belief that a fuelling strategy will work is often as important as the physiological benefit itself. Athletes who trust their plan tend to feel calmer, experience less anxiety about fatigue, and push through rough patches with greater determination. Even the simple act of tasting sweetness—whether from a sports drink or a running energy gel—can trigger neurological responses that reduce perceived effort.

Building resilience through practice

Repeated rituals in training help lock in these benefits. Athletes who replicate their pre-race breakfast or practise fuelling at the same intervals during long sessions are rehearsing not only digestion but also mindset. Come race day, their mental script is already written, providing reassurance when nerves are high and the unexpected looms.

Conclusion: energy as both science and story

Athletic performance isn’t just a tale of training plans and miles logged—it’s also shaped by how energy is managed, shared, and even believed in. The wall reminds us that physiology has limits; the brain’s hunger for glucose shows that focus and clarity are as fragile as leg muscles; unusual snacks reveal that individuality matters; food choices highlight that exclusion is as strategic as inclusion; and rituals remind us that belief itself is a kind of fuel.

The next time you lace up for a long run or a demanding event, remember that energy isn’t only stored in your muscles or supplied through a packet—it’s also in the choices you make, the confidence you build, and the rituals that reassure you when the miles begin to weigh heavily. So, what if your strongest source of power lies not just in the gel you carry, but in the trust you place in your own preparation?

Surprising Insights into Energy and Athletic Performance