Why Most Runners Get Pacing Wrong
The real reason you keep blowing up — and how to fix it
I can’t count how many times I’ve lined up for a race, felt amazing in those first few miles, and convinced myself I’d finally cracked the code on perfect pacing.
My legs felt light, the pace easy, the watch steady — this was going to be it, my best PR ever. Maybe a podium position for my age group. Maybe even first.
Then the halfway point hit. Breathing tightened. Legs turned heavy. The same pace that felt effortless now felt like a grind. By the last stretch, I was just hanging on.
Another race where I’d gone out too fast and paid the price. Sound familiar?
It happens to new runners and seasoned racers alike. We think pacing is just about watching the clock or hitting the “right” numbers. But pacing isn’t a spreadsheet—it’s physiology.
It’s energy systems, fuel use, heat management, and patience stacked together.
Get it wrong, and the wheels fall off.
Get it right, and you finish strong. Sometimes even faster than you thought possible.
“Most races are lost in the first mile, not the last.” — Jack Daniels
Struggling with pacing? Let’s fix it. Book a FREE Discovery Call and find out how coaching can help you run stronger — and finally stop blowing up halfway.
What Pacing Really Means
Most runners think of pacing as just a simple number - minutes per mile. But that’s only the surface.
Pacing is really about what’s happening inside your body as you move: how much fuel you’re burning, how much oxygen your muscles are using, how much heat and waste you're generating.
The same pace can feel completely different depending on variables.
Run a 10:30 mile at the start of a long run, and it might feel like jogging. Run that same 10:30 mile at the end of a marathon, and it can feel impossible to maintain. The clock hasn’t changed, but your physiology has.
That’s because pace is the result of several important factors:
Energy systems — At easier efforts, your body leans more on fat metabolism, which is slow but sustainable. As intensity rises, you burn blood sugar and glycogen faster — and those are limited. Go too hard too soon, and you’re burning through reserves you’ll need later.
Cumulative fatigue — The longer you run, the more stress stacks up. Muscle fibers get micro-damage, body temperature climbs, and lactate builds. Even if your pace stays constant, the strain is rising over time.
Heat and heart rate drift. As core temperature rises, your heart has to work harder to circulate blood and cool you down. That means your heart rate climbs over time at the same pace — a phenomenon called “cardiac drift.”
Perceived effort — Your brain processes all this and tells you how hard it feels. This is why “effort drift” happens. Holding the same pace feels harder and harder as the miles build, because your brain is sending signals to rest.
This is why great pacing isn’t about discipline alone. It’s a skill. You have to learn how your body responds at different speeds, in different conditions, and over different distances.
Why Runners Blow Up
Most runners have experienced a blow up at some point — heart rate spikes, breathing is all over the place, and legs refusing to cooperate. No matter how much you want to hold the pace, your body won’t let you without redlining even harder.
You’ve probably felt this: by mile 12, your watch says the same pace, but your body feels like it’s sprinting uphill.
Pacing is keeping your systems in balance. Blowing up is what happens when you push them past the limit.
Think of your body like an engine: it can hum smoothly for hours when everything is in balance — but press too hard on the accelerator, and problems start stacking up fast.
Here’s how it plays out:
Running out of fuel. Push too hard too soon, and you burn through blood sugar and glycogen like a racecar. They’re premium fuels — fast and powerful — but they don’t last long. Fat is your real all-day diesel. It burns steadily, but more slowly and only at lower intensities. Empty the high-octane tanks too quickly, and suddenly the same high pace feels impossible. That crash is what runners call hitting the wall.
Cumulative wear and tear. Even the best-tuned engine can’t run forever without heat and friction building up. In your body, that’s micro-damage in muscle fibers, rising lactate, and the slow grind of fatigue. Keep pressing the pedal, and the system eventually gives.
Overheating. Just like an engine redlines when the radiator can’t keep up, your body overheats when it can’t shed heat fast enough. Core temperature rises, blood shifts to the skin, and heart rate increases to meet the extra demand. Cardiac drift is your “engine fans” in overdrive — but you can’t run in the red forever.
Warning lights in the brain. Modern cars have sensors to prevent total failure. Your brain does the same. As fuel drops, heat rises, and fatigue stacks up, your “dashboard” flashes with rising effort. That voice telling you to slow down isn’t weakness — it’s your central governor keeping you from a complete shutdown.
The mistake most runners make? They treat pacing like flooring it on an open road, assuming they’ll just hold on until the finish. But real pacing is more like driving a long mountain pass: you have to watch the gauges, shift gears, and manage the engine so it lasts the whole trip.
Blow-ups happen when you ignore those limits. The key is learning to read the signals early and keep the system running in balance.
How to Train Pacing
There’s one more piece to consider when training — the one that connects everything: oxygen.
Every system under the hood depends on how well you can deliver and use it.
Lungs — take in air and move oxygen into the blood; greater volume and efficiency create more supply with fewer breaths.
Heart — pumps oxygen-rich blood with every beat; a stronger stroke volume means more delivery with less work.
Blood vessels — transport oxygen throughout the body, expanding networks and redirecting flow to the areas that need it most.
Muscles — rely on mitochondria to use oxygen efficiently, converting fat and sugar into steady, usable energy for movement.
Brain — monitors oxygen balance constantly, raising effort signals and forcing slowdowns when delivery and demand fall out of sync.
Run too fast, and oxygen demand outruns supply. Fat — your steady, all-day fuel — becomes inaccessible, so your body chews through blood sugar and glycogen instead. Waste builds up, muscles burn, and rising heat diverts blood toward the skin, leaving less oxygen reaching the working muscles. Heart rate spikes as your body scrambles to keep up with the demand, but once you’re above threshold, the redline won’t hold.
That’s the physiological version of blowing up.
Training pacing is more than discipline or strategy — it’s about teaching your body to manage oxygen effectively.
Start easier, finish stronger. Open the first 20–50% of a run at an almost too-easy pace, then finish faster. This protects your high-octane fuel (glycogen and blood sugar) early and teaches your engine to stay efficient when fatigue builds. You’re upgrading fuel management and efficiency under load.
Run by breath, not just by watch. Pace shifts with terrain, and heart rate drifts with heat, fatigue, or stress — but breathing is a direct readout of oxygen demand. Training in this way enhances your brain’s ability to gauge and control effort in real-time. Think of it as your dashboard:
If you can speak in sentences, you’re in aerobic cruising (all-day effort).
If you’re down to short phrases, you’re near/at threshold (challenging but sustainable).
If you’re gasping, you’re redlined (seconds or minutes remain, not miles).
Train steady hard, not all-out*. Intervals and tempos just under race pace let you run hot without blowing the engine. This strengthens your aerobic system at high output, raises your threshold, and teaches your engine to stay smooth at higher intensity. You’re upgrading stamina and control at speed.
Build your VO₂ engine*. Shorter, faster repeats near max effort increase how much oxygen your heart, lungs, and muscles can actually take in and use. It’s like installing a bigger intake and stronger pump — raising your aerobic ceiling so every other pace feels easier.
Simulate race stress. Fuel, hydrate, and sometimes train in the heat. Heat diverts blood away from muscles, and low blood sugar spikes oxygen demand — the same stressors that cause mid-race breakdowns. Training here upgrades your cooling system and teaches the engine to stay balanced under pressure.
*These more intense workouts should be limited to once a week
The real skill of pacing is managing oxygen supply and demand so the engine stays balanced from start to finish. That’s what lets you tap into fast fuels when you need it, burn fat steadily in the background, and keep your brain’s “dashboard lights” from flashing too soon.
Train this way, and you stop guessing with numbers. You learn to feel the effort, control the burn, and arrive at the finish line with enough left to push — instead of blowing up halfway.
What about you? Have you ever blown up in a race or learned a pacing trick that changed the way you run? Drop a comment below and share your experience.
The runners who finish strong aren’t the ones who hammer every mile — they’re the ones who know how to manage their engine. Pacing is more than discipline alone. It’s about balancing oxygen, fuel, heat, and control so your body can go the distance.
Train that skill, and suddenly the same miles feel smoother and sustainable. That’s what turns races from survival mode into performances you’re proud of.
Do you tend to go out too hot, or hold back too much? Where could smarter pacing change your next race?