The pattern almost every beginner experiences
You head out for a run, feeling reasonably good. The first kilometre goes by without too much difficulty — manageable, even enjoyable. You think: maybe today will be a good one.
Then kilometre two arrives. Still okay, though the effort is noticeably higher. By kilometre three, something has shifted dramatically. What felt manageable now feels like survival. Your lungs are working hard. Your legs have gone heavy. You slow down significantly, or you have to stop.
What happened? You started at the same pace all three kilometres. Why did the effort feel so completely different?
What's happening physiologically
Two things happen at the start of every run that create this illusion of easiness:
Adrenaline and sympathetic arousal. The nervous system's anticipation of exercise triggers a stress response — adrenaline is released, heart rate begins to rise before you even take your first step, and the body mobilises energy reserves. Pre-run arousal can change how the opening minutes feel. You feel capable of more than you sustainably are.
Oxygen uptake still settling in. Even at what feels like easy pace, oxygen uptake takes time to rise toward steady state when exercise begins, so the opening minutes can feel different from the same pace later. The aerobic energy system — the one that can sustain effort for extended periods — has not yet fully ramped up to meet demand.
By kilometre two to three, the adrenaline has settled, the aerobic system is bearing the full load, and you are feeling the real cost of the pace you have been running. If that pace was too fast for your current fitness level — which is almost always the case for beginners who start based on how the first kilometre feels — the reckoning is sharp.
How to prevent it
The fix is conceptually simple and behaviourally difficult: start deliberately easier than your first-minute instinct suggests, using conversational effort as the guide.
This goes against every instinct. The first minute feels easy, your body wants to run faster, and restraining yourself requires deliberate effort. But this restraint is the most consequential thing you can do for the quality of the run overall.
A practical target: in the first five minutes of any run, you should be able to speak in complete sentences with minimal effort. If you cannot, you are going too fast. Slow down, even if it feels embarrassingly slow.
Cadence as an anchor
One of the useful properties of running with a cadence target is that it provides an objective anchor for the start of a run. Instead of judging pace by how it feels — which is unreliable for the first kilometre — you have a rhythmic reference that stays constant regardless of how energised the adrenaline makes you feel.
A cadence reference can help you notice when your rhythm changes, but pace still depends on Stride and terrain — use the beat as one anchor alongside easy effort. When the adrenaline surge makes you want to run faster, the beat stays at the same tempo, giving you something to notice the drift against.
The payoff: by kilometre three, the effort feels even. By the end of the run, you have something left — and the run has been better in every kilometre than if you had burned through your reserves in the first one.
The best kilometre of the run
Here is a simple heuristic for good pacing: the last kilometre should feel like the best kilometre of the run. Not the easiest — the best. You should be finishing with a sense of rhythm and control, not with the desperate sprint to get it over with.
If your final kilometre always feels like survival, you are starting too fast. Adjust the first kilometre until the last one starts to feel different.
