Warming up and cooling down get bundled together as one habit, as if they were two halves of the same thing. They are not. One has a clear and immediate effect on how you run; the other does something quite different from what most people believe. Worth separating them.
What a warm-up actually does
Warming up raises muscle temperature, and warm muscle behaves measurably differently from cold muscle. It contracts and relaxes faster, it is more compliant, and nerve conduction speeds up. Blood vessels in the working muscles dilate, so oxygen delivery is already elevated when you start rather than lagging behind. Joints move more freely as the fluid within them becomes less viscous.
The practical result: the first kilometre feels far better, and — more importantly — you can hit the correct pace in a hard session from the first repetition instead of spending the first two finding it. For a race, or any threshold or interval session, this is the difference between a good session and a wasted one.
On injury prevention, be a little careful about the claims. Structured warm-up programmes have reduced injury rates convincingly in team sports with a lot of cutting and jumping. For steady-state distance running the evidence is thinner. The strongest honest case for warming up is performance and comfort; injury reduction is plausible and probably real, but not as well established for runners as it is often stated to be.
A warm-up that works, in four parts
1. Raise (5–10 minutes)
Easy jogging, or brisk walking if you are newer to running. Genuinely easy — the aim is warmth, not fatigue. You should not feel you have done anything.
2. Mobilise (3–4 minutes)
Dynamic movement through the range you are about to use: leg swings forwards and sideways, walking lunges, hip circles, ankle rocks. Movement, not held stretches.
3. Activate (2–3 minutes)
Wake up the muscles that tend to stay quiet: glute bridges, monster walks, calf raises. Twenty seconds each is enough.
4. Potentiate (2–3 minutes)
Four to six strides — 20 to 30 seconds building to roughly the pace of the session ahead, with a full walk-back recovery. This is the part almost everyone skips and the part that most changes how the first hard rep feels.
Total: about fifteen minutes before a hard session or race. Before an easy run, the first ten minutes at a genuinely slow pace is the warm-up, and that is fine.
One thing to avoid before running
Very long static stretches — more than about 60 seconds on one muscle — temporarily reduce force production, by roughly 4 to 5 percent. Shorter holds are close to harmless: under 60 seconds the effect is around 1 percent, and it largely disappears once you follow the stretching with drills and strides. So there is no need to fear a 30-second stretch before a run — just do not spend several minutes hanging in long holds and then expect to race. Save static stretching for afterwards or a separate time of day, and keep the pre-run work dynamic.
Cooling down: what it does and does not do
Here is where honesty is more useful than tradition. Cooling down does not appear to prevent next-day muscle soreness, and the evidence that it prevents injury is weak. The idea that an easy jog “flushes out lactate” is also outdated — lactate clears within roughly an hour regardless, and it was never the cause of the soreness you feel two days later anyway.
So why do it? Because it does something more mundane and more immediate.
- It stops you feeling awful right afterwards. During hard running your leg muscles help pump blood back to your heart. Stop dead and that pump stops while your vessels are still dilated, blood pools in your legs, and light-headedness follows. Five minutes of easy jogging or brisk walking prevents that.
- It brings your nervous system down. A gradual transition from hard effort to rest settles heart rate and breathing more comfortably than an abrupt stop.
- It creates a window for the mobility work you would otherwise skip. Warm muscle is the best time for static stretching, and being already stopped and warm is the easiest time to do it.
What a cool-down looks like
Five to ten minutes of easy jogging or walking, until your breathing is conversational again. Then, if you want, five minutes of static stretching for calves, hip flexors, quads and hamstrings — useful for maintaining range of motion over time, though not for preventing soreness.
The short version
Warm up properly before anything hard — it directly improves the session. Cool down briefly because it makes the next twenty minutes more pleasant and gives you a slot for mobility work. Do not skip either, but do not expect the cool-down to save you from soreness. What actually reduces soreness is sensible progression, sleep and consistency.