Most runners breathe through their mouth because nobody ever told them not to. Switching to the nose is one of the few changes in running that costs nothing, needs no kit and shows up on race day. It also feels terrible for the first couple of weeks, which is why most people quit before it pays off. Here's how to get through that part.

Why bother

The nose slows the breath down. That's the point, not a drawback. A slower, fuller breath pulls the diaphragm into the work, keeps the heart rate lower at a given pace and stops the shallow panting that has you blowing up on the first hill. Over weeks it raises your tolerance for the build-up of carbon dioxide that creates the "I need air" feeling, so the same effort feels calmer.

It also makes you honest. You can't run an easy day too hard with your mouth shut; the nose simply won't let you. For most amateur runners that's the single biggest training fix available.

And in winter the nose warms and filters the air before it hits your lungs, which your chest will thank you for in

The four-week way in

Week 1: nose only when it's easy. Walking, warming up, cooling down, the first ten minutes of every run. Mouth closed. If you need to open it, you're going too fast, so slow down. This is the week you find out how much you've been mouth breathing without noticing.

Week 2: nose only for the whole easy run. Expect to be slower, sometimes a lot slower, and expect the urge to open your mouth to arrive around minute fifteen. Sit with it for thirty seconds before you give in; it usually passes. Keep interval and tempo days as they are.

Week 3: everything except the hard stuff. Easy runs, long runs and the recovery jogs between intervals are now nasal. You should notice the early-run urgency has gone and your easy pace is creeping back up.

Week 4: push the ceiling. Start your tempo runs through the nose and only open the mouth when you genuinely have to. Note the pace where that happens. That number will keep rising for months.

Race day stays mouth-and-nose. Nobody is winning a HYROX with their lips sealed on the wall balls. The goal is to make the nose your default and the mouth your overflow, not to

The rules

• If you have to open your mouth, you're going too fast for that session. Slow down rather than cheat.

• Blocked nose: use a strip or skip the nasal work that day. Don't force it.

• Don't try anything new in a race. Train it first.

• Practise off the road too. Five minutes of floor breathing after a run teaches the pattern faster than running does.

Where the strip fits

The nasal valve, the narrow bit just above your nostrils, collapses on hard inhales. For a lot of runners that's the real reason nasal breathing feels impossible at pace: not fitness, just airflow. A NEON strip holds the valve open mechanically, which takes the ceiling up and makes weeks two and three a lot less miserable. If you're not sure whether that's you, read do nasal strips actually work for sport, then try one on an easy run with your mouth shut.

Where to practise

Your run club's social run is the perfect place: a conversational pace, people to talk to, and a built-in test. If you can chat through your nose, you're doing it right. Pair that with Jacko's diaphragm session twice a week and in a month you'll wonder why you ever ran any other way.