Barometric pressure effect on performance

Its raining today here in the UK. A lot. And I feel pretty rubbish, like I can’t be bothered to ride my bike. A couple of colleagues said they felt the same and so I did a bit of digging into being ‘under the weather’. As it turns out, there is a fair bit of evidence that low barometric pressure can induce symptoms such as sleepiness, fatigue, low blood pressure, headaches and migraines. Fair enough - that’s a good reason to explain how I’m feeling - nothing to do with the current high training load. I was flying yesterday!

I figured I’d ditch the crit I’d been planning to do this evening, as I did’t fancy driving an hour+ each way after work, getting soaked/cold, then getting in really late and not being able to sleep. I don’t really like crits anyway and have a stage race at the weekend, so a rest/easy day is fine. I’ve been training really solidly the last few weeks too.

So I looked at my training diary to re-plan Wednesday/Thursday/Friday - a mini taper. I was about to write under today - “Rest (Mental fatigue)”. A marker for an unplanned rest day - not down to illness/legs. These days are dotted all the way back through my training diary over the last 3+ years.

Something clicked - I wondered if there’s a pattern here.
I checked up on the current air pressure - 1001mb and falling - quite low.

Then I looked back through at other instances of unplanned rest, cross-referencing with the air pressure from https://www.timeanddate.com/weather/uk/stockport/historic
and hey presto about 90% of these days had low pressure, usually under 1000 mb.

Well that’s interesting… I’d usually put them down to overtraining, life stress, oncoming illnesses etc., but those reasons didn’t stack up for quite a few of the dates.

Next, I looked at days where I failed workouts or scaled back what I had planned based on how I’d been feeling. This doesn’t happen particularly often, but on the days I picked out, the air pressure was more often than not on the low side or falling. One day in particular - I’d ramp tested after a solid block of training, expecting a bump in FTP but was 15W down… the pressure was 990 mb.

So could this affect things the other way I wonder? I looked for strong performances where I’d hit unexpected power PBs, done really good tests etc…
Consistently 1020 mb, 1030 mb!
And in a period around new year this year, where I felt invincible and was crushing tough workouts day after day… the air pressure was in the 1040s! Thinking back it felt like when Nate goes down to sea level and says it feels like cheating!

So what does this mean? The difference between the highest (1046 mb) and lowest (978 mb) is 7%. Which is huge. Temperature and humidity differences notwithshanding, that’s a 7% difference in air density, which is like the difference between Sea level and 1500-1800m altitude! There’s 7% difference in oxygen in the air between those two pressures. Of course that’s going to affect your power!

Should we bear this in mind when training - maybe lowering intensity a few % if we know the air pressure is low. switching workouts for something less aerobically taxing maybe?
Should we account for it in testing? If doing a ramp test on a very high or low pressure day could easily knock your FTP off by +/- 3% then that’s a lot - it could easily be a 20W swing for me, more for some higher power riders.

Presumably this affects some people more than others… and some people will live in places with more pressure fluctuations.

Has anyone else got any experience of this? Anedotal or otherwise. Or a detailed enough training diary to look at their spurious missed days, failed workouts, poor performances etc. that they couldn’t easily attribute to other factors? Or even better some actual evidence/articles etc? Or think I’m talking rubbish?

The URL further up has historic weather data for locations worldwide if anyone else wants to look into their own data.

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Will be interested to see what people have to add to this.

I have felt a bit rubbish all day, heavy legs even though not been riding hard and generally groggy. Did a 5km run at lunchtime to try and loosen legs but it didn’t work. Now bit of a headache and just fancy a kip.

Not diagnosed SAD but my mood and how I feel do appear to correlate very much with weather.

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I had a look, but no obvious correlation I can see with my good performances or workout failures.

And also, with each workout failure, I can usually think of at least one other factor (hard workout / recovering from injury / doing it early morning without enough fuel / doing it too soon after flying / etc) that could have contributed.

It’s an interesting theory, and makes a certain amount of sense as higher altitudes have lower air pressure, but I’d also beware of confirmation bias on this one.

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I was thinking the same thing a few weeks back - and looked up the normal range of air pressure (similar to what you identified - about +/- 3.5%) and then translated that into altitude difference.

My result is different than yours - a 7% change in atmospheric pressure corresponds to about 600m (2000ft) change in altitude.

A general rule of thumb is that VO2max (and all else equal, FTP) reduces about 7% for every 1000m gain. So 600m would be about a 4% reduction in FTP.

Definitely enough to mean the difference between successfully completing a tough workout at 100% vs. having to lower the intensity.

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My n=1: yes.

Afternoon storms or rainy days, I’m far more likely to get home from work, look at the calendar, look at the bike and think, “:scream: :nauseated_face: :face_vomiting:.” I haven’t done the kind of analysis you have, but I noticed the pattern a while bike.

When I recognized it, I started being more diligent about forcing myself onto the bike anyway with the promise of a potential out with Amber’s “give it 20 minutes” rule.

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You could be right on the altitude figures, I estimated very roughly from the tables here…

FTP doesn’t vary as much as air pressure. Eg, at Leadville, air pressure is 30% lower, but FTP about 20% lower.

I haven’t researched why - maybe due to breathing rate increasing to compensate for lower oxygen content…

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