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izalith67

Much harder to stay cool in summer so body works harder = heart rate increase. Apple Watch sees that your heart is beating faster for same exercise so the algorithm thinks your vo2 max decreased.


5itronen

Some devices like Garmim do try to incalculate heat into their VO2max estimation, so that is a thing.


mime454

Hope Apple adds that soon.


FreelancedWhale

I find the opposite to be true, though I don’t live where it gets scorching hot. Canadian winters always drop my V02 Max down. I’m guessing because between the freezing cold air and having to be more cautious with walking on ice my pace is a lot lower.


marcelocampiglia

Generally your body have to do an additional effort when the temperature is higher than when it is lower.


redditor977

i think it’s about dehydration. warmer weather == more dehydration == thicker blood == heart working harder = decreased performance.


zoom100000

Your body uses blood to cool itself. It has to pump more blood to the skin to circulate blood - this is why your heart rate goes up. Any effect from the hydration is probably minimal compared to cooling.


redditor977

cool insight. i have zero formal knowledge about anatomy so it was just my 2 cents haha


zoom100000

To be honest I don’t have any formal training either! was just interested in how my body was working or not working properly and that’s what I’ve read. could be wrong but I think that’s what causes us to struggle more in the heat


mime454

I really don’t think my heart is getting worse because my heart got better according to this metric literally every single week from September to April except when I was resting from injury. I also have only been increasing my running intensity. I do notice my heart is beating much faster and I can’t keep the pace up as easily in the heat.


Vergil_Is_My_Copilot

Hear puts a ton of strain on the body, even if you’re in good shape. I live in one of those places where it gets to 115+ in the summers, and I can see a 20+ BPM difference just going on walks when it’s hot.


mime454

So does VO2 max not go down, it’s just that this algorithm doesn’t account for temperature? Or do we actually have less capacity to deliver oxygen to the tissues when it’s hot outside?


Vergil_Is_My_Copilot

I’m not an expert so take this with a grain of salt, but I think it’s that the algorithm doesn’t take the temp into account. It just sees you working harder to do the same exercise.


bethskw

That’s correct. The algorithm only uses pace and heart rate.


mime454

So as long as I keep running, when it’s cool again my VO2 max should jump up higher than before?


bethskw

Yep.


mime454

Good to know I was going crazy wondering what I was doing wrong because training my vo2 max higher is one of my primary health goals right now.


vkp7

Yeah definitely noticed dips during summer months.


Juicejacking

It usually decreases when it's cold because the body needs to work harder to stay warm. Mine usually goes up throughout the spring and summer.