I understand there's many different opinions on the importance of an individual's absolute VO2 max number. Personally how VO2 max trends over time is what is more interesting to me as I find it a good signal to track long term health and how much overall fitness you're gaining or losing over time.

If this is a topic you're interested in learning more about I've built out this list of factors that influence it as a starting point for anyone to learn more and do their own research. To make this easier I've broken this down by category, included a short plain english definition, and linked all sources (scroll to the right on the tables and you'll see the hyperlinks). I've removed a few from here as it was getting far too long and sorry I know the tables aren't great on mobile but I'll include the full resource in the comments.

Exercise

Factor	Impact	Study/effect	Plain English	Evidence rank
HIIT (long interval, high volume)	Increase	Wen 2019. Meta, 53 RCTs. SMD 0.50 to 2.48 vs control, 0.65 to 1.07 vs steady cardio	Intervals of 2 min+ are the only version that beats steady cardio	Strong
Detraining	Decrease	Zheng 2022. 21 athlete studies. Under 30 days ES −0.62 (−3.93%). Over 30 days ES −1.42 (−9.43%)	Under a month off costs about 4%, longer about 9%	Strong
Moderate continuous cardio	Increase	Wen 2019. Overall SMD 0.41 to 1.81 across populations	Steady cardio works, it is just less time efficient	Strong
Sprint interval training	Increase	Sloth 2013. 19 studies, 13 with VO2max data. g = 0.63 (0.39 to 0.87), +4.2 to 13.4%	Very short all out sprints reliably raise it	Moderate to Strong
Resistance training (alone)	Increase	Smart 2022. 37 studies, 22 pooled. +1.89 mL/kg/min (1.21 to 2.57) under 24 weeks. Null beyond 24 weeks	Small bump in over 60s, and only in shorter programs	Moderate

Nutrition & Supplements

Factor	Impact	Study/effect	Plain English	Evidence rank
Dietary nitrate / beetroot	No effect	Gao 2021. Meta, 73 studies, n=1,061. Submaximal VO2 −0.04 L/min (p<0.00001). VO2max not significant	Makes a given pace cheaper to hold. It does not raise your ceiling	Strong
Creatine	Slight decrease	Gras 2023. Meta, 19 RCTs, n=424. ES −0.32 (−0.51 to −0.12)	Adds body water, so the per kilo number dips slightly	Strong
Iron (when deficient)	Increase	Pasricha 2014. 24 RCTs, 18 for this figure. +2.35 mL/kg/min (0.82 to 3.88)	Fixing low iron raises it. This is correcting a deficit, not a boost	Moderate to Strong
Caffeine	No effect	Brietzke 2017. RCT, n=9. Time to exhaustion +18.7%, peak power +13%, VO2max unchanged	Helps you push harder. Much of the benefit is placebo	Moderate

Demographics

Factor	Impact	Study/effect	Plain English	Evidence rank
Age	Decrease	Fleg 2005. Baltimore Longitudinal Study, n=810. 3 to 6% per decade in the 20s and 30s, over 20% from the 70s	Decline accelerates with age, and faster in men from the 40s onward	Strong
Genetics (trainability)	Variable	Bouchard 1999. HERITAGE, n=481 across 98 families. Maximum heritability estimate 47%	Same training, wildly different response. It runs in families	Strong
Dehydration	Decrease	Cheuvront 2010. Mechanism review. Threshold is over 2% of body mass	Less blood volume to pump, and heat makes it worse	Moderate
Sex	Variable	Santisteban 2022. Review. 10 to 12% performance gap. Elite women about 10% lower per kg	Mostly oxygen delivery, meaning haemoglobin mass and heart size	Moderate
Immobilization / bed rest	Decrease	Saltin 1968 n=5, with McGavock 2009 follow up. −26% in three weeks	Three weeks flat on your back costs about what 40 years of aging does. Crazy.	Moderate

Lifestyle & Environment

Factor	Impact	Study/effect	Plain English	Evidence rank
Sedentary behaviour	Decrease	Eriksen 2016. n=16,025. No association among the highly active	Matters most if you are not already training hard	Moderate (observational)
Sauna bathing (habitual)	Increase	Kunutsor 2024. 2,012 men. +0.30 mL/kg/min per weekly session. Lee 2022 RCT +2.7 (0.2 to 5.3)	A small extra bump stacked on top of training	Moderate
Smoking	Decrease	Caci 2025. n=70, step test estimate. 38.8 vs 41.6 in never smokers	Lower aerobic ceiling. Whether quitting reverses it is untested here	Moderate
Altitude (live high, train low)	Increase	Wehrlin 2006. 10 elite orienteers at 2,500 m for 18 h/day over 24 days. VO2max 3,515 to 3,660 mL/min	Sleeping high builds more oxygen carrying red cells	Moderate
Heat acclimation	Increase	Waldron 2021. 28 articles. Hedges' g 0.42 cool, 0.63 hot. Lorenzo 2010 +5% cool, +8% hot	Plasma volume expands. Clearest when you are also tested in heat	Moderate

I'm 23, I have been smoking since I was 19. I was only smoking 1-2 cigarettes a day in all those years. More than that always made me weird in my lungs so I did not do that. Life is good, and I just decided to quit for a half marathon in December 2025.

Was smoke free from November 1025 - July 2026.

Did the half marathon in about 2:30 and it felt great. Somehow, was completely smoke free until June 2025 and somehow ended up smoking 1 cigarette at a graduation party. That was the relapse.

I am doing well in my life, making a lot of money after I graduated. I am even into a lot of sports, still running 2-3 times a week and cycling about 2-3 times a week + 1-2 gym sessions a week.

Somehow, post the relapse, I started enjoying them more. I convince myself that I ran about 20 km/week and cycle about 60-70km/week and gym, so it's harmless.

Today was the worst. I went on a long cycling ride, and the view was too good and smoked a cigarette. Coming back home, my HR had spiked all the way and I felt so bad about myself.

Help me debunk this positive/negative of excercise and smoking. Personal experiences will help.

Ignore typos, am really furious at myself as I just came back from that ride.

I can't just not jog on concrete since thats all there is around me, my running shoes are fine, ive been doing calf workouts AND making sure that my feet land more or less right below me while jogging instead of outstretched.

I thought all of this would prevent shin splints well enough but i still got them and now i gotta take it easy while I recover, so please give me some tips on how I can prevent this in the future.

20M here Not much to explain but u am kinda fit in sense that I am not much fat and not much slim ,I do gym 4 times a week but the thing is my full body is lean and in good shape except stomach,my stomach area is kinda have fat maybe ,not a huge but not visible too so I think 4 times a week and running everyday in morning can help me by removing my fat which is only on stomach like I can't believe my body fat is only on stomach but none else...so should I start running??will it help or what should I do

It’s a strange feeling. Bottom of feet start feeling spongy & vision gets slightly brighter. Only happens if I try to walk at 4mph for a while. But if I back down to 3mph until the feeling goes away, then I can bump it back to 4mph & be fine for the rest of the hour. Anyone else ever experience this? Maybe circulation issues?

I’m curious if walking about 4.5 miles 5-6 days a week is too much. I’m fairly skinny with a little fat around the torso, and am trying to have that lean look. I strength train 3-4 days a week, PPL split.

Just curious if I can get good size gains and lose fat with this regimen.

Is this considered hiit?

I’m wondering if what I’m doing is hiit. I’ve been attempting to improve my vo2 and I’m at a loss. My watch says my vo2 is roughly 26.
I’m inclined to believe it due to my interactions in capoeira and other sports.

How can I improve this?
As far as vo2, am I wasting time?

Disclaimer:
I understand the watch is not 100% accurate. It still helps me track with some consistency

Basic stats:
43m
6’2ft
180lbs

How I feel at different heart rates
Tracking with apple ultra 3

@~160bpm: breathing increases, speaking
@~170bpm: heavy breathing, a word or two
@~175bpm+: gasping, no words
@~183bpm I have puked on multiple occasions
it takes extreme will to go for very long
Desperately gasping

I’ve never been past 185. I’ve made real effort but so far 185 was highest.

Hill stats:
per segment
Distance: .1 mile
Climb: 100ft
Rough terrain

The exercise:
1 lap Lap = 2 segments
Segment 1 is up
Segment 2 is down
I do 3-5 laps (6-10 segments.) 5 days a week
After my laps is usually do an easy hike 3-5 miles. (After resting for 5-10 minutes)

Segment 1
Start segment 1: 135-140bpm
Halftime of segment: 155-160bpm (1:15)
End segment 1: 175-180bpm

Segment 2 begins no rest:
End lap 1: 140-145bpm
Lap 1 total time: 2:30

Lap 2 begins immediately no rest

**I’m usually in the 175bpm+ for 15-20sec + an additional however long it takes to lower.

The laps generally follow the same times and heart rate give or take 5 seconds.

When I’m going for a regular hike, I can easily do 15+ miles with zero issue. Often with zero rest depending on terrain.

I got a Rogue Echo Air Bike and doing HIIT. Long time natural bodybuilder. New to cardio. 33 year old male wanting to improve my V02 max for longevity.

Because there is resistance, my muscles get fatigued early and can’t go harder in terms of cardio anymore. My HR is like 150-160 only when doing air bike before getting tired and needing to stop.

Idk know my true max HR, but current detection is 201. I know I can probably go higher.

I did a quick jog/run and easily hit 190, cause there is less resistance.

So Air Bike literally prevents me from doing HIIT properly. I’m supposed to be in 90-95% right?

Is the air bike the problem or me? Should I just do regular running?

Hello, I see a lot of posts in the fitness communities about prioritizing recovery. Does that mean I shouldn't do my normal 1 1/2hrs of cardio a day? I want to gain muscle but I am also an endurance athlete and train daily to improve my performance. Am i overloading my body? I only do zone 2 so it really isnt physically taxing. I workout upper and lower twice a week and my core twice as well. They are spaced out and each muscle group gets atleast a day of recovery.

Hi there, 26 Female, 172cm, 140kg, Autism, ADHD, Depression, Anxiety, Sleep Apnea, PMOS, sinus tachycardia. I take Escitalopram, Omeprazole, Magnesium, medical cannabis and sometimes Ropinarole. Dont smoke cigarettes or drink often.

Today I started seeing a physio for help with an excersise plan that will work for me. We did a stress test, 6 minutes of walking laps, heart rate recorded at each minute. I started high as always, about 120bpm, but as I walked it dropped all the way down to 55bpm, it rose slightly when a person who wasn't my physio walked into the room, at 76bpm, but then back down as she left. The measurement when I was sitting back down was back to 112bpm.

My family has a history of heart problems and diabetes.

Why could this be? Is it bad?

I am 21 and have health anxiety, 2 months ago I was going through a lot of anxiety and my heart rate would spike up so I went to a cardiologist who ran tests and told me everything was fine, but I hadn’t started exercising and losing weight like now. 2 months later I’m jogging almost everyday and have lost almost 10kg, I don’t jog nearly as much distance as some people here. 3.5km average sometimes max 5. I have noticed since my resting heart rate in the 50s.

I did a 5k race tonight & was aiming to PR. It was in similar weather to the hyrox race in NYC i did in june, and I realize I had a pounding headache both times, probably because I was in zone 4/5.

I take a low dose of atenolol and recently learned it lowers your max heart rate which reduces exercise capacity. My speed in general is very slow, even though my strength and endurance are very good. It’s never added up for me, but I’m thinking my medication may be part of it now. So I’m just curious if there are others here on beta blockers who have noticed similar things?