Here’s a 2015 Mayo Clinic study. You’ll see the numbers, but also notice how this is considered Cardiorespiratory Fitness. The logical conclusion is otherwise. Keep reading.
VO₂ max is often defined as the maximum amount of oxygen the body can consume during exercise. It’s widely regarded as the gold standard of cardiorespiratory fitness. Many popular fitness influencers—Peter Attia, Rhonda Patrick, and others—treat VO₂ max as a direct measure of your heart and lungs.
But after years of training and experimenting, I’ve come to a different conclusion: VO₂ max isn’t primarily a cardiorespiratory function—it’s a muscular one
Why I Questioned the Standard VO₂ Max Narrative
Most experts agree you need two to four hours of Zone 2 cardio per week to improve your VO₂ max. Who has that kind of time? Others promote the Norwegian 4×4 protocol.
My VO₂ max is far beyond what these methods would predict.
- 30-33 years old: In chiropractic college, I tested at 47. At the time, I did no cardio, only low-rep weightlifting.
- Today @ 49: My VO₂ max is 63.5.
My current cardio volume? Minimal. I do the Norwegian protocol, three sets of four minutes, once a week. On another day, I perform eight short sprints (20 seconds each with 1:40 rest). Combined, that’s less than 15 minutes of “cardio” a week.
So how did my VO₂ max climb so high?
The “Aha” Moment: VO₂ Max is About Muscle Oxygen Use
A YouTuber named Tony from I Am Longevity connected the dots for me by talking about motor units. That’s when I realized: VO₂ max isn’t measuring your heart and lungs—it’s measuring how much oxygen your muscles can consume.
The legs are the largest muscles in the body and also the most oxygen-hungry. Unlike the chest or arms, leg muscles are built for endurance. That means they only recruit a fraction of their fibers during normal activities like walking or cycling. This efficiency explains why you can walk for hours but can’t bench press for hours: upper-body muscles recruit almost all their fibers with each contraction, while legs conserve most of theirs.
To truly max out oxygen consumption, you need to recruit every fiber in those massive leg muscles, which is why the Norwegian is better than zone 2. But to get to the more muscle fibers, it requires extremely intense, high-rep leg work.
My Training: 50-Rep Single-Leg Squats
Here’s what I believe made the difference:
- Once every two weeks, I perform single-leg squats with heavy weight to absolute failure: 50 reps per leg.
- Inspired by Mike (and Ray) Mentzer, Arthur Jones, and Tom Platz, I push very deep into failure.
- By the 20th rep, my legs burn. By 30, standing is hard. By 40–50, I’m deep into oxygen debt.
This style of training forces nearly every motor unit in the legs to fire, creating an oxygen demand that standard cardio can’t match. In my opinion, this is what pushed my VO₂ max into the 60s—not the small amount of weekly cardio.
Why Single-Leg Squats?
As a chiropractor, I’m aware of the spinal compression and disc stress caused by heavy bilateral squats. Single-leg squats minimize that risk while allowing for deep muscle fatigue. The intensity is so high that I can’t do it more than twice a month without compromising recovery.
The Role of Hypoxic Training
One caveat: I did much of my limited cardio on an altitude-training system using a LiveO₂ machine, alternating between low and high oxygen environments. High CO₂ levels can dilate blood vessels and improve oxygen delivery, so it likely helped. But I’m convinced the 50-rep single-leg squats were the real driver of my VO₂ max jump. in my opinion, -O2 does not get anywhere near as deep as a 50 rep leg workout.
My Protocol
For the previous six months before test, this would be a typical week.
Monday – 1 set to failure for chest, back, shoulders, arms
Tuesday – Norwegian on Airdyne – 4 min x 3 sets
Wednesday – off
Thursday – Sprints on Airdyne – 2o sec on/1:40 off
Friday – Rest
Saturday – Rest or Leg Day (every 2 weeks)
Sunday – Rest or Leg Day (every 2 weeks)
Single Leg Squat to failure. Aim for 50 reps. Higher reps get further into O2 deficiency. 1 set each leg
Leg Curls or Stiff Leg/Romanian DL. 1 set
Calf Raise. 1 set
Today, I’ve incorporated Tony’s “plyoception” movements 1-2x/week for under 20 minutes.