From 41 to 50 ml/kg/min: Why 4-Minute Intervals Beat 20-Second Sprints for VO2 Max After 40

What I Discovered While Plateaued at 41 ml/kg/min

After months of aggressive REHIT protocols on my CAROL bike, I hit a wall.

My VO2 max plateaued around 41 ml/kg/min despite consistent training, mycotoxin detox protocols, and comprehensive supplementation.

The CAROL was delivering results for neuromuscular adaptations—my grip strength jumped from the 27th to 87th percentile—but my cardiorespiratory system refused to budge after an initial increase from 36 to 41 (already excellent).

That’s when I discovered the Norwegian 4×4 protocol, and it fundamentally changed my understanding of what drives VO2 max improvements in already-trained athletes. I have now integrated this protocol with my Carol + cardio current protocol.

I am also even more motivated because the impact of this protocol on longevity markers has been proven beyond any doubt.

Longevity Markers

Telomere Length: Sustained high-intensity exercise activates telomerase, potentially slowing telomere attrition.

Inflammatory Regulation: Regular 4×4 sessions reduce chronic inflammation (lower IL-6, TNF-α) while improving acute inflammatory responses.

Cognitive Function: The protocol improves cerebral blood flow and BDNF production, enhancing neuroplasticity and cognitive performance.

In this article I share how it works and how you can integrate it in your own fitness plan to dramatically improve your VO2Max.