A specific interval training protocol (1.6 miles at 4% grade, 4-minute repeats, 6-minute recovery, 4 reps, twice weekly for 3 weeks) can significantly increase VO2 max.

“there was a workout I would do you know in Carmel Valley you've got the 56 that goes out and it's got a bike path next to it there's a section of that bike path that is 1.6 miles long and it goes up at about 4% and just doing repeat intervals of that which takes about four minutes all out to go one direction and then about six minutes to cruise back four of those that was it twice a week for like three weeks and your vo2 max exploded”

“do you think that once a week doing those four hard intervals is sufficient to boost V2 Max it will increase it for sure yeah in the vast majority of people especially if they're doing the other stuff you're talking about”

“24 sessions of high-intensity interval training over eight weeks improved VO2 max by 12% in healthy individuals.”

“one minute being sort of like probably the the bare like the minimal effective dose for improving V2 Max like at least getting in one doing some one minute intervals and repeating that four or five times”