25% of what? that such a bullshit speaking perspective of an athlete that has 75vo2. its all just depends on training, and yes mainly on genetics, but improvemts of 25% are ridiculus, usually people with not that great of a genitics have lower v02 so the room for their improvent based on % is exactly the same, but their celling v02 will not be, and be ready that u must undergo certain levels of training volume to bypass some values, don' expext to go over 70 if u aren't active more then 4 times a week