Sorry, took longer to edit than allowed. Let me explain further. (Graphs taken from Attia.)
The second graph (above) shows how VO2 declines with age for people of high (95% for age), average (50% for age) and low (5% for age) levels of fitness, as well as the VO2 needed to do various strenuous activities. Taken from Attia, the data is from a 2020 book by Ligouri from the ACSM.
The first table shows VO2 ranges (and METabolic eqivalentS which are multiples of 1=“at rest”) for men and women by age range and fitness of low (bottom 25%), below average (26-50%), above average (51-75%), high (75-97.6%) and elite (top 2.3%). The data is taken from the JAMA study below. Essentially, an eighty year old man in the top 2.3% of fitness has the same VO2 max as an unfit nineteen year old woman (in the bottom 25%). Basically, comparing a 60 year old man of fitness X% for age sixty, an eighty year old man would be roughly the same as fitness (X-25)% for age sixty (and X>25).
To reduce the drop in VO2 max which occurs with age, you want to do strenuous activities, particularly ones lasting longer than a minute. VO2 testing often uses activities from 3-8 minutes at a high (but not maximum) level of intensity, say a “perceived exertion” of 8/10 or so.