I just did 20 minutes of vigorous aerobic exercise per day for 8 weeks.

It was pretty good, I guess. My fitness is much improved. 150 minutes per week is what all the public health information websites recommend that everyone should get, so according to them I'm almost doing the bare minimum for the first time in my life. I'm pretty old, so it took some time for it to start having an effect. It feels like it will probably take another 8 weeks before my body actually starts getting used to it and stops getting stronger so quickly as it still is doing for now.