It would vary depending on type of exercise. Giving my opinions based on being very interested in the subject for years, without bothering with citations. For

It would vary depending on type of exercise. Giving my opinions based on being very interested in the subject for years, without bothering with citations. For muscle-mass, the health benefits come from having higher glycogen storage (helping to prevent diabetes), as well as maintaining function late into life. The latter is subject to diminishing returns, and maintenance is more important than the amount when you peaked. Also, having too much muscle mass would put a strain on the heart. Daily light movement is important for circulation. 10-12k steps seems to about ideal. 15-20 minutes of moderate-intensity (120-140 bpm) or 4 total minutes of high-intensity (> 160 bpm) cardio improves heart function, blood-flow, and mitochondrial density. Any more seems to be subject to diminishing returns. Stretching around 10 minutes per day may help prevent cancer and preserve function. This leads me to the following recommendations: 1-3 weekly strength training sessions of around 45 minutes 10-12k daily steps 2-4 weekly cardio sessions of around 15 minutes 10 minutes daily stretching