You lose muscle mass as you age but perhaps more important you lose bone density and bone strength. If you regularly stress your bones, they are stronger. Runners have great bone density but bicyclists have terrible bone density.

I know several people my age that fell and cracked a pelvis or hip or broke an arm, simply from a fall. If they were 20 years younger, I am sure they would not have broken anything.

In winter when I am not regularly cycling outside, I try to go to the gym three times a week. Do about 25 minutes of strength exercises and stretching exercises. Some of these were ones that I thought made sense or a trainer had told me to do years ago, some at the suggestion of a physical therapist. Then 60 minutes on a bike or stairmaster. I also do backpacking in the summer, so when I do a stairmaster I wear hiking boots with ankle weights.

The strength exercises, I am setting the weights on the machines so it is REALLY hard to push. That is to stress my bones. I am sure it helps for muscle mass too, but the main reason I am doing those exercises is for bone strength, not for muscle mass. That is why I set the weights so high, I want the bones to be stressed. For leg strength I do the leg press. I do the most weights that I can actually do. About every month or so, I will add another weight, if I can't push it, then back down. I had a bone density test a couple years ago, result was classed as normal.

During summer when I am biking outside, I drop to one trip a week to the gym, I steadily lose strength during the summer because I am not going as often, slowly have to reduce how many weights I can lift. Then in fall, start building muscle mass and bone stress all over again.

I should note that I am retired, if I was not it would be tough to find the time to do this. It is almost like a part time job.