At 65 my wife and I go to gym on a MWF schedule. We need a day in between and the weekend to recover.Still following a 3 day a week schedule Sunday, Tuesday, Thursday, then 2 days off. Have been doing this for about 35 years now. HRM's hate them, use them, most of the time I use the one on my BPM. Never went to using heavy weight lots of reps for toning, saved some aches and pains.
At 75 with that schedule you have my respect.