“Expert” happens to be the term for the third level of exercise at the fitness course I use. The signs at the stations give three numbers for how many repetitions to do: Beginner, Intermediate, Expert. I do “expert” rep-counts at some of the stations. I haven’t even reached “beginner” on the one where you swing along a horizontal ladder. On most, my rep counts are 51% between “intermediate” and “expert”. My muscle strength and stamina continue to improve. I increase by a rep or two here and there every few weeks. On the way to “Expert”!
Along with rep-counts, the instructions on the sign say whether to walk, jog, or run to the next station. On this question, I am pretty well stuck at intermediate. It isn’t the legs, it’s the breath. I wonder how much aerobic conditioning can improve at an advanced age.