In addition to the above advice, here are a couple of additional reasons that a specific heart rate target might not be an effective measure for what you’re trying to accomplish.
Heart rate varies dramatically from person to person. And a person who is cardiovascularly fit might have a quick recovery heart rate (HR comes down fast to whatever number you name), but not be muscularly ready to do another set of the same muscle. So I wouldn’t pin any activity on a specific number.
That said, you got a good suggestion from Natalie regarding circuit training. If you are training one person, you can plan a circuit that doesn’t involve a lot of stations so there’s not a lot of transition time. I like to design circuits that cycle through push / pull / leg / core, all using the same equipment (usually a CrossCore or a ViPR) or the same location on the training floor so there is very little rest.
With that skeleton of push, pull, leg, core, I can keep the workout very fluid, changing and progressing the exercise as I return to it for the next set.
set 1, push – CrossCore push-ups, bilateral
set 1, pull – CrossCore rows, bilateral
set 1, leg – Med ball squat
set 1, core – med ball lateral flexion in wide squat (plie)
set 2, push – CrossCore push-ups, unilateral, no torso rotation
set 2, pull – CrossCore rows, unilateral, no torso rotation
set 2, leg – Med ball squat, change the tempo of the squat
set 2, core – med ball rotation, low to high left to right
set 3, push – CrossCore push-ups, unilateral, transverse torso rotation
set 3, pull – CrossCore rows, unilateral, transverse rotation of torso
set 3, leg – Med ball squat, bodyweight shifted to 75% on one leg, 4 right, shift to other side, 4 left, shift, 4 right, shift, 4 left
set 3, core, med ball rotation, low to high right to left