I disagree. I ride my geared hub motor unpowered most of the time. Geared hub motors don't drag unpowered. I can get my heart rate up to 168 on steep hills when I run out of breath. If the wind is >13 mph in my face, I don't ride at 4 mph for 6 hours, I turn the motor on. 3 1/2 hour trip whatever the wind is doing. If my knee locks up (I'm an Army Vet from the seventies/eighties, no cartlege in knees) I turn the motor on all the way home. Electricity allows me to control my exercise, without calling a tow truck on the bad days.
PAS is useless. Mine was too fast level one, accelerated too fast, whacked me in the back of the leg when I tried to start. I use the throttle. I deleted the PAS pickup.
You have to ride a lot farther with a mid-drive, or a lot faster, to get the same exercise. My heart runs 120-140 bpm typically at 8-9 mph, which doesn't hurt as much as 20 if I get knocked off. I only broke a bone once, and that was at 25 mph down into a viaduct with loose gravel that caused a skid.
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to save your knees you want to spin. you usually have a far better cassette on a mid drive. the drag is not a issue and the heavy rear wheel will cause more issues. you can get any amount of workout on a mid drive but you can do it faster. like I would get about 200 watts at 15mph with no assist 18 or so on the lowest level 22 mph on tour 24 or so on sport and 26 on turbo all the time putting out the same amount of watts from my legs. I can spin up hills and down and on flats like a road bike. with a bike its better to spin and go longer distances then harder for shorter distances thats hard on your knees. when you can go 50 miles and burn 1500 calories your doing pretty well. going 8 to 9mph would make me fall asleep (G) on group rides thats about where I sit and I am lucky to get my heart rate up to 100
