Earlier quoted context omitted.
Well, it's causing muscle contractions. At high enough intensity, it should raise your heart rate. It's just a matter of what intensity level is tolerable during sleep (and the effect on sleep quality), no?
No, that would wake you up long before it had cardiovascular benefit. You need your heart rate up into zone 2 to 5 to really have a positive impact. That's 120 BPM plus for most people. Once you're around 80 it'll wake up anyone, even someone with very low cardiovascular fitness.
Source? I haven't been able to find info on this. I get resuls on nocturnal tachycardia and such. Nothing on elevating a sleeping person's heart rate and observing the result, though.