We are a commune of inquiring, skeptical, politically centrist, capitalist, anglophile, traditionalist New England Yankee humans, humanoids, and animals with many interests beyond and above politics. Each of us has had a high-school education (or GED), but all had ADD so didn't pay attention very well, especially the dogs. Each one of us does "try my best to be just like I am," and none of us enjoys working for others, including for Maggie, from whom we receive neither a nickel nor a dime. Freedom from nags, cranks, government, do-gooders, control-freaks and idiots is all that we ask for.
50% of max heart rate for an hour? It seems inefficient and not stressful enough for my taste (not to mention boring), but maybe as a once-weekly thing on a day following a strenuous weight session it might be warranted as a form of "active recovery." Or, of course, for beginner exercisers, anorectics, the elderly, or the terminally-sedentary.
At the same time, moving at all is probably a better idea than not moving. It burns no fat (not that you need that) and builds no strength, but certainly helps maintain some minimal degree of endurance and mobility.
I tried to introduce one hour of this sort of thing into my weekly regimen a few months ago as a "recovery day" (with a mix of treadmill, stairmaster, and elliptical) but I just can't stay with it. My body seems to insist on bursting into one-minute sprints in the course of it every several minutes, thus converting it to HIIT. Maybe it's because I am in half-decent shape, but my body just wants to pound it every few minutes instead of slogging along. I guess that's a good effect of my fitness training - energy.
I do about 30 to 40 minutes of this six or seven days a week.
It's called "walking the dog". Our standard route is a touch over 2 miles, and includes places where I slip his leash and we play ball.
And yeah, it is good for you. Fresh air, bonding with and training the mutt, a bit of movement. Really, really good. No, it doesn't make you physically fitter, but it might make you "healthier" overall.
On a treadmill? That's really stupid. Go be outside. Being outside is good for you.
Unless you live in NYC. Living in NYC isn't good for you because there's no outside there. Not Real Outside, not for a long distance anyway. This is true of Chicago as well. And probably Boston and Baltimore. Houston and Dallas metro areas...even worse in some ways. LA is just a pit. But I digress.
On the other hand you have to train long to go long.
My max heart rate is 170/172. My RHR is about 58 or 60 (at this altitude. I can feel my heart slow down as I drive down into the lower elevations).
Thing is that general fitness is all well and good, but if you've got goals beyond staying alive and looking athletic, then you question becomes "fitness for what".
That is the real question that everyone has to answer for themselves.
Thing is that half of what you get in the gym is tolerance for discomfort. 3x10 Burpeess won't do you a BIT of on the second day of an off trail backpacking trip in the higher elevations of the Rockies, but the discomfort of doing those burpees will.