I remember "huffing anf puffing" for less than a minute during a college physics experiment to measure average human power output. I think I briefly peaked
at just over 2300 Watts [Joules/second] running a staircase; that works out ot
nearly 3 horsepower for this 'old horse'.

Yep! You can, even in a stiff spacesuit, give a 1,000kg [metric ton] payload
in orbit a good healthy push that can send it on its way [even at the end of a tether]
at a relative speed away from you of anywhere upto 1/2 a meter per second, depending on your fitness....If the payload were at the end of a long tether, it would be 1000 meters away in 40 minutes more or less, depending on the mass and stiffness of the tether.

Jacob