When doing a push-up, what percentage of your body weight are you lifting? (I.e., how much would you be bench-pressing if you were on you back and lifting weights, instead of on your belly, lifting your self?)
It’s right around 2/3 of your bodyweight. It’s really easy to figure out–weigh yourself, and then do a pushup with your hands on the scale.
This sounds about right, OTOH although I can comfortably crank out 50 pushups, I’m not sure I could do 50 reps at 110 pounds - I weigh 165.
It may be that the “weight” varies more throughout the arc of the pushup, offering a greater degree of rest than a bench press. Also pushups bring in the abs more.
I’m going to try this out later in the interests of science.
It’s not only the weight, but how you lift it.
…and that’s all I can manage after 3 hours of sleep.
I’m pretty sure you hit it on the head with the arc issue. You would be lifting the most weight at the bottom of the pushup when your body is pretty much parallel to the ground. At the top of the pushup, the energy you exert goes partially to lifting your body vertically and partially to moving your body horizonatlly(which really does take that much work).
I did a quick back of the napkin calculation. For my height and weight (assuming that the 2/3 weight is at the bottom of the pushup), I would be lifting 147 lbs at the bottom of the pushup and 136 lbs at the top. For 110 lbs, you would be lifting 102 lbs at the top of the pushup. Of course, that is using my calculations for height and arm length, but it is reasonable to assume that the ratio of arm length to height would be pretty close for most people.
Even if a scale shows 2/3rds (I haven’t tested that claim) a push up is much more leveraged overall. At best you’re lifting (IMO) 1/2 the amount in comparable bench press exercise, and probably less.
I tested the 2/3 notion, and only made it to 35 reps bench pressing 110 pounds (I weigh 165). i’ve never tried to do pushups until collapse, but can do 50 without too much sweat.
This seems to confirm Astro’s position.
I’ve also noted that on bench press machines with fixed plates I lift about 50% more weight than with a free barbell. This is presumably due to leverage.
And because if you’re using a machine you don’t have to worry about making sure the weights don’t wobble, which takes a lot more energy than you think, even when you’ve done it.