I want to know what is the effective weight of doing push-ups. What would be the weight of the dumbbell/ barbell to do a bench press with the same resistance as a push-up. I understand this depends on the person's weight, maybe the answer can be an estimated percentage of the weight?
I asked this question on physics.stackexchange.com for you: https://physics.stackexchange.com/questions/9129/what-is-the-force-on-the-arms-in-a-pushup . The answer is 50% of your body weight assuming equal distribution of mass vertically and weightless arms and head. It will be more than 50% when you factor in arm and head weight and your exact vertical mass distribution. If you're top heavy, you're pushing more weight. If you're bottom heavy, you're pushing less weight.
Roughly 55-80% of bodyweight
Dick Moss has this overview on how much weight we are lifting in push-ups, "citing" an unnamed study:
Studies have been conducted in which push-ups were performed on force plates. They indicated the following:
- Women performing traditional push-ups lift the equivalent of 71% of their body weight. For example, a 120 pound woman lifts about 85 pounds.
- Men performing traditional push-ups lift the equivalent of 77% of their body weight. Thus, a 150 pound man lifts about 115 pounds.
- Modified push-ups, performed with the knees on the ground rather than the feet, reduce the amount of weight lifted. Women lift the equivalent of 55% of their body weight, while men left about 56%. So a 120 pound woman lifts about 66 pounds and a 150 pound man lifts about 84 pounds.
He notes that the difference between the sexes is really just a function of body mass distribution between the upper and lower body:
These percentages are only averages, but there is a reason for the difference between males and females. Men usually lift more of their total body weight during push-ups than women because they tend to have more bulk in their chest and shoulders. As a result, more of their weight lies directly over the arms when performing pushups.
In contrast, women tend to have a lower center of gravity, with their weight centered around the hips and thighs. Since this weight is located below the position of the arms, less force is required to lift from a pushup position.
However, this varies widely, depending upon the individual.
Changes in resistance through the range of motion
It's also important, when trying this at home, to test both the top and the bottom of the push-up position, since the change in angle of course affects how much resistance is applied. Per Suprak, Dawes, and Stephenson 2011:
In both the traditional and modified push-ups, subjects supported less weight in the up vs. the down position.