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I was at a coaching clinic recently watching the boys do regular pushups with their feet on the ground, and the girls were doing knee-pushups with their knee on the ground.
Moreover, sometimes I raise my feet on a chair to add extra “weight” or resistance.
How much weight do you actually exert with push-ups? How much LESS are knee-pushups? How much MORE is it raising your feet? Since everyone’s height, arm length, and weight distribution differs, the actual percentage of your weight that you lift during a pushup will vary.
So I asked our resident expert in physics, University lecturer Dr. Spathopoulos, to write an article about it.
This article is guest blogged by University lecturer Dr. Vassilios McInnes Spathopoulos, author of An Introduction to the Physics of Sports
. You can read my review in Introduction to the Physics of Sports.
He also wrote Windy Records in Track & Field and The Effect of Wind on Curve Running. To read all his articles on this Blog, click here.
How much weight do you lift with push-ups?
Push-ups are one of the most widely used exercises for developing muscle power and endurance. The biomechanical process involved is relatively complex and its analysis would be beyond the scope of this short article. A few studies have been performed in recent years (for example, refs [1] and [2]) and it can be shown that the principal muscles deployed are the pectoralis major and the triceps branchii. So how much weight to these muscles actually support when performing the exercise?
A literature search can reveal the following: The supported weight is limited by the bodyweight of the individual and is usually expressed as a percentage of that bodyweight. A larger weight is supported in the “down” position than in the “up” position. Finally, variations of the standard dynamic push-up, such as the knee position or the elevated feet position can significantly reduce or increase the supported weight.
Exact figures vary from study to study and will obviously depend on the exact anthropometric features of the participants. It is possible though to deduce some ballpark estimates that could be useful for coaches and athletes. We can say that the peak force experienced will be equivalent to lifting about 65% of your bodyweight. Reverting to the knee position would reduce this by about 15%. Finally, the increase caused by lifting the feet on a chair will depend on the exact elevation height. Lifting the feet by about 60cm will result in a force increase of about 10% with respect to the standard position. So in summary, an 80kg individual will be supporting about 52kg in the standard position, 40kg in the knee position and 60kg with the feet elevated to a height of about 60cm.
Once again it should be stressed that the above figures are approximate. Nevertheless they do demonstrate the important fact that the push-up exercise can be modified in order to suit the needs of each individual. Next time you are stretching those muscles, remember how much weight you are actually lifting!
[1] Gouvali, M. K., & Boudolos, K. Dynamic and electromygraphical analysis in variants of push-up exercise. Journal of Strength and Conditioning Research, 19, 146-151, 2005.
[2] Ebben, P, W, Wurm, B, VanderZanden, L, T, Spadavecchia, L, M, Durocher, J, J, Bickham, T, C, and Petushek, J, E, Kinetic analysis of several variations of push-ups. Journal of Strength and Conditioning Research 25(10), 2891-2894, 2011.
About the Author
Dr. Vassilios McInnes Spathopoulos graduated from the University of Glasgow (UK), with a joint honours degree in Aerospace and Electronic Engineering, in 1995. The following year he completed a MSc course in Flight Dynamics at Cranfield University (UK). In 2001 he obtained his PhD from the University of Glasgow, conducting research on the validation of a rotorcraft mathematical model by means of flight testing a gyroplane. He teaches undergraduate subjects at the Department of Aircraft Technology, at the Technological Education Institute (TEI) of Chalkis, Greece. His research interests include the aerodynamics of sports balls and improving engineering education.
So in summary, reverting to the knee position would reduce the force by about 15%. Lifting the feet by about 60cm will result in a force increase of about 10%.
Vassilios McInnes Spathopoulos
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The formula works great. I tried it at home with a single scale and got almost exactly 65% of my bodyweight like the article said. I weigh 210 and I got about 135 on the scale in the “up” position