Kinetic Analysis of the Push-Up: Which Version Is Hardest?
It's a thought that comes up often during workouts – just how much weight are you moving while performing a push-up? And what is the difference in load between a knee push-up and a toe push-up? Or what about an elevated push-up?
Recently researchers at a handful of universities in Michigan, Wisconsin and Pennsylvania endeavored to answer this question. The goal of their study, Kinetic Analysis of Several Variation of Push-Ups, was to create a hierarchy of push-ups based on the training load of each variation. Previous studies had examined the differences in load caused by varying hand placements, but no one had ever examined the effects of feet or hand elevation.
Also noted in the study were subjects body mass, gender, and height. Researchers were curious to see if there was a difference in load based on gender or on height differences. 23 individuals termed “recreationally fit” were observed by researchers and performed six variations of the push-up:
- Regular push-ups
- Flexed knee push-ups
- Feet elevated on 30.48 cm box
- Feet elevated on 60.96 cm box
- Hands elevated on 30.48 cm box
- Hands elevated on 60.96 cm box
The width of the pushups was the width equal to the distance between the individual’s acromion processes. Width was measured from the inside border of each hand with hands placed under the shoulders with elbows fully extended.
Two repetitions of each push-up were performed during the testing phase with one minute of rest in between each variation of push-up. Push-ups were performed at a speed of two counts in the eccentric and two counts in the concentric phase, i.e. two counts down and two counts up.
The ground reaction force (GRF) for each set of push-ups was measured. GRF is the force exerted by the ground against the body in contact with it. GRF is equal and opposite to the force the body is exerting against the ground.
From the measurements, researchers were able to determine load as percentage of bodyweight for each type of push-up:
- Feet elevated on 60.96 cm box – 74%
- Feet elevated on 30.48 cm box – 70%
- Regular push-ups – 64%
- Hands elevated on 30.48 cm box – 55%
- Flexed knee push-ups – 49%
- Hands elevated on 60.96 cm box – 41%
Researchers determined kinetic characteristics did not vary between genders nor did subject height did have a correlation with GRF, except for when the hands were elevated to 60.96cm.
It is the hope of the researchers the information gathered in this study will help trainers order push-up progression from lower to higher intensity for their clientele. In addition it should help them relate the push-up to resistance movements by knowing the approximate load as a percentage of body mass. This would enable trainers to determine similar loads using free weights or other means of resistance training.