Functionally, is doing a push up equivalent to doing a body weight bench press?
If not, how does it differ? If I don't own a bench press, can I adapt push ups... E.g incline... As a substitute?
Functionally, is doing a push up equivalent to doing a body weight bench press?
If not, how does it differ? If I don't own a bench press, can I adapt push ups... E.g incline... As a substitute?
Functionally, is doing a push up equivalent to doing a body weight bench press?
Functionally close enough as a movement to where pushups can be a reasonable alternative for beginners. But a bodyweight pushup is nowhere near the same feat of strength as doing a bodyweight bench press.
When you do a pushup, consider how far each body part travels.
your shoulders will gain an elevation roughly equal to the length of your arms
your pelvis doesn't really travel very far off the ground
Your knees even less so
your feet gain no elevation at all
All this means that you're not actually pressing with a force that equals that of lifting a bar loaded with whatever you weigh, because when you do a bench press, the entire weight travels the entire range of motion.
As a point of reference, get in the pushup position, but with your hands planted on a bathroom scale, and see how much you "weigh" in that position, compared to standing on it with your full body.
I don't own a bench press, can I adapt push ups... E.g incline... As a substitute?
Yes and no.
Yes; you will train a lot of the same muscle groups, and there are so many cool variations on the pushup you can do to make sure you consistently challenge the muscles in question. Moreover, there are ways to add weight on top of the variations.
No; anyone who has trained in the gym for years, utilizing the bench press as the primary movement for building raw strength particularly in the chest area, will find it hard to produce the same progressive overload in terms of weight if they can't have the bench any more. They can definitely find pushup variations that are brutally challenging, but in terms of the weight you can load onto a bar, replicating that in the form of a pushup is almost hopeless. But making sure to do it anyway is the best way to maintain as much strength as possible until they can access a bench again.
The good news is that for 99% of us, there are pushup variations and combinations that will serve all our needs. I'm not going to start listing them because there are frankly so many, I wouldn't know where to start. And also because while there exists hundreds of variations, there also exists thousands of lists.
When it comes to the muscle groups involved in actually lifting your face off the ground, a regular push-up and a bench press are identical.
Spacing your hands differently and/or rotating your hands for a press-up will engage different muscle groups. These can also be done with a bench press to some extent. It is somewhat less convenient - positioning your hands closer together gives you less control over the weight, and you'd need a different bar to rotate your hands - but it is achievable. Some machines have different grips to let you do this.
The primary difference though is that a push-up requires the body to be held in a straight "plank" position. This is an isometric workout for your core, in the same way as a regular plank. A bench press fundamentally does not require your core to be engaged in the same way, only insofar as is required to stabilise driving the weight upwards, so a push-up gives you additional exercise which a bench press does not.
If you want the equivalent of a light bench-press and many reps, you can drop to your knees instead. This also reduces the core workout, if this is an issue. Alternatively you can place your hands on a higher surface such as a chair, requiring less load on your arms.
If you want to increase the difficulty, you naturally go the other way. Placing your feet on the chair instead will put more load on your arms, making the exercise harder.
There is a natural limit to this though. If your feet are higher than your arm length, you'll start to work your shoulders instead of your pecs (as with a pike push-up - see later). If you reach a point where your own bodyweight is still insufficient with elevated-feet push-ups, you can increase the difficulty by placing weights on your shoulders. You can use a small rucksack for this, and the weights can be anything (bottles of water, sandbags, whatever), but do ensure any weight is securely between your shoulderblades. You don't want the weights to fall to the bottom of the rucksack and then be pushing on the base of your back, or slip the other way and push on your neck. If you work out with a friend, they can simply place a foot between your shoulderblades to make this harder. Or if you have kids, get them to sit on you. :)
To increase the difficulty, you can also move to a one-arm push-up. This requires significantly more core strength, since there is an asymmetric load on your upper body, but if you're looking for more difficulty then that's no bad thing.
This only considers the "normal" push-up. Variations exist which develop other/additional muscle groups. For a few examples:
The "knuckle" push-ups beloved of martial arts not only toughen your knuckles but also give an isometric workout for your wrists, preventing the standard boxer's injury where they break their own wrist by punching someone. This can be reasonably well emulated by pressing two hand weights instead of a bar.
Pike push-ups work your shoulders more than your pecs. These exercise different muscle groups - the equivalent would be a shoulder press, not a bench press.
Plyo push-ups use the same muscle groups, but are aimed at fast-twitch explosive responses. These are harder to do with free weights, because of the problem of keeping the weight stable; and even with a machine it's likely to cause crashing weights which is not recommended.
Many other variations exist, of course.
Here is a diagram of a person in the bottom position of the push-up:
Let us call his length L and his mass m. We place an origo in the foot. Let us assume that his Center Of Mass is located at x=1/2L and that his shoulders are at x=3/4L. His mass creates a clockwise torque trough the foot: M1=1/2Lmg, where g is gravity of earth.
In order to lift himself up he must create a counter clockwise torque by pushing with his arms: M2=3/4LF that is at least as large as M1. Let us set M1=M2: F = 4/(2*3) mg = 2/3 mg So in other words he must push with a force equal to 2/3 = 67 % of his bodyweight.
Now to the question if you can do push-ups instead of benchpress: YES! Push-ups is a great exercise that trains the same muscles as the bench press + trains the abs isometrically.