# The Maths of Exercise

Lets say for whatever reason You can't do a pushup to save your life. You can't manage the technique and it hurts you too much. Or lets say you're like me and can't do a sit up to save your life because your legs end up pulling you up rather than your core muscles. Now lets assume you're in average shape (Not too lean, not too round) and for easy calculations sake that your body in total weighs 100 kilo. (The reason for 100 is that everyone can easily work out a percentage and apply it to their own weight once the answers flood in)

With those parameters in mind, which piece of equipment(s) at a Gym and with how much weight would equate to a push up, a sit up and a pull up?

The reasons for this question is like I say, I struggle with sit ups. I'm getting better at pushups and I'm just able to endure three pull-ups without crying afterwords. But situps are something I just can't do. However, there is a machine at my gym that I think will equate to a sit up if I apply enough weight to it. Rather than asking for myself I figured I may as well generalise the question so more readers can benefit form the answers.

• An example of an answer I'd like is say: The weight exerted on a 100k person's muscles during a sit up would be X kilo and the machine to target them is X, X or X. Feb 17, 2019 at 23:44
• Related to this question. What you actually are asking is "How can I scale sit-ups, push-ups and pull-ups, if I can not complete one repetition of those exercises?". Consider a title like this, splitting this question into one question for each exercise, and doing searches like this one Feb 18, 2019 at 8:22
• "can't do a sit up to save your life because your legs end up pulling you up rather than your core muscles" - This is because a situp is a hip flexor exercise, and not a core exercise. If you bend at the hip, you use your hip flexors. Your abs are used to bend at the torso, for which you would do crunches instead of situps.
– Alec
Feb 18, 2019 at 9:24
• @Alec abs still work isometrically in sit-ups. Feb 19, 2019 at 0:23
• @DavidScarlett - Hehe, good point. You also work glutes isometrically in a proper bench press. My point, though poorly worded, was that there are better options for abs than a sit-up.
– Alec
Feb 19, 2019 at 8:37