What Kamandi said regarding situps.
Regarding pushups: These require a lot of upper body strength, which tends to be a weak spot for women. Once you have the ability to do pushups, they’re a great way to develop upper body strength — but, as you’ve noted, you’ve got to work up to that level. Let me suggest a way to build up to that:
Start with wall pushups. Stand next to the wall, and do your pushup into and away from the wall instead of up off the floor. This way, your body weight is fully supported by your feet, so you have a lot less weight to push up and away from the wall. You should be able to do a lot of repetitions this way. When you feel like you’re not challenged enough, or it feels as if you’re doing way too many repetitions, it’s time to up your level of difficulty.
To make this more difficult, step back further from the wall. To make it more difficult still, stand on one leg, with the other one lifted or crossed behind the first one. Again, the further back you stand for the wall, the more difficulty you’re giving to your upper body. Once these get pretty easy, you’re ready to graduate to floor pushups — first starting with pushups from your knees, and possibly later on to full body pushups with your weight on your toes.
The wall push up part will let you build up your arm strength. The other difficult part of pushups is having the trunk strength to maintain good form during your pushup. You should have a straight line between your shoulders and your knees (or your feet, if you’re doing a full pushup.) A lot of people tend to push their fannies up in the air when they’re doing pushups, which is a method of cheating.
One way to develop the trunk strength needed in pushups is to do a plank maneuver. To do this, lie down on the floor face down. Put your arms beside you, with your elbows close in to your side, and your palms down on the ground. Lift your body up off the ground, with your weight resting on your forearms and your knees (or, when you’re more advanced, you can go to your weight resting on your forearms and toes, as in a full body pushup.) Once you’re up there, hold. Start with 15 seconds or so if you can, then rest and repeat. When you can maintain the proper form on this, hold it for longer intervals.
This sounds simple, but it is intense. And remember, it’s called the plank for a good reason. You want to keep your body as straight as a plank. If you start sticking your fanny up in the air, you’re cheating.
I notice that I typically end up with my hands making sort of a triangle shape, nearly meeting under my face when I do this. You can do the triangle, or keep them straight if you prefer.
So, here are some options to work up to pushups. It may start out slowly, but it just takes some time and effort. Keep in mind that you’re going to get a lot more out of doing 5-10 pushups with excellent form than 20 fast pushups with your fanny up in the air, pumping them out quickly so that you rely on momentum (which is the way I see LOTS of people doing them.)
Note: Upon preview, I noted that I used the term “fanny” in several spots. I’ve learned recently that those of you in the UK have a different reading for that term than I’m used to. In my parts, “fanny” is the kinder, gentler term for buttock, rear end, derriere, gluteus maximus, etc. No offense is meant…