Having a low bone density problem, I was suffering from terrible
back pain.

I heard that push-ups are a great exercise for strengthening bones.
But at the same time, I've also heard that push-ups build muscles!
The more you do, the more muscles will be build up.

Now, I don't want the muscles of Hulk Hogan. It doesn't look nice.

Well, is it true that you'll be building more and more muscles, the
more you do push-ups?
I wish to do push-ups throughout my life but now I am a bit apprehensive.

Besides, I've heard that once we quit this sort of exercise after a
few months, we will become fatter than before?

Maybe running is better for you

push-ups do not build muscles, I mean your hands will not grow in diameter

Don't worry, Ani. I don't think you'll end up like this from a few pushups a day.

I'll be serious for a moment. Calcium deficiency. Get some multivitamin and mineral tablets.

Well, not according to Wikipedia (this also matches what I remember learning in high school gym class):
Therefore the more push-ups you (can) do, the less effect they'll have on your muscle size.

I guess if you do a significant amount of exercise you might start eating more. Then if you stop exercising but don't eat less...

For years, I was working out, doing pushups and many other exercises until a trainer pointed out to me that the rate of my workout, while improving strength, was also causing my muscles to atrophy because I was running out of energy the muscles needed. That made sense at last because all that time and I built up so little muscle, good tone, but not much mass. So, it depends on how you're working out.

Back pain- dont do many, if any, pushups. They are NOT good if you've got back problems.

*edit- low impact, low back loading exercises are what you want to do to help with back pain- cycling and swimming are the best IMO.

Yoga and/or pilates would probably help as well.

You wont, unless you do hours of training every day. Even if your were male, you'd probably also need some steroids to look like Hulk Hogan-

http://www.youtube.com/watch?v=OUrNrB8jl84

Sort of. I dont 100% agree with ntubskis wiki info, here is my version-

High weight, low repetitions- builds 'bulky' muscle. (eg lifting 50KG x 5)
Low weight, high repetitions- builds 'dense' muscle. (eg lifting 5KG x 50)

Both will increase your overall strength, and will have some effect of your muscle.....even if you do huge numbers of repetitions with very low weight.

But you dont want bulky muscle, you want dense muscle. IMO even guys look a bit silly when they are overly bulked, and it doesnt look good on women. Its possible for women to have dense muscle, be quite strong and very fit, and look great. Since women have much low testosterone levels, that outcome is almost 'standard', to get bulky requires a more targeted approach (specific exercises, sets, tempos and probably steroids in most cases)

Even some of the professional female fighters (eg MMA) are not huge women with muscles like an a̶c̶t̶o̶r̶ ....err....'wrestler'. Eg, Gina Carano-

http://en.wikipedia.org/wiki/Gina_Carano

Again, sort of.

Do more exercise, and you'll need more food. Well, unless you're living in a western country (particularly the english speaking bits of the western world) and eat the 'average diet', then you wouldnt need any more food.

Get used to eating more, then when you stop exercising your appetite is still the same as it was when you were doing the exercise.

Similar calorie intake + lower exercise = weight gain.

Women don't become muscle-bound hulks from eating normally and doing regular exercise. They just end up looking... better! The same is largely true for men too.

You shouldn't have said that, they'll rip you to shreds very soon. Those multivits are dangerous things, can kill a man real quick. You gave poor Anisha a death sentence. RIP Anisha...

Exactly. (Except for women with abnormally high testosterone levels.)

Pushups are fine. Review some videos online (on credible sites) that demonstrate proper form, and/or have a knowledgeable friend observe while you're doing them.

Planks may be a better starting point for now, though. Build up your core strength so that you're starting with a stable foundation. (Same thing, see online vids for proper form.)

If your back pain worsens, see a doc...

Er, Any muscle, used repeatedly, will get bigger. Its kind of a biological thing. As long as you are eating enough calories including a reasonable amount of protein, you will get stronger and build muscle.

Push ups will only work one set of muscles, you need to do a range or different exercises to utilise all of your muscles.

Swimming is a very good place to start. Its low impact on joints unlike running, it works your whole body, it builds cardio vascular fitness as well as muscle, and if you are currently suffering from back pain it allows exercise while supporting your body weight.

You need to be careful to only do as much as YOU can currently manage, you want to exercise, NOT hurt yourself. The vast majority of people who have to stop comming to the gym do so because they have overdone it.

Why are you asking the LQ community a question better answered by health and fitness experts? If you actually trust your LQ friends the most, that's great, but posing the question here is still like asking experts on muscles about a Linux problem.

newbiesforever has a point. I mean:

What did we say about taking medical advice from a Linux forum?

Ah, yes, I remember that thread.