I practice on average an hour and a half every day, some times more, sometimes less but since I started practicing for this amount of time (4months), my back starts to hurt really badly after the first hour. Does anyone else have this problem or is it just me?

I had that problem last semester.

The doctors preliminary diagnosed it as thoracic outlet syndrome.

Do you by chance have scoliosis?

If your back starts to hurt after an hour of practicing, then you should only practice for an hour at a time. Personally, I find it's more efficient to have several shorter (and higher energy) practice sessions throughout the day, rather than one long practice that's more a test of endurance than anything else. Then, there are the really insane people that go to the practice rooms several times a day for several hours at a time...

If something starts hurting when you practice, you should stop immediately. Continuing to exacerbate the problem can lead to serious injuries down the road, and sometimes these can prevent you from playing for good.

I suggest you have your playing position checked by a good teacher or experienced player. It may be that yours is not correct and you are straining your back muscles or column too much. This can be serious if not corrected and just practising less is no solution at all, IMO.

are you holding (gripping the flute) or balancing it? practice in front of a mirror, and like previous advice,work with a competent teacher

It is not unusual for experienced players and professional to study several hours a day, without any harm to hands, neck or back. I would not call this practise "insane", being in fact very common and moreover, important and necessary in most cases.

The main issue is to have correct a technique, including body and arms position, the pressure of the fingers and so many other factors.

I had problems recently with my left hand, due to incorrect technique and I an correcting a few things, I hope it is not too late.

By "insane," I am referring to someone I know that has been known to practice for four hours, eat dinner, and then go practice for five more. It works for him, but if anyone tried this and they were not completely relaxed and balanced for the entire time they set up camp in the practice room, they would get a RSI pretty quickly with practice habits like that.

Practicing several hours a day is a necessity, but you don't have to do it all at once. Depending on how you practice, it might not even be healthy to gut it out for more than an hour at once. I put a lot of energy into my practice sessions, and after an hour I get tired and I find that it only fosters bad habits that can negatively affect my playing, and could even cause injury if I forced myself to keep practicing longer. Practice for as long as is efficient and pain-free, then do your homework for a while. After you get sick of that, you can go back to practicing feeling relaxed and rejuvenated. If you start early in the day, 3+ hours adds up pretty easily, and it's more productive and pain-free than if you did it all in one go.

I agree. I noticed that the more you advance in the study, the longer you must study to keep the level and advance further.

One should not get obsessed with this, however. At may present level and my personal conditions, I believe it require not less that one and a half hour daily and it should be at least two hours if one add the long notes exercises, the scales and other technique homework.

Nine hours a day seems to be too much indeed. But I am sure that one is not the only case here.

I am temped to open a thread with the question: "What is your perceived performing level presently and how many hours you practise per day (or per week)?

But I will just float the idea, I'm not in the mood of opening new general threads for the moment..