Do you know any singing breathing exercises?

Question:

Do you know any singing breathing exercises?

I know proper breathing but I still feel short of breath. You breath in until the abdomen is expanded then let the air out slowly in one continuos motion. Even if I lay on my back I can't hold a note for more then 4 seconds without falling flat. I know I am running short of breath when I begin to go flat. If I use my head voice or deep chest voice I can hold the note really long but not in my middle register. I had my first lesson where the teacher won't me to be able to blow a 12" baloon in one breath. I would ask her for exercises, but she is on a two week vacation. Do you know any exercises that will increase how much air I can hold?

Best Answer - Chosen by Asker: Here are two different techniques. First: go swimming - a lot! Stay under water for as long as possible

Second: Breathe in through your mouth for 8 counts making sure you fill your lungs in that time. Breathe out for 8 making sure you completely empty your lungs in that time. Alter the time by going up to 24 counts and working back down to 4 counts and then 1 count. This will teach you how to use the air that you are given. You will be surprised at how long you can hold a note with one quick breath!

Here is a count breakdown for you to work with:
8
16
24
16
8
4
1

It's very important to make sure that you are completely filling your lungs with the time given and then completely emptying them within the same amount of time. Use a stopwatch to ensure that your measurement of times are equal.

To further strengthen your lungs slow the counts down.