dbacon commented about trying to blow up balloons without letting the cheeks puff out as a way to strengthen them. This reminded me that I've tried this "technique" with a few students to help them get used to or develop the strength required to really blow a lot of air through the horn. I do realize that, idealy, we want to use lots of air that "flows freely" through the instrument, but this is geared toward the times when we're really cranking. What i noticed from the 5-10 kids I've had do this is that those who had much trouble getting any real volume of sound, even though they had consistently good response and, for their age, playing ability, often were UNABLE to blow up balloons! This is a real visual test and indicator of how much air you can move. It's like a home version of the lung capacity machines that measure air output. Just look at the overall size of the balloon on one exhalation (if it expanded at all). Yes, balloon age, size, and shape play a role, so if you try this, use a consistent brand or model.