Stretching the diapharam is the way to fix it.

So generally holding your breath works well if done properly

1) Inhale as much as you can in the normal method

2) Take a mouthfull of air and force it into your lungs.. do this a few times until your lungs feel like they are ready to burst

3) Stretch. Roll your shoulders. Point your arms up and bend back and forwards. Stick your chest out etc

Works for me 90% of the time