Are you breathing properly?
It sounds strange to say it, but generally we don’t breathe optimally. Years of poor posture, anxious thinking, tension and press result in less than ideal breathing techniques. We tend to breathe through our chest and we suck in our stomachs when we breathe in. What we really need to be doing is breathing through our diaphragm (watch a baby - they do it correctly), which is more healthy and more natural. Breathing correctly, our muscles move downwards creating a vacuum drawing air into our lower lungs, which then causes a slight expansion of our abs and ribs (not sucking our abs in!). The chest expands and our upper lungs fill with air.
Firstly see how you breathe - have a hand on your chest and the other on your stomach. Breathe normally and see which inflates first when you breathe in. If it’s your chest then try breathing in through your stomach and exhaling and drawing your tummy button to your spine, while drawing on your pelvic floor (it will also draw on your transverse abdominus, which is part of your core).
It takes a bit of practice! Let me know how you get on.
Not sure what you’re doing? I can direct you to some good videos so let me know