The phrase
"chest breathers" refers to individuals who primarily breathe using their chest muscles instead of their diaphragm, which is the preferred and more efficient way of breathing.
Full definition
If you're a
habitual chest breather, it can take a ton of practice to make diaphragmatic breathing your new default breathing pattern.
They're
chest breathers, and they're not breathing into their abdomens.
Too many people are
chest breathers, meaning they rely too much on chest, rib and neck breathing muscles relative to the diaphragm.
If you're not a trained singer, a swimmer or haven't practice Yoga breathing techniques, you probably are
a chest breather.
Well that's an article in itself, but lets just say if you are
a chest breather, you are likely using muscles designed to lift the shoulder and lower the rib cage.