A question about improving breathing

[Be11adonna]

I am starting week 8 this evening and, as I have mentioned in other posts, am finding it hard going at the moment. What makes it hard for me is my breathing (legs and body seem fine, no injuries, cramps or stiffness).

So this morning, when I discovered Pastyman's post about mouth breathers vs nose breathers, I read it with interest:

healthunlocked.com/couchto5...

My question: does anyone have experience with the PowerBreathe mentioned in the Guardians running blog?

What have you all done to improve breathing/lung capacity etc?