Hi, I have seen these recently and wondered if anyone had any experience of these and if so, are they worth it?
The scientific conclusion seems to be no.
I have heard discussed in many places (Ben Greenfield talks about them) - whilst they have been shown to potentially have some respiratory benefits, what they do NOT do is actually have the effects seen by altitude, primarily increased blood volume and red blood cell count. Indeed they have been shown to be less effective at boosting these benefits than heat training (jumpers on the turbo anyone??) or doing light stretching/ Yoga in a sauna!
I was a bit dubious about them and guess your reply confirms it. many thanks