Well, I wasn’t sure what to expect when I first started using the powerbreathe, particularly as I am asthmatic. Although it affects me less now than it used to when I was a child, I still have trouble doing harder interval sessions on my bike and even heavier and more intense gym sessions can make me more breathless than I'd expect. I figured the powerbeathe would either kill or cure me!! I typically do CV work twice a week on my bike, which is mostly endurance work, but more recently I've included intervals. I also do weights in the gym 2 -3 times per week which is a combination of weight lifting and weight training. I was advised by the powerbreathe team not to use it for the first week, as I was recovering from a chest infection, so I started using it 4 days ago. Initially I found it difficult even on the lowest setting. Inhaling was difficult and also I felt it in my costo-vertebral joints (rib joints round the side of my spine). I managed about 12 breathes and stopped. I've used it twice a day since then for 4 days and it continues to be difficult to be honest. I'm very interested to see how that changes over time. I am doing more breaths now I'm up to about 20. As yet I haven’t noticed any difference in my training or daily life.