Does anybody know any good way to boost my vital capacity? My total expiratory respiratory volume is just over 6 litres which is above average, but I want to get it pretty damn high. I'm aware of the "lung trainers" you can buy for £50+ but I'm on a fairly tight budget. So are there any exercises which help build up vital capacity which don't involve buying equipment or going to pilates etc? I was thinking something like blowing up inflatable beach balls or balloons may strengthen them and build them up but I'm not sure if there's enough opposing force from the inflatable to make it efficient. Are there any experts in respiratory physiology on here who can give me advice?