hmm its interesting we all know at higher altitudes theres less oxgyen in the air now when you train at higher alts your making your body work the same as you would at sea level but with less oyxgen so most people feel run down faster do to there being to much latic acid being built up (oxygen feeds red blod cells and removes waste aka c02) now when people return to sea level theres so much more oxygen in the atomosphere the body can now use this (like putting NOS in a car ) see the jake sheilds fight where he got done using canned oxygen so the more oxygen you have in your blood the better harder longer faster you can be and in recovery sense you recover alot faster from fatiuge and general soreness (faber uses a oxygen tank for recovery and rogan has a o2 pump in his isolation tank for these purposes ) now what bas ruttens 02 trainer does is train the diaphram so work more by restricting air flow and causing these muscles to work more and pull more air into your lungs so the more air you have the more oxygen you are getting now the tent thing looks to be the most legit for high att training and removing oxygen from the air giving you that high att effect the bike one looks to do both remove oxygen and force your diaphram to work harder i'm going to get a o2 trainer when they are released for fitness and band stuff and try and find a oxygen pump to give me more oxygen in my blood or just some canned air in the gym bag sorry if i rambled guys i find it interesting thats all