In plain English could somebody explain this. When i practise breath holds, i find that the first attempt goes to around the 2 min 30sec mark. I then rest for 2 min then go again, this one normally gets to around 3 min, the rest is repeated and so on. I find it takes around 4 attempts to hit my max, which now stands at around 4min 30sec, (my P.B. is now 4min 43sec). Any thoughts or advice would be much appreciated, cheers..