Originally Posted by Carbonfiberboy

I notice that neither I nor anyone else actually answered your questions. What's probably going on is that you were not clearing lactate (the burn) as fast as you were making it. A certain amount of lactate is good for performance, but too much limits performance. Your body will naturally get better at clearing it when you push it as you did on that climb. It's not really a strength or aerobic capacity issue, it's a metabolic issue at the cellular level. Takes time for your muscle cells to change, but they will. You had to stop to give your body a chance to clear a little of it. Soon you won't have to stop, it'll just keep up as long as you don't demand too much from it. Technically, your power at lactate threshold will go up. 15-20 minute intervals at lactate threshold is the standard training methodology.