Have a quick question about low volume, high intensity training for long distrance/Ironman racing vs. more traditional high volume, medium/low intensity training.

My work/travel schedule is all over the place and when I was training for IMMT this year, I peaked out at 6 hours of training per week, and most weeks were 4-5 hours per week of training. Since my work schedule didn't allow for a more traditional training regimen, I spent my few precious hours of training at very high intensity, including alot of high intensity interval training on various hotel treadmills across North America.

Based on any rational measure, I was way undertrained for an Ironman race, but I finished sub-15 hrs. My stretch goal was sub-14 hrs and if it wasn't for the weather, I think I might have been able to do it, but c'est la vie. When I did my 2 previous IM races, I followed a more traditional high volume, medium/low intensity training regimen - and my finish times were in the same ball park as this year's finish time at IMMT.

So, can somebody school me on the two approaches to training and how I should sketch out my training for next year. I imagine the optimal training is a mix of high intensity and moderate/low intensity training, but I would be interested to see what y'all think.

Thanks.