Thanks a lot to both of you.
It all makes perfectly sense to me. At this stage it is important to develop both the aerobic base, technique and speed. It is interesting though that the immediate response cross country coach (experienced) based on the test results was to introduce more high intensity in order to raise/develop the threshold levels. Young athletes recover fast and in that respect are responsive to high intensity training, so I kind of find it kind of reasonable. As you say Scott, it may result in a “short term” progress, but not necessarily be beneficial in the longer run. Interestingly there are a large body of research literature on high intensity training for adult endurance athletes but the research on the short and long terms effects of high intensity training on young athletes are sparse. The research in this last category show varying/inconclusive results the effects of high intensity training. There was some positive indications on running velocities and performance at various thresholds and others like that, but not very significant compared to alternative training protocols. More importantly I think, there is a lack of research on the more long term effects of high intensity training for young athletes. Would it be beneficial for their long term development, to what extent and volume? Your approach and arguments are very reasonable and appreciated.