While I have discussed numerous personal stories with a variety of our regular Winter Training participants, there is substantial independent, university based research to support the need to know both your LOW threshold (often referred to as aerobic threshold) as well as your HIGH threshold (previously considered the only threshold). The graphic below shows how the research has evolved over time. Also one of the many studies on training below T1 has proven the expansion of

The power and importance of building a good base at the start of any training plan can not be over-stated. None of the training that happens after base building will be as effective if the base is not secure, like the very foundation of a building. Weak or shallow foundation, and the entire structure is suspect. This is why the winter makes the best time to do this - no distractions of competition or competing interests outside (except for some ski slope time now and then),