[Scott Johnston]

Radu has pretty much nailed it.

It is related to the “economy” or the energy cost of locomotion.  I happen to know that Brian is taking up Nordic skiing after a 30+ year hiatus. Nordic skiing is one of, if not the most, technically demanding endurance sports.  His current level of technical proficiency, especially in the skating technique is low enough that it is costing him significantly more energy to ski than it is to run.

Improving/refining technique in skiing is something that takes a lot of time and PERFECT practice.  If you practice poor technique, all you do is get really good at doing it wrong.  With only a handful of days on snow so far, this technique deficiency is totally understandable.

Major, like double-digit, gains in performance can be had by improving skiing or running economy.  Whereas adding either more volume or more intensity can actually have the opposite effect on performance if you have poor technique.

Say you add high-intensity intervals to your training in hopes of increasing your endurance performance.  But your technique gets worse when doing those intervals.  You are perfecting poor technique.  You are engraining inefficient movement patterns into the motor nervous system that can be hard to unlearn.

Scott