Great points being made and reiterated. I have personally seen the huge rewards of cross training and am dumb founded that it’s not more utilized amongst the top level, elite runners. I think it’s these wise tales we hear about it ruining your form or that you will turn into a triathlete ;)
In all seriousness, the aerobic abilities can be improved significantly from a higher volume of training obviously but except for a handful of biomechanical anomalies most of us can not maximize that with running alone. Cycling / elliptical can allow you to add in more volume and even pull from an additional pool of muscle fibers to build additional mitochondria.
I think the key is in periodizing the use and implementation. this athlete is doing plenty of specific training as he nears the competition and that training is also more the more intense sessions to prepare one to race well and maximize performance from the aerobic capacity built from hours an hours of long steady distance (but just not skating).
anyone who has read olbrecht and his work on swimming training will be familiar with the idea of first maximing aerobic capacity, and he argues that a swimmer should use additional strokes than just what they might race for developing aerobic capacity. Then, as one nears their peak performance, one will shift to focusing on aerobic power and this should be done with the specific stroke for a given performance. It’s similar here, and you use the training easier on the body to do more aerobic training. Then to translate that to race performance (aerobic power), focus on race specificity.
Someone brought up Ritz, and I think we can all agree that while he was injury prone, he still achieved what was once seen as unthinkable amongst American distance runners. Listen to him talk about his career and these accomplishments, and it’s clear that he often was following this process (albeit begrudgingly at the mercy of overcoming one injury after the next). Ritz would get hurt and then cross train like a man possessed on the bike and elliptical. From the sounds of it, he was doing hours of high end aerobic training that would not have been possible if he was just running. Then, once he was back healthy, he could get back to run specific training and only need a few weeks of running to run some incredible performances.
Perhaps this is just utter blasphemy and heretical to say but what if that is why he ran such incredible performances. What if he could not have developed his aerobic system to the sam extent if he was always healthy and just running? If he was doing 20+ hours of high end aerobic training when injured, that would be at least double the total aerobic training he would have done just running alone. Plus, the run training would have been far less “high end”. This is not to say the running performances were achieved with the cross training alone, but maybe if you could utilize this low impact training and really get after it while still sprinkling in some running, you can then launch into a 6-12 week race specific phase, focused on running at a level that you couldn’t have otherwise achieved?
I can speak from experience that my best running came after a 3-6 month period of being unable to run much due to injury. I training twice per day on the bike / elliptical at a steady clip along with two super intense sessions per week doing 15ish hours per week, and then I transitioned to doing 50 - 60ish miles per week and two intense running workouts each week and ran PRs from the mile to the half marathon over that summer. It worked.
There is no substitute for the run specific training, and I would not have been able to have much to show for my fitness before a few weeks of consistent running but that’s all it took, just a few weeks.