I only use shorter L2 sessions to bridge harder sessions. While there are lots of polarized studies out there that have fairly aligned results, I see them as a way to add TSS during a build without adding a ton of stress. If I switch 1 ride a week to 2hrs of L2 instead of a 1hr spin that is an additional ~60 TSS and while not a lot, is enough to increase training stress without adding too much risk. Otherwise, I can see them being useful if done to bridge harder sessions as long as you can recover because the half life of many of the primary adaptations of L2 riding are fairly short and it helps to keep plasma volume high and capillaries/mitochondria active and processing blood/fuel. Plus, I think most low volume riders are really not in danger of overtraining and it probably won't hurt them to add in more work. Cycling is still an aerobic sport. If you add in just 1hr of L2 a week for half of the year, that is an extra 26hrs of riding. An extra 50hrs/year is not trivial. Think long term.
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