Loosing out on mitochondria if you cycle instead of running for zone 2?

Hi people,

I am really hesitant in opting for a bike erg for endurance for a very simple reason: Compared to running (or even the assault bike or rowing) you train a much lower percentage (~70-75% in running vs ~40-45% in cycling) of your muscles, therefore missing out on a lot of mitochondrial biogenesis in many parts of the body.

I get that if your joints can't take running, you'll have to adapt to that.

However, I rarely see any concerns about cycling for zone 2 using less muscle and therefore providing considerably smaller stimulus per time invested.

What are your thoughts about that?