Is there an article? Where?

I certainly think it is not healthy to run hard 7 days a week. But, there is less evidence that running a few days a week is unhealthy. Moderate "impact" may still be good.

The same is probably true with bicycles. Ride hard some, rest some.

Even the young top-tier athletes on the TDF complain about riding hard every day. Now, as an octogenarian, one might not be riding like the TDF, but a mix of activities, and rest is still reasonable.