With the mountain bike on Tenerife
Tenerife is very popular with professional cyclists because they can keep their bodies in shape here even in winter. For me as a normal athlete, cycling on the island was not a big issue, because with these gradients it is just a torture to get up the mountains. But now there are ebikes and they allow everyone to ride even on these inclines, which makes a lot of fun. Some of the routes are a bit more demanding, but they are still doable for me as an average athlete. There are now several rental stations on the island and I can recommend everyone to give it a try.
The paths in the south of the island are much stonier than in the north. A helmet is recommended, which, by the way, is compulsory outside built-up areas in Spain.