Oooh no! it's not related to muscle strength, it's probably caused by a squeezed nerve or something like that, quite similar to the carpal tunnel syndrome... Don't let it go unchecked.

My hypothesis for the cause of my elbow pain was that the stem was too long. Well according to the charts and to the length of my forearm, it's actually too short by one or two centimeters, but as the bike store guy said: it's just a standard value. Plus, I have long arms and legs but a short torso, so that may be the cause. Anyway he didn't have a shorter stem on stock for my bike so we decided to try something else for the moment: he reversed the position of the stem so that the handlebars are a bit higher (by something like 5 degrees). We'll see how that fares and if it doesn't work we'll order a new stem. If all else fails, I'll try wider handlebars. I too have noticed that my wrist is slightly tilted, but then all of the people I see have the same position and it doesn't cause them the same problem so I'll try different things...

After a few more hundred kilometers on the new bike I'll go into a full positioning session. It's a bit expensive for my bike budget right now but I think it's necessary if I want to ride and ride some more. I'm getting used to the position on the road bike and figuring out what hurts because I don't have the correct muscles in shape yet (these are fixing up by themselves as I ride) and what hurts because I'm not correctly seated on the bike.

I'm riding a few kms tonight, I'll keep you posted about the new configuration of the pain.