Forearm pain during and after cycling I've been riding for a couple weeks after years of not sitting on bike in order to strengthen my health. I've been commuting to my work and school (12km/7.45 miles from my home) about three days a week and then resting/waiting (because of seasonal rains in my area). About three weeks ago I've started to feel ache in my right forearm in area highlighted in picture and it continues to ache for a couple more days when I lift something heavy or twist my hand or sometimes even without cause. After about ten days it has gone, but when I got on bike three days ago again, it has started again. Sometimes I also feel numbness or cramps in fingers in my right hand, but when I take off my hand of bike and stretch my fingers for a couple of seconds, it will go away.
Any suggestions what could be the cause of the forearm pain? I will see my local orthopedist in a week, but I don't trust him much as he is pretty lazy to even properly diagnose something. The only thing that has crossed my mind is that my handlebar is too low for me.
There are multiple possible causes for this kind of pain.

Of course, you should see a medical person in case something more serious is going on than our amateur diagnosis suggests.

In general, this is a kind of overuse injury. This can have different causes (and each would have slightly different symptoms). Part of the reason is that you've taken a break and those muscles are just not as strong as they used to be. Common causes are


The most common cause is your seat too high relative to the handlebars, leading you to put more weight on your forearms. This would be more common for mountain bikes and flat-bars, and seems more likely given the posted diagram.
Another cause to gripping too tightly. You could be gripping the handlebars too tightly, or trying to do too many jumps, etc. This can also be due to repeated hard braking.
You could be overstretching the tendons / muscles, by riding with your wrists low so that your hands are higher than your wrists, or with your wrists bent to the side so that each wrist is bent inwards or outwards. This is more likely on a road bike if you ride with your hands "on the corners" a lot. Or perhaps if the handlebars are too narrow.
Even stranger, it can be caused by pushing too hard on indexed gear levers. You would probably know if your enthusiastic gear changes were causing it. 


EDIT

Often the solution to this kind of problem is suggested by the diagnosis but requires some experimentation because the the result of a change can be hard to predict. Everything is interconnected, so changing one thing without full understanding can have unintended consequences. If you make changes yourself then be vigilant for other issues.

Taking the bike to your LBS to get them to check your position is recommended.