I posted a question like this a while back when I first got my road bike (I was riding my more upright hybrid before that). Both my elbows were hurting after about 30/40 miles. Just getting stiff and sore in that position and hard to bend. I knew I wasn't "locking" them in a fully extended position, so I checked with the LBS where I bought the bike and they suggested a shorter stem (so did my helpful friends here at the forum ). I ended up putting an adjustable MTB stem on so I could get a shorter reach and a higher position. That helped tremedously but there was an element of my arm muscles getting stronger to hold me in that position as well. They feel fine now!