A couple of weeks ago my left elbow became very tender. The only change in my routine had been a couple of longer rides: 40 miles instead of my usual commute of 4-6 miles one way.
The pain is on the inner elbow (so that standing with my palms facing outward the pain is in that part of the elbow nearest my chest. With my arm outstretched and palm upward, there is pain with attempted flexion (like making a fist) against resistance. There is no pain when the palm is facing downward and the hand is flexed upwards against resistance.
Diagnosis? MEDIAL EPICONDYLITIS, also know as Golfer's elbow. These tendon/ligament injuries are often attributed to repetitive movements, which doesn't make sense for cycling.
What I think is happening is that the shocks and vibration not absorbed by the tires or front shocks travels up the arm and ends up at my locked elbow (I tend to ride with a straight arm). The wrists are slightly bent and just send the energy upwards. My right arm is protected because a few decades ago an injury left me with the inability to completely straighten and lock my right arm. So on the right side the vibration travels up and disipates or is absorbed the the large shoulder muscle. I need to ride with left my arm slightly bent. Or I could stop cycling for a few weeks (yeh, right, now that's going to happen)
note: not to be confused with "handlebar palsy" in which the vibration and shock injure the ulnar nerve, with symptoms along the length of the nerve and can include numbness or tingling, from the forearm to the 4th and 5th digits. Handlebar and/or seat adjustments help by decreasing the stretch of the arm.