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It's not always a question of fit. Adjusting fit will solve the problem for many on the short rides typical of commuting. On rides longer than an hour, the pronated wrist required to grip flat bars can cause compression of the ulnar nerve. Pronation is twisting your wrists so your hands are knuckles-up. Ulnar nerve compression is a major cause of hand numbness. Changing hand positions often can alleviate this--but wait. How do you change your grip position using flat bars. There's a reason why drivers are taught to hold the steering wheel at 10 and 2 o'clock, and why the control yoke on airplanes has vertical grips. A neutral, rather than pronated, wrist position tends to avoid ulnar nerve compression. Drop bars allow a neutral wrist position when you hold them on the brake hoods, or the drops---with one catch. Putting too much arm/hand pressure on the bars (which results from both poor fit and poor fitness) can cause the wrists to bend inwards, increasing pressure on the ulnar nerve. One thing you'll see riders do is switch their hands from the hoods or drops to the flat part of the bars next to the stem. The multiple hand positions offered are the big advantage of drop bars over flat bars on long rides. You will see very, very few riders on rides of longer than, say, 30 miles riding flat bars.
[h=2]What causes ulnar nerve injury?[/h] There are many causes of ulnar nerve injuries, including pressure, trauma and illness. In some cases, ulnar nerve injuries may arise without a known cause.


The most common cause of ulnar nerve injury is extended pressure on the ulnar nerve, known as ulnar nerve entrapment. As the ulnar nerve travels from the shoulder to the hand, it passes through two tunnels of tissue, the cubital tunnel behind the elbow and Guyon’s canal in the wrist. Both tunnels are common locations at which the ulnar nerve can be compressed and injured. The ulnar nerve may also be compressed at the neck or beneath the collarbone.


Entrapment of the ulnar nerve may result from swelling of soft tissue, cysts, or damage to the bones in the arms. Bone damage causing ulnar nerve injuries include arthritis, elbow dislocations, elbow and wrist fractures, and bone spurs. Repetitive motions of the arm and hand, extensive bending of the elbow, and long-term pressure on the palm of the hand may also cause ulnar nerve injuries.


Ulnar nerve injuries may also be the result of direct trauma to the nerve. Finally, any whole body illness that is known to cause nerve damage, such as diabetes or hypothyroidism, can affect the ulnar nerve.
[h=2]What are the risk factors for ulnar nerve injury?[/h] A number of factors increase the risk of developing ulnar nerve injury. Not all people with risk factors will get ulnar nerve injury. Risk factors for ulnar nerve injury include:

• Activities in which your elbow or wrist is bent or twisted for prolonged periods
• Alcohol abuse
• Brachial plexus injury (injury to the bundle of nerves that transmit signals from the spine to the shoulder, arm and hand)
• Diabetes (chronic disease that affects your body’s ability to use sugar for energy)
• Elbow and wrist abnormalities
• Hypothyroidism (underactive thyroid)
• Nerve entrapment or compression, such as of the ulnar nerve in the arm
• Rheumatoid arthritis (chronic autoimmune disease characterized by joint inflammation)
• Sleeping positions that put pressure on your ulnar nerve

[h=3]Reducing your risk of ulnar nerve injury[/h] You may be able to lower your risk of ulnar nerve injury by:

• Avoiding positions that put pressure on the elbow or inside of the arm
• Keeping your elbow and wrist straight while sleeping
• Limiting activities that require the elbow or wrist to be bent for a prolonged period