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It starts with a tingle in your big toe or pinkie finger. Before long, your foot, hand or entire leg has gone numb and you spend the rest of your ride squirming to get the feeling back, says Paraic McGlynn, director of applied cycling science at the Serotta International Cycling Institute. Most numbness issues are caused by poor bike fit. Here's how to adjust your setup so your extremities never fall asleep on a ride again.
Ill-fitting footwear is the root cause of most lower-extremity numbness. When shopping for shoes, consider their width and height in addition to numerical size, says McGlynn. "Shoes with more height allow for taller arches," he says. Shoes that are too small pinch nerves in your metatarsal arch at the ball of the foot. The arch will collapse if it's not adequately buttressed, so be sure yours have sufficient support.
"A long reach to your handlebar creates a wrist extension that pinches nerves," McGlynn says. To determine your correct reach, ask a friend to watch you spin on a trainer. When your hands are on the hoods, your elbows should be slightly bent and your arms should be perpendicular to your torso. Vibrations from aluminum handlebars can also rattle your hands to sleep. McGlynn recommends installing Bontrager BzzzKill dampers ($10/pair) to absorb road chatter.
Leaning forward on your saddle compresses the perineal nerves (in the soft area between your groin and butt), which cuts off blood flow and feeling. First check your saddle tilt, says McGlynn. The top should be parallel to the ground, which allows your sit bones to carry most of your weight. Next, check your handlebar reach as described above; a long reach rotates your hips forward and transfers weight to your perineum.
A saddle that's wrong for your body can place excess weight on nerves and blood vessels, numbing you from your hips down, so test-ride a few with varying shapes and thicknesses. If you still experience numbness and loss of power after dialing in fit and gear, you may have iliac artery impingement, a condition that restricts blood flow to the legs, McGlynn says. The affliction is rare, but can turn up in cyclists who train in aggressive and time-trial positions. A 2004 study in Sports Medicine found the condition in 20 percent of elite cyclists surveyed. If rest and a more relaxed position fail to solve the problem, see your doctor.
Fit specialist Paraic McGlynn warns that not all numbness can be remedied with position adjustments and may require medical help. Sometimes, a spinal condition—such as a herniated disc, spine misalignment or disc degeneration—is the culprit. When these problems occur in the lumbar (lower, inward-curving) spine, they often cause lower-extremity discomfort or numbness. When in the upper spine, they affect your arms, shoulders and hands.