When you’re cycling, numbness can begin in your buttocks and work its way down your thighs. The tingle can also start between your toes and work its way up your legs. Numbness in your lower extremities can frequently be attributed to a poor bike fit or badly fitting shoes. To improve blood flow and relieve stress on your glutes, the muscles in your buttocks, stand on your pedals and stretch your legs every 10 to 15 minutes of your cycling workout.
Does Your Bike Fit?
Based at Oregon’s Mid-Columbia Medical Center, physical therapist Anna Saltonstall treats many cyclists for problems with their hamstrings. Poor bike fit is one of main reasons for cycling injuries, which are preventable, says Saltonstall in the December 2008 issue of “Bicycling.” If you’re feeling numbness in your legs when cycling, your saddle may be exerting too much pressure on your sciatic nerve, which runs downward from the back of your pelvis through your hamstrings and calves and ends at your feet. A saddle that doesn’t fit your body puts too much weight on this nerve as well as on your blood vessels.
Comfort in the Saddle
Even if your bike is the correct size, your saddle position and shape may cause various problems, including numbness. A saddle that is too high shifts your weight off the pedals, requiring you to overextend your hamstrings with each pedal stroke. If your saddle is positioned too far back, you’ll depend too much on your glutes and hamstrings for forward power. A saddle with excessive cushion can cause your sit bones to sink into the middle of the saddle, increasing pressure on your nerves and blood vessels. A narrow saddle can cause your sit bones to hang off the sides, putting stress on the tendons that connect your hamstrings to your pelvis. Bike manufacturers may be able to provide a piece of memory foam in which you can leave an imprint of your buttocks. This tool can help you determine the optimal saddle width and shape for your body.
An Eye on Your Feet
Cycling shoes that fit improperly or provide inadequate support can cause numbness that begins in your feet and threads up your legs. Shoes that are too small or tight will squeeze the nerves in the arch at the ball of your foot. Impingement of the tiny nerve branches between your little toes can also result in swelling, tingling and numbness. Long-distance cyclists in particular can experience compression of the nerves under their feet. Allowing your feet some room to breathe by selecting wider shoes or loosening your shoelaces or straps may resolve numbness that starts in your feet.
Numbness in your legs may be a symptom of chronic compartment syndrome, which occurs in seasoned cyclists who perform a repetitive motion over a long period of time. Different muscle groups are surrounded and contained by fascia, or layers of connective tissue, into what are known as compartments. Bleeding or swelling that takes place within a compartment can increase the pressure inside the compartment to the point where it hinders proper blood flow. Because nutrients and oxygen can't reach your muscles, this condition can damage your tissues.
Numbness or paralysis is indicative of permanent damage, according to Britain’s National Health Service. For cyclists, the risk of compartment syndrome is greatest in the buttocks, and the condition has the potential to damage the sciatic nerve. If you’re experiencing numbness accompanied by leg cramps during cycling workouts, see your doctor.