Leg cramps—involuntary muscle spasms (contractions)—during a marathon can be very debilitating and painful. Runners commonly get them in the calves, hamstrings, and quadriceps muscles, and they often occur in the last few miles of a marathon or a long training run. There is much debate about what causes these cramps. Some current explanations are overexertion, dehydration, fatigue, and inadequate training, leading to altered communication from the nerves to the leg muscles.
Regarding exertion and dehydration: During longer runs, body temperature increases, which causes sweating, which in turn causes a loss of electrolytes—especially salt. Runners should drink adequately, including something like a sports drink that contains electrolytes, to counteract this loss. It’s hypothesized that as body heat increases over the course of a long run, blood volume decreases, which taxes the muscles and can lead to cramping. Runners can help avoid this syndrome by training for the race conditions, including temperature, hills and distance.
If cramps do strike you during the marathon, slow to a jog or a walk, but don’t sit down! Continuing to move will help the muscles relax. If walking is too painful, step off the course and do some stretches for the cramped muscle. You can try applying some deep pressure to the area and massaging the stiff muscle. When the muscle has relaxed, try to start running again slowly. You can also try a run/walk alternation for a few minutes to let the muscles start to gently contract. For severe cramping, visit a medical aid station along the course, where experts are trained to help runners manage serious cramping and get back out on the course.
After the race, refuel and hydrate thoroughly, make sure that you continue to walk to allow the muscles to relax and lengthen.
Julie Khan is a physical therapist in the HSS Rehab Department. She graduated from Columbia University with a Masters and a Doctorate of Physical Therapy. Her clinical interests include post-surgical sports-related injuries and running mechanics. She has completed more than 20 half-marathons and six marathons.