Loss of leg coordination while running as a task-specific focal dystonia distinct from runner's dystonia
An executive summary of findings on loss of leg coordination while running
Loss of leg coordination while running is the working term for a rare neurological problem that occurs in long distance runners. It is characterized by a gradually increasing sensation of tightness, weakness, and poor coordination in the muscles of one leg that occurs only while running—stopping to walk or stand still all but eliminates the symptoms. Runners with loss of leg coordination cannot point to a specific area of pain; rather, there is a more general feeling of tightness, vague aching, and an overwhelming sense of something being "off" with the functioning of the affected leg when they run. Further, classic signs of neurological injury, like numbness, shooting pain, or a "pins and needles" sensation, are absent.
These symptoms are also highly specific to running. Other activities, even cyclical and highly aerobically demanding ones like using an elliptical or riding a bike, do not reliably recreate the symptoms. The loss of coordination sensation is typically localized to the muscles which are the prime movers of the legs: the calves, the hamstrings, the quadriceps, and the gluteal muscles. Despite the weak, uncoordinated sensation while running, absolute muscular strength is normal.
In most cases, running longer, faster, and on flat surfaces exacerbates the problem. Some runners find they lose coordination with any kind of running, but most are able to run at an easy pace on rough terrain (e.g. on trails or over cross-country). Short intervals of fast running are not usually a problem, but longer intervals at fast speeds and especially fast continuous runs and races bring on loss of leg coordination more rapidly. Ceasing a run makes the loss of coordination sensation go away almost immediately, but some lower leg muscular tightness can persist for a few days after a particularly bad episode.