four times the usual rate in maximum voluntary con- traction [4]. Approximately 1 in 3 adults experience night-time cramping of the calf-muscle [5], the most common type and location of cramp [6-8]. Despite the high prevalence of night-time calf-muscle cramps, it is not well understood why some people cramp and others do not. Currently, many interventions are available for preventing night-time calf-muscle cramps (e.g. quinine, magnesium, and muscle stretching, strengthening and