 This is a study involving 32 16 intervention, 16 control hemodialysis patients with frequent lower extremity cramps during treatment. Frequent cramping during dialysis treatments is defined as 1 or more episodes of lower extremity cramps during or after dialysis over the previous 2 weeks. Cramping frequency will be determined by chart notes. Muscle cramping is defined as contraction of the large muscle group of the lower extremities sufficiently painful to require intervention by the dialysis staff for relief. 