INDUCTION OF LOCALIZED LEG CRAMPS USING A RUN/SWIM PROTOCOL

Abstract

Athletes, especially swimmers, experience painful, localized muscle cramps in the lower extremities during training and competition. The cause of exercise-induced muscle cramps remains elusive. To explore the causes of muscle cramping, we tested cramp reproducibility during a specific exercise protocol. Five tri-athletes (four men, 1 woman) with a history of periodic exercise-associated muscle cramps completed two identical trials of a run/swim protocol on two separate occasions. The protocol consisted of a 45-minute treadmill run at 75–85% HRmax, followed by an hour-long swim workout. Beverage was withheld from subjects during the entire session. During the swim, subjects reported time of onset, the location, and severity of the muscle cramps on a 1–10 scale. Pre- and post-run nude body weights were measured to assess fluid loss during the run portion. Pool water temperature was recorded with a lab thermometer, as water temperature has been implicated in exercise-associated muscle cramp etiology. Four of the five subjects experienced localized muscle cramps in both trials and all subjects complained of muscle cramps in at least one trial. Severity and duration of muscle cramps varied widely among subjects but did not vary within subjects. Pain ranged from very slight spasms in the toe to severe cramping of calves, quadriceps and hamstrings. Average percent body weight lost during the run was 1.7*0.3% in the first trial and 1.7*0.4% in the second trial. Results of this investigation lead us to believe that exercise-associated muscle cramps can be reproduced with a specific exercise model; the time of onset and severity of cramps may vary with environmental conditions, degree of muscle fatigue due to type and intensity of exercise, and electrolyte loss, all of which warrant further investigation.