AVP and Hyponatremia: Some authors have hypothesised that one condition may cause the other [4–6], as rhabdomyolysis may bring about exercise-associated hyponatremia through arginine vasopressin secretion [4, 7], stimulated by the increase of interleukin-6 and CK [8, 9], and exercise-associated hyponatremia may cause rhabdomyolysis through changes in intracellular K+ and/or Ca++ concentrations, which reduce cell membrane stability and cause muscle cell injury [10].