Letter to the Editor

Dear Editor,

Some of the serum sodium data reported in Table 1 by Dickson et al. (Int J Sports Med 2005; 26: 481 - 485) are not compatible with life or with the corresponding results for serum osmolality. It is also highly improbable that five of the twelve reported sodium results are equal to 135.86 mmol/l. There is also a significant flaw in their measurement of brain volume, in that any loss of fluid from the brain results the rapid movement of osmolytes from the CSF and serum into the brain. This serves to defend brain volume and limit fluid losses. Water loss and electrolyte uptake are likely to occur almost simultaneously, with the magnitude of brain water losses demonstrated to be only 35 % of expected, 30 minutes following osmotic opening of the BBB (Cserr et al. Am J Physiol 1987). It is likely that there was a marked redistribution of fluids to restore brain volume between the end of exercise and the time taken to complete the measurements, seriously confounding the results of the study.

Yours sincerely,

Arthur Strachan and Phil Watson