LAUSR

I have read the letter by Valenzuela et al. [1] regarding my review article entitled ‘‘Drinking strategies: planned drinking versus drinking to thirst’’ [2] and would like to address several misconceptions in the letter. Valenzuela et al. [1] state that my final advice in the review is to ‘‘...avoid drinking to thirst in order to prevent BW losses[ 2% during activities of high intensity or long duration ([ 1–2 h), or when exercising in warm/hot environments’’ [2]. However, this statement is not accurate, the recommendation is to employ a tailored drinking program to avoid potential thermoregulatory, cardiovascular, and exercise performance impairment (2% body weight loss), particularly in the conditions described. This recommendation is particularly true for individuals with high sweat rates, who are heat-acclimatized or for those whose primary concern is optimal performance. Valenzuela et al. [1] state that I describe incidences of hyponatremia as ‘‘rare,’’ which is also inaccurate. The situations described as ‘‘rare’’ in the review are documented cases of hyponatremia where individuals have over-consumed fluid ‘‘according to thirst’’ [3]. Valenzuela et al. [1] state that hyponatremia can be present without weight gain (hypovolemic hyponatremia). However, the conditions where it can manifest (accumulated sodium loss due to continual sweating over hours/days of continuous work/exercise; consumption of hypotonic fluid) are uncommon for most exercising/competing individuals. While hyponatremia is not a focus of the review, the recommendation to never consume so much fluid that weight is gained is made throughout the review and supported by both papers [4, 5] cited by Valenzuela et al. [1]. In regard to exercise performance, the review acknowledges that performance decrements reported in some laboratory studies may be exaggerated [2]. Most individuals are not in a state of 2–4% body mass loss when they commence exercise/competition and dehydration takes time to accumulate. As shown by a review of dehydration/exercise performance studies [6], 68% of reported observations were of impaired exercise performance (p\ 0.05) by dehydration of C 2% body mass. As demonstrated in the review, the accumulation of sweat losses while running over a range of distances (5–42 km), in two environments (22 and 30 C), only approaches 2% body mass loss around 21 km for faster runners in warmer environments. Thus, to avoid body mass losses of 2% or greater, the recommendation for a tailored drinking program for activities/competition of long duration (90 min to 2 h), at high exercise intensity, in warm/hot environments is supported. The review acknowledges that drinking-to-thirst would certainly be sufficient during activities of short duration, particularly in cooler conditions [2]. In fact, the metaanalyses of exercise-induced dehydration cycling performance studies [7, 8] cited by Valenzuela et al. [1] further support this point, as nearly all of the studies in the metaanalyses were cycling time-trials of 90 min or less, performed in cool/warm conditions with high wind speeds. & Robert W. Kenefick [email protected]