Comparison of coconut water and a carbohydrate-electrolyte sport drink

Comparison of coconut water and a carbohydrate-electrolyte sport drink

Kalman, D. S., Feldman, S.,Krieger, D. R., & Bloomer, R. J. (2012). Comparison of coconut water and acarbohydrate-electrolyte sport drink on measures of hydration and physicalperformance in exercise-trained men. Journal of the International Society of Sports Nutrition, 9(1).

 The purpose of this study was to investigate the effects of two different forms of coconut water (concentrated and not from concentrate) and a carbohydrate-electrolyte sport drink on measures of hydration status and physical performance in exercise-trained men. 

 The study used 12 exercised trained men who were eligible to participate after completing a healthy history questionnaire and physical examination. All the subjects were instructed to maintain their pre-study exercise program throughout the course of the study,with the exception of refraining from exercise during the 24 hours prior toeach test day. On initial screening day, height, body mass, heart rate, and blood pressure where allrecorded for baseline. On each ofthe four test days, subjects reported to the lab in the morning following anovernight fast (no food or beverages other than water were allowed aftermidnight). After baseline assessments, subjects were provided with a standardized breakfast consisting ofa bagel, one tablespoon of cream cheese, and up to 470 mL of water. Sixty minutes after the conclusion ofthe standardized breakfast, subjects performed the dehydrating exercise test. This test consisted of two, 30-minutesbouts of walking/jogging, interspersed with a 10-minute rest period. Specifically, subjects walked/jogged at2. 3, 4, 5, 6 and 7 miles per hour on a motorized treadmill, using a grade of0% (five minutes of exercise was performed at each speed). Within minutes following the conclusionof the dehydration exercise test, subjects received their assigned condition(beverage). The study designinvolved a random order, single blind, cross-over assignment to one of the followingfour conditions: Supermarket brand bottled water, pure coconut water (VitaCoco), coconut water from concentrate, or a carbohydrate-electrolyte sportdrink. The amount of beverage was determined based on the total amount of body mass lost during the dehydratingexercise protocol using the equation 1300 mL .kg^-1 x kg loss = amount of beverage consumed (mL). Subjects were allowed 60 minutes toconsume the entire volume of beverage. Each condition was consumed on a different test day, with minimum offive days separating test visits. Performancetesting involved subjects walking on a motorized treadmill which remained on aconstant speed of 4.2 miles per hour throughout the test, however, every threeminutes they would increase the intensity by increasing the incline as follows:min 1-3, 0%; min 4-6, 2.5%; min 7-9, 5%; min 10-12, 7.5%; min 13-15, 10%; min16-18, 12.5%; min 19-21, 15%. Subjects exercised until volitional exhaustion and the total exercisetime was recorded. Inaddition to the measure of total exercise time obtained in the performance testdescribed above, the following variables were used as outcome measures: bodymass, plasma osmolality, urine specific gravity, and subjective measures(thirst, bloatedness, refreshed, stomach upset, and tiredness). Subjective measures were assessedimmediately, 60 minutes, 120 minutes, and 180 minutes follow the dehydratingexercise test. 

 Overallthe study found that subjects lost approximately 1.7 kg during the dehydratingexercise testing and regained this amount in a relatively similar mannerfollowing consumption of all conditions. No significant differences were noted between coconut water, coconutwater concentrate, and sport drink for any measures of fluid retention. Regarding exercise performance, nosignificant difference was noted between bottled water, coconut water, coconutwater concentrate, and sport drink. In general, subjects reported feeling more bloated and experiencedgreater upset stomachaches with the coconut water and coconut water concentrateconditions. 

 Thefirst critique of this study was the lack of obtaining nutritional intakerecords of all the subjects during the study. I believe it would be valuable information to determine ifany supplements were being used during the study or if any macronutrients couldhave been an outside factor to results. Another critique of the study was measuring performance exercise testingwith volitional exhaustion. Ibelieve that motivation could play a role in the perception exhaustion;therefore, time trial test should be applied in further studies as stated inthe discussion section of the article. 

 Chiefly,the information obtained from this study could be used by athletes and coacheswhen determining preferences in rehydration protocol.