Coconut Water Does Not Improve Markers of Hydration During Sub-maximal Exercise and Performance in a Subsequent Time Trial Compared with Water Alone.

The purpose of this study was to compare markers of hydration during submaximal exercise and subsequent time trial performance when consuming water (PW) or coconut water (CW). There was also a secondary aim to assess the palatability of CW during exercise and voluntary intake during intense exercise. 10 males (age 27.9 ± 4.9 years, body mass 78.1 ± 10.1kg, average max minute power 300.2 ± 28.2W) completed 60-min of submaximal cycling followed by a 10-km time trial on two occasions. During these trials participants consumed either PW or CW in a randomized manner, drinking a 250 ml of the assigned drink between 10-15 min, 25-30 min and 40-45 min, and then drinking ad libitum from 55-min until the end of the time trial. Body mass and urine osmolality were recorded preexercise and then after 30-min, 60-min, and post time trial. Blood glucose, lactate, heart rate, rate of perceived exertion (RPE; 6-20) and ratings of thirst, sweetness, nausea, fullness and stomach upset (1 =very low/none, 5= very high) were recorded during each drink period. CW did not significantly improve time trial performance compared with PW (971.4 ± 50.5 and 966.6 ± 44.8 s respectively; p = .698) and there was also no significant differences between trials for any of the physiological variables measured. However there were subjective differences between the beverages for taste, resulting in a significantly reduced volume of voluntary intake in the CW trial (115 ± 95.41 ml and 208.7 ± 86.22 ml; p < .001).