Coconut water does not improve markers of hydration during sub-maximal exercise and performance in a subsequent time trial compared to water alone

The purpose of this study was to compare markers of hydration during sub-maximal 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 sub-maximal cycling followed by a 10-km time trial on two occasions. During these trials participants consumed either PW or CW in a randomised 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 pre-exercise 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 to PW (971.4 ± 50.5 and 966.6 ± 44.8 seconds respectively; P=0.698) 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 <0.001).