Journal Title (Medline/Pubmed accepted abbreviation): Int J Sport Nutr Exerc Metab
doi (if applicable):
Summary of background and research design
Hypothesis: The authors did not state a specific hypothesis. However, there were two aims to the study: 1) to determine the effects of fluid restriction or ad libitum consumption of water or a sports drink on basketball performance; 2) to assess the relationship between athletes’ knowledge about hydration and fluid replacement with their behavior in a real training situation.
Subjects: There were 12 male basketball athletes (14-15 y) that all belonged to the Portugese under-15 national basketall team who participated in the study.
Experimental design: Randomized crossover
Treatments:Fluid restriction, ad libitum water intake (3.8 mg sodium/L), 8% carbohydrate sports drink (540 mg sodium/L).
Protocol:Subjects completed three 90-minute training sessions, each followed by a 30-min performance evaluation drill. The subjects were assigned to either fluid restriction, water, or sports drink during the 90-min training session, administered in random order. Fluid intake was measured in the latter two conditions. The athletes were not blinded to the identity of the drinks and no attempts were made to match flavors of the water and sports drink. Diet was uncontrolled. Before the 90-min training session, the body mass of each athlete was measured. Basketball performance was evaluated by “around the world” shooting percentage within the 2- and 3-point range lines, free throw shooting percentage, time required to complete suicide sprints, and time required to complete a defensive “zig-zag” drill. After the performance evaluation drill, body mass measurements were again obtained, a urine sample was collected, and ratings of perceived exertion and beverage acceptability were elicited from the subjects. Subjects also completed questionnaires to assess fluid intake knowledge and behaviors.
Summary of research findings
- In the fluid restricted condition, body mass loss (2.46 %) was significantly greater than for either the water (1.08%) or sports drink (0.65%).
- Ratings of perceived exertion were significantly lower (P<0.01) for the sports drink versus the fluid restricted condition. There were no significant differences between the water and fluid restricted conditions or between the water and sports drink conditions.
- Fluid intake and beverage acceptability were not different between the water and the sports drink conditions.
- Basketball performance was unaffected by the hydration condition in each of the 5 basketball performance evaluation drills.
- The Spearman correlation coefficients were 0.56 for knowledge score vs. behavior score, 0.75 for behavior score vs. fluid intake, and 0.76 for knowledge score. However, for some behaviors, there was a large gap between knowledge and practice. For example, 75% of the athletes knew that weighing themselves before and after practice is a good way to determine how much fluid to consume. However, 16.7% actually performed this practice.
Interpretation of findings/Key practice applications
Although the fluid restriction did not statistically impair basketball performance relative to the other two conditions, the 2-point shooting percentage was ~60-61% in the water and sports drink conditions vs. 55% in the fluid restricted condition. Similarly, only the sports drink condition resulted in a 3-point shooting percentage above 40% (42.5% vs. 36-38% in the water and fluid restricted conditions). These types of improvements might have been statistically significant with a larger sample size. The first priority should be for the athletes to have ad libitum access to fluids, be it water or sports drinks.
There were no detrimental effects of using the sports drink, and the sports drink was the only condition to improve ratings of perceived exercise vs. the fluid restricted condition. Given these observations, coupled with the marginal but not statistically significant improvements in shooting performance with the sports drink vs. water or fluid restriction, ad libitum use of a sports drink might be preferable to plain water in this type of population.