ADDING POLYLACTATE TO A GLUCOSE POLYMER-SOLUTION DOES NOT IMPROVE ENDURANCE

Polylactate (PL), a semi-soluble amino acid/lactate salt, is a newly d eveloped carbohydrate supplement purported to increase endurance. Our purpose was to determine if the addition of PL to a glucose polymer so lution (GP) extends exercise time relative to a pure GP solution. In a double blind and random crossover design, 5 subjects exercised twice to exhaustion at 70% of VO(2)max. During the trials, they consumed GP or a GP/PL mixture at the rate of 0.3 g carbohydrate per kg of body wt in a 7% solution every 20 min until exhaustion. The GP/PL mixture con tained 6.25 g GP to 0.75 g PL per 100 ml of water. Mixture composition was critical because PL, as supplied by the manufacturer and under ou r experimental conditions, produced severe gastro-intestinal efflux in concentrations greater than or equal to 2.5%; PL was tolerable in con centrations less than or equal to 0.75%. At 20 min intervals, we measu red VO2, respiratory exchange ratio, heart rate, and perceived exertio n. At 30 min intervals, we measured serum glucose, insulin, free fatty acids, and glycerol as well as whole blood lactate and pH. We found t hat the addition of PL to a GP solution had no measurable physiologica l or performance effects.