The effects of ingesting polylactate or glucose polymer drinks during prolonged exercise.
Level 2 - randomized trial
Double-blind balanced crossover clinical trial
PubMed 1844999 · doi:10.1123/ijsn.1.3.249
What was done
Five trained, fasted male cyclists completed three 180-minute cycling bouts at 50% VO2max in a double-blind, balanced-order crossover trial. Participants ingested one of three drinks 5 minutes before exercise and every 20 minutes during exercise: a 7% polylactate solution (80% polylactate, 20% sodium lactate), a 7% glucose polymer solution (maltodextrin), or an aspartame-sweetened water control. Venous blood samples and physiological measures were obtained at rest and every 20 minutes during exercise.
What was found
The abstract reports no numerical values, standard deviations, or effect sizes. Polylactate and glucose polymer produced generally similar physiological responses, except that blood pH and bicarbonate (HCO3-) were higher with polylactate. No differences among treatments were observed for perceived exertion, heart rate, oxygen consumption, blood lactate, electrolytes (sodium, potassium, chloride), rectal temperature, or skin temperatures.
Why it matters
This study provides preliminary evidence that polylactate may serve as an alternative energy substrate during prolonged endurance exercise with the potential added benefit of enhancing blood buffering capacity.
Limits
The sample size is extremely small (n = 5) and limited strictly to trained, fasted male cyclists at a single low-to-moderate intensity (50% VO2max). The abstract reports no numerical data, confidence intervals, or p-values, and direct measures of athletic performance (such as time-to-exhaustion or time-trial power output) were not assessed.
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