title: Branched-chain amino acid supplementation and human performance when hypohydrated in the heat.
abstract: The serotonin system may contribute to reduced human performance when hypohydrated in the heat. This study determined whether branched-chain amino acid (BCAA) supplementation could sustain exercise and cognitive performance in the heat (40 degrees C dry bulb, 20% relative humidity) when hypohydrated by 4% of body mass. Seven heat-acclimated men completed two experimental trials, each consisting of one preparation and one test day. On day 1, a low-carbohydrate diet was eaten and subjects performed exhaustive cycling (morning) and treadmill exercise in the heat (afternoon) to lower muscle glycogen and achieve the desired hypohydration level. On day 2, subjects consumed an isocaloric BCAA and carbohydrate (BC) or carbohydrate-only drink during exercise. Experimental trials included 60 min of cycle ergometry (50% peak oxygen uptake) followed by a 30-min time trial in the heat. A cognitive test battery was completed before and after exercise, and blood samples were taken. BC produced a 2.5-fold increase (P < 0.05) in plasma BCAA and lowered (P < 0.05) the ratios of total tryptophan to BCAA and large neutral amino acid. Blood prolactin, glucose, lactate, and osmolality were not different between trials but increased over time. Cardiovascular and thermoregulatory data were also similar between trials. BC did not alter time-trial performance, cognitive performance, mood, perceived exertion, or perceived thermal comfort. We conclude that BCAA does not alter exercise or cognitive performance in the heat when subjects are hypohydrated.
authors.affiliation: U. S. Army Research Institute of Environmental Medicine, Thermal and Mountain Medicine Division, Kansas St., Natick, MA 01760-5007, USA. samuel.cheuvront@na.amedd.army.mil
authors.forename: Samuel N
authors.initials: SN
authors.lastname: Cheuvront
authors.forename: Robert
authors.initials: R
authors.lastname: Carter
authors.forename: Margaret A
authors.initials: MA
authors.lastname: Kolka
authors.forename: Harris R
authors.initials: HR
authors.lastname: Lieberman
authors.forename: Mark D
authors.initials: MD
authors.lastname: Kellogg
authors.forename: Michael N
authors.initials: MN
authors.lastname: Sawka
mesh_terms: D000328:Adult; D000597:Amino Acids, Branched-Chain / Q000008:administration & dosage*; D003681:Dehydration / Q000188:drug therapy* / Q000209:etiology / Q000503:physiopathology*; D019587:Dietary Supplements; D006359:Heat Exhaustion / Q000150:complications / Q000188:drug therapy* / Q000503:physiopathology*; D006801:Humans; D008297:Male; D010807:Physical Endurance / Q000187:drug effects*; D005082:Physical Exertion / Q000187:drug effects; D011597:Psychomotor Performance / Q000187:drug effects*; D016896:Treatment Outcome
chemical_list: D000597:Amino Acids, Branched-Chain