title: The influence of dietary manipulation on plasma ammonia accumulation during incremental exercise in man.
abstract: The influence of a pattern of exercise and dietary manipulation, intended to alter carbohydrate (CHO) availability, on pre-exercise acid-base status and plasma ammonia and blood lactate accumulation during incremental exercise was investigated. On three separate occasions, five healthy male subjects underwent a pre-determined incremental exercise test (IET) on an electrically braked cycle ergometer. Each IET involved subjects exercising for 5 min at 30%, 50%, 70% and 95% of their maximal oxygen uptake (VO2max) and workloads were separated by 5 min rest. The first IET took place after 3 days of normal dietary CHO intake. The second and third tests followed 3 days of low or high CHO intake, which was preceded by prolonged exercise to exhaustion in an attempt to deplete muscle and liver glycogen stores. Acid-base status and plasma ammonia and blood lactate levels were measured on arterialised venous blood samples immediately prior to and during the final 15 s of exercise at each workload and for 40 min following the completion of each IET. Three days of low CHO intake resulted in the development of a mild metabolic acidosis in all subjects. Plasma ammonia (NH3) accumulation on the low-CHO diet tended to be greater than normal at each exercise workload. Values returned towards resting levels during each recovery period. After the normal and high-CHO diets plasma NH3 levels did not markedly increase above resting values until after exercise at 95% VO2max. Plasma NH3 levels after the high-CHO diet were similar to those after the normal CHO diet.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Environmental and Occupational Medicine, University Medical School, Aberdeen, UK.
authors.forename: P L
authors.initials: PL
authors.lastname: Greenhaff
authors.forename: J B
authors.initials: JB
authors.lastname: Leiper
authors.forename: D
authors.initials: D
authors.lastname: Ball
authors.forename: R J
authors.initials: RJ
authors.lastname: Maughan
mesh_terms: D000136:Acid-Base Equilibrium / Q000502:physiology; D000328:Adult; D000641:Ammonia / Q000097:blood*; D001810:Blood Volume / Q000502:physiology; D004032:Diet; D004040:Dietary Carbohydrates / Q000494:pharmacology; D015444:Exercise / Q000502:physiology*; D006801:Humans; D008297:Male; D010101:Oxygen Consumption / Q000187:drug effects; D005082:Physical Exertion / Q000502:physiology; D013997:Time Factors
chemical_list: D004040:Dietary Carbohydrates; D000641:Ammonia