title: Acidosis, but Not Alkalosis, Affects Anaerobic Metabolism and Performance in a 4-km Time Trial.
abstract: This study aimed to determine the effect of preexercise metabolic acidosis and alkalosis on power output (PO) and aerobic and anaerobic energy expenditure during a 4-km cycling time trial (TT).
  
  
  
  Eleven recreationally trained cyclists (V˙O2peak 54.1 ± 9.3 mL·kg·min) performed a 4-km TT 100 min after ingesting in a double-blind matter 0.15 g·kg of body mass of ammonium chloride (NH4Cl, acidosis), 0.3 g·kg of sodium bicarbonate (NaHCO3, alkalosis), or 0.15 g·kg of CaCO3 (placebo). A preliminary study (n = 7) was conducted to establish the optimal doses to promote the desirable preexercise blood pH alterations without gastrointestinal distress. Data for PO, aerobic and anaerobic energy expenditure, and blood and respiratory parameters were averaged for each 1 km and compared between conditions using two-way repeated-measures ANOVA (condition and distance factors). Gastrointestinal discomfort was analyzed qualitatively.
  
  
  
  Compared with placebo (pH 7.37 ± 0.02, [HCO3]: 27.5 ± 2.6 mmol·L), the NaHCO3 ingestion resulted in a preexercise blood alkalosis (pH +0.06 ± 0.04, [HCO3]: +4.4 ± 2.0 mmol·L, P < 0.05), whereas NH4Cl resulted in a blood acidosis (pH -0.05 ± 0.03, [HCO3]: -4.8 ± 2.1 mmol·L, P < 0.05). Anaerobic energy expenditure rate and PO were reduced throughout the trial in NH4Cl compared with placebo and NaHCO3, resulting in a lower total anaerobic work and impaired performance (P < 0.05). Plasma lactate, V˙CO2, and end-tidal CO2 partial pressure were lower and the V˙E/V˙CO2 higher throughout the trial in NH4Cl compared with placebo and NaHCO3 (P < 0.05). There was no difference between NaHCO3 and placebo for any of these variables (P > 0.05). Minimal gastrointestinal distress was noted in all conditions.
  
  
  
  Preexercise acidosis, but not alkalosis, affects anaerobic metabolism and PO during a 4-km cycling TT.
authors.affiliation: 1Sports Science Research Group, Department of Physical Education and Sports Science, CAV, Federal University of Pernambuco, Recife, BRAZIL; 2Endurance Performance Research Group (GEDAE-USP), School of Physical Education and Sport, University of São Paulo, São Paulo, BRAZIL; 3Institute of Sport, Exercise and Active Living, College of Sport and Exercise Science, Victoria University, Victoria, AUSTRALIA; 4School of Medical and Health Sciences, Edith Cowan University, Joondalup, AUSTRALIA; and 5Human Performance Research Group, Academic Department of Physical Education, Technological Federal University of Parana, Curitiba, Parana, BRAZIL.
authors.forename: Carlos Rafaell
authors.initials: CR
authors.lastname: Correia-Oliveira
authors.forename: João Paulo
authors.initials: JP
authors.lastname: Lopes-Silva
authors.forename: Romulo
authors.initials: R
authors.lastname: Bertuzzi
authors.forename: Glenn K
authors.initials: GK
authors.lastname: McConell
authors.forename: David John
authors.initials: DJ
authors.lastname: Bishop
authors.forename: Adriano Eduardo
authors.initials: AE
authors.lastname: Lima-Silva
authors.forename: Maria Augusta Peduti Dal'molin
authors.initials: MAPD
authors.lastname: Kiss
mesh_terms: D000138:Acidosis / Q000150:complications / Q000503:physiopathology*; D000328:Adult; D000471:Alkalosis / Q000150:complications / Q000503:physiopathology*; D000077410:Aluminum Chloride; D017607:Aluminum Compounds / Q000097:blood; D054874:Athletic Performance / Q000502:physiology*; D001642:Bicycling / Q000502:physiology*; D002712:Chlorides / Q000097:blood; D004311:Double-Blind Method; D004734:Energy Metabolism / Q000502:physiology*; D005767:Gastrointestinal Diseases / Q000209:etiology; D006801:Humans; D006863:Hydrogen-Ion Concentration; D019344:Lactic Acid / Q000097:blood; D008297:Male; D017693:Sodium Bicarbonate / Q000097:blood; D013997:Time Factors
chemical_list: D017607:Aluminum Compounds; D002712:Chlorides; D019344:Lactic Acid; D000077410:Aluminum Chloride; D017693:Sodium Bicarbonate