Acidosis, but Not Alkalosis, Affects Anaerobic Metabolism and Performance in a 4-km Time Trial. Issue 9 (September 2017)

• Record Type: Journal Article
• Authors: CORREIA-OLIVEIRA, CARLOS RAFAELL; LOPES-SILVA, JOÃO PAULO; BERTUZZI, ROMULO; MCCONELL, GLENN K.; BISHOP, DAVID JOHN; LIMA-SILVA, ADRIANO EDUARDO; KISS, MARIA AUGUSTA PEDUTI DAL'MOLIN
• Is Part Of: Medicine and science in sports and exercise. Volume 49:Issue 9(2017)
• Publication Date: 2017-09
• Subjects: AMMONIUM CHLORIDE -- SODIUM BICARBONATE -- ANAEROBIC WORK CAPACITY -- PERFORMANCE -- GASTROINTESTINAL DISCOMFORT; Sports medicine -- Periodicals; Exercise -- Physiological aspects -- Periodicals; Exercise -- Health aspects -- Periodicals; 612.044
• DOI: 10.1249/MSS.0000000000001295
• Languages: English
• ISSNs: 0195-9131

Abstract

ABSTRACT: Purpose: 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). Methods: Eleven recreationally trained cyclists (V˙O2peak 54.1 ± 9.3 mL·kg −1 ·min −1 ) performed a 4-km TT 100 min after ingesting in a double-blind matter 0.15 g·kg −1 of body mass of ammonium chloride (NH4 Cl, acidosis), 0.3 g·kg −1 of sodium bicarbonate (NaHCO3, alkalosis), or 0.15 g·kg −1 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. Results: Compared with placebo (pH 7.37 ± 0.02, [HCO3 − ]: 27.5 ± 2.6 mmol·L −1 ), the NaHCO3 ingestion resulted in a preexercise blood alkalosis (pH +0.06 ± 0.04, [HCO3 − ]: +4.4 ± 2.0 mmol·L −1, P < 0.05), whereas NH4 Cl resulted in a blood acidosis (pH −0.05 ± 0.03, [HCO3 − ]: −4.8 ± 2.1 mmol·L −1, P < 0.05). Anaerobic energy expenditure rate and PO were reduced throughout the trial in NH4 Cl 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 NH4 Cl 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. Conclusion: Preexercise acidosis, but not alkalosis, affects anaerobic metabolism and PO during a 4-km cycling TT.