The effect of citrate loading on exercise performance, acid-base balance and metabolism.
Nine subjects (VO2max 65 +/- 2 ml.kg-1.min-1, mean +/- SEM) were studied on two occasions following ingestion of 500 ml solution containing either sodium citrate (C, 0.300 g.kg-1 body mass) or a sodium chloride placebo (P, 0.045 g.kg-1 body mass). Exercise began 60 min later and consisted of cycle ergometer exercise performed continuously for 20 min each at power outputs corresponding to 33% and 66% VO2max, followed by exercise to exhaustion at 95% VO2max. Pre-exercise arterialized-venous [H+] was lower in C (36.2 +/- 0.5 nmol.l-1; pH 7.44) than P (39.4 +/- 0.4 nmol.l-1; pH 7.40); the plasma [H+] remained lower and [HCO3-] remained higher in C than P throughout exercise and recovery. Exercise time to exhaustion at 95% VO2max was similar in C (310 +/- 69 s) and P (313 +/- 74 s). Cardiorespiratory variables (ventilation, VO2, VCO2, heart rate) measured during exercise were similar in the two conditions. The plasma [citrate] was higher in C at rest (C, 195 +/- 19 mumol.l-1; P, 81 +/- 7 mumol.l-1) and throughout exercise and recovery. The plasma [lactate] and [free fatty acid] were not affected by citrate loading but the plasma [glycerol] was lower during exercise in C than P. In conclusion, sodium citrate ingestion had an alkalinizing effect in the plasma but did not improve endurance time during exercise at 95% VO2max. Furthermore, citrate loading may have prevented the stimulation of lipolysis normally observed with exercise and prevented the stimulation of glycolysis in muscle normally observed in bicarbonate-induced alkalosis.
Department of Kinesiology, University of Waterloo, Ontario, Canada.
J M
JM
Kowalchuk
S A
SA
Maltais
K
K
Yamaji
R L
RL
Hughson
D000136:Acid-Base Equilibrium / Q000187:drug effects*; D000328:Adult; D001784:Blood Gas Analysis; D001786:Blood Glucose / Q000032:analysis; D002951:Citrates / Q000097:blood / Q000494:pharmacology*; D019343:Citric Acid; D004526:Efficiency; D015444:Exercise; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005990:Glycerol / Q000097:blood; D006339:Heart Rate; D006400:Hematocrit; D006454:Hemoglobins / Q000032:analysis; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007773:Lactates / Q000097:blood; D010101:Oxygen Consumption; D013997:Time Factors
D001786:Blood Glucose; D002951:Citrates; D005230:Fatty Acids, Nonesterified; D006454:Hemoglobins; D007773:Lactates; D019343:Citric Acid; D005990:Glycerol