EFFECTS OF PRIOR EXERCISE OR AMMONIUM-CHLORIDE INGESTION ON MUSCULAR STRENGTH AND ENDURANCE

Previous studies linked muscular fatigue with a decrease in blood pH. This study investigated if the means of altering pH affected the exten t of muscular fatigue. Drug-induced and exercise-induced acidosis were compared to test the hypothesis that exercise-induced acidosis impair s subsequent muscular performance more than chemically induced acidosi s. In eight male subjects acidosis was induced by ingesting 0.3 g.kg-1 ammonium chloride (AC) for one trial, by upper body exercise (UBE) fo r another trial, and after placebo (PL) treatment. They then completed a performance test (PT) of 50 maximal, bilateral isokinetic knee exte nsions. Whole blood pH before (pH(pre)) and after (pH(post)) the PT wa s 7.412, 7.264, and 7.261 for PL, UBE, and AC, respectively; both AC a nd UBE decreased pH similarly compared with PL. Peak torque and total work during the PT were similar for PL and AC, and were significantly greater than after UBE. Six subjects performed a fourth trial after co mbined AC and UBE treatments causing a pH(pre) of 7.081, but there was no greater performance impairment than that caused by UBE alone. The results dissociate the extent of the impairment from the magnitude of the disruption in blood pH.