Abstract
threshold (pHT) detected by eye (E), and by regression analysis on linear (L), semilog (SL) and log-log (LL) models. Threshold for inorganic phosphate-to-phosphocreatine ratio (PT) was also examined by three regresslon analysis. Flfteen males volunteered as subjects. They performed wrist flexion in a ramp protocol of 0.14W/min till exhaustion. Throughout the exercise, 31P-MRS was obtained continuously from wrist flexors. Intracellular pH and phosphate compound in the muscle tissue were monitored as minute-by-minute data. In E, three observers determined pHT subjectively as a work rate just before pH decrement. In three regression analysis, pHT was detected as an intersection of a pair of linear regression lines which was selected statistically or subjectively. pHT detected by four methods showed significant re-producibility between each other, although PT did not. These results provide one of the evidences of threshold behavior of change in pH, and a question of existence of PT in contrast to pHT.
