Table 1.
Inflection points, myoglobin desaturation, critical Po2, and ATP production during ischemia in resting muscle
| Variable | Mean | SD | Range | 95% CI |
|---|---|---|---|---|
| PCr inflection point, s | 276 | 102 | 184–428 | 195, 357 |
| pH inflection point, s | 305 | 86 | 219–422 | 229, 380 |
| Myoglobin desaturation at PCr inflection point, % | 87.6 | 6.0 | 85.3–93.8 | 81, 94 |
| Critical Po2, Torr | 0.35 | 0.20 | 0.16–0.72 | 0.14, 0.56 |
| ATP production from PCr, mM/s | 0.013 | 0.003 | 0.011–0.018 | 0.010, 0.015 |
The phosphocreatine (PCr) and pH inflection points were determined from iterative bilinear fits for each subject. Critical Po2, defined here as the Po2 at which oxidative phosphorylation became compromised, was calculated from the relative desaturation of myoglobin (%max) observed at the PCr inflection point. ATP production in the resting tibialis anterior was calculated based on the 1:1 stoichiometry of PCr and ATP in the creatine kinase reaction. CI, confidence interval. See text for details.