The average ATP yield produced by MM creatine kinase after 30 min in the presence of 20 mM or natural Mg2+ (*Mg) is shown. Bars represent the standard error on the mean. and samples were placed in a number of different uniform magnetic fields over this time period. These were the ambient field (0 mT), 50, 83, and 1,000 mT. No increase in ATP production due to the isotope was observed, nor was a magnetic field effect observed. There was a small (15%) but significant (ANOVA-2; p < 0.001; N = 5) decrease in the samples versus the samples.