Specific results of research on the effects of exposure to 60-Hz electric and magnetic fields have often been contradictory and difficult to replicate. The study reported here used quantitative exercise testing techniques to evaluate whether increases in metabolism, caused by moderate steady-state exercise prior to exposure to real or sham fields, would clarify potential field effects. The feasibility of the methods and procedures used was clearly established. The findings indicated that the physical recovery process following moderate steady-state exercise performed under no-exposure conditions, was the same in real and sham fields. Of the variables examined, only cardiac interbeat interval (IBI) was altered by 2 hr of field exposure. A statistically significant increase in IBI (equivalent to a 3 beat/min decrease in heart rate) was found when subjects were exposed to the real field after sitting quietly prior to exposure. The replicates the earlier research, in which IBI was increased following a longer period of field exposure. The results suggest that future studies should examine a broader range of the continuum of human arousal and physiological activation.