Olfaction and muscle activity: an EMG pilot study.

The therapeutic significance of limbic system structures in general, and olfactory structures specifically, has been described by Fox, Ayres, Moore, and Farber in their professional presentations and publications. No data have yet been provided to substantiate claims of the effects of olfactory stimulation on muscle activity. Effects of olfactory stimulation on human muscle activity at rest were studied in seven normal children and seven normal adults. Upper trapezius, biceps brachii, rectus abdominis, and rectus femoris were monitored electromyographically for changes in muscle action potentials using peppermint oil and smelling salts in each of three positions--supine, seated quietly, and standing. Trapezius showed the greatest responsiveness in relation to other muscles. Using peppermint oil, only 18 out of 168 or 10.7 percent of the EMG recordings showed changes in muscle activity. Using smelling salts, only 21 out of 168 or 12.5 percent of the EMG recordings showed changes in muscle activity. Directional effects of peppermint oil could not be predicted, whereas stimulation with smelling salts, when effective, generally produced increased muscle activity. Children were more responsive to olfactory agents than were adults. Sex of subjects did not seem to effect the distribution of responses. When smelling salts was presented as an initial stimulus, subjects showed a greater responsiveness to all stimuli. The present data indicate that proposed effects of olfactory stimulation are more limited than was previously believed. Possible implications for clinical practice and suggestions for further study are presented.