Pressure algometry over normal muscles. Standard values, validity and reproducibility of pressure threshold.

Pressure threshold is the minimal pressure (force) which induces pain. The pressure threshold meter (PTM) is a force gauge with a rubber disc of 1 cm2 surface. The instrument has been proven to be useful in clinical practice for quantification of deep muscle tenderness. Trigger points, fibrositis, myalgic spots, activity of arthritis as well as assessment of sensitivity to pain can be diagnosed by PTM. This study therefore established standards for pressure threshold as well as the reproducibility and validity of measurement in 24 male and 26 female normal volunteers at 9 sites. Muscles frequently afflicted by trigger points were examined. The deltoid was chosen as a reference since it is rarely a site for trigger points. Comparison of corresponding muscles on opposite sides failed to demonstrate significant differences (except for 1 muscle in females). These identical results obtained over muscles of opposite sides proved the excellent reproducibility and validity of pressure threshold measurement. Results serve as a reference for clinical diagnosis of abnormal tenderness and for documentation of treatment results. The sensitivity of individual muscles varies. Therefore the results presented should be kept in mind when diagnosis of pathological tenderness by palpation is attempted.