The presented method of isometric muscle strength measurement is the first with which this measurement has been demonstrated to be reliable and valid in 51 functional muscle groups in healthy women and men with an age ranging from 20-82 years. Percentile curves (3(rd), 10(th), 25(th), 75(th), 90(th), 97(th) percentile) allow the comparison of an individual muscle strength to population based normative values. Thus it enables the observer to estimate whether a subject's muscle strength confirms to the norm. Follow-up measurements may help to assess treatment effects in patients.