Virtual Aging – Implementation of Age-Related Human Performance Factors in Ergonomic Vehicle Design Using the Digital Human Model RAMSIS

To date, there have been very few studies on the age dependence of maximal isometric muscle strength (MIMS) in healthy subjects aged 20-80 years, based upon measurements of a large number of functional muscle groups (FMGs). Using a hand-held pull gauge it is possible to measure MIMS of nearly every FMG. The objectives of this study were to obtain normative values for MIMS, to evaluate differences in MIMS in relation to gender and body side and to compare the age dependence of muscle strength between women and men. In a convenience sample of 290 healthy women (aged 20-82 years) and 253 men (aged 21-79 years), MIMS of 51 FMGs was measured. For each FMG the age dependence of MIMS was depicted, side and gender specific, as percentile curves and was analysed using linear quantile regression analysis. MIMS was found to be significantly higher in men than in women and higher on the right than on the left side. A biphasic model with linear equations for strength medians was derived for each gender. The age at transition from phase 1 to phase 2 was 55 years (SD 8) for women and 49 years (SD 13) for men. During phase 1, MIMS did not decrease significantly. During phase 2, MIMS decreased in all FMGs in both genders with a steeper slope in women (-0.92) than in men (-0.63). The age dependence of MIMS differed significantly between women and men. The present study gives gender-specific equations which enable one to calculate normative values for MIMS, as measured with a pull gauge, based upon age. These normative values will allow an objective assessment of patients with diminished muscle strength as, for example, in myositis, rheumatoid arthritis and nerve root compression syndromes or in the elderly.