[Age characteristics of the normal human skeletal musculature--mathematical description of postnatal skeletal muscle growth].

The number of muscle fibres per mm2 is age dependent, and therefore briefly denoted as age specific number (Alterskennzahl AK). We determined the AKs for the age groups up to 25 years, separated after the sexes and for M. vastus lateralis et deltoideus. According to the trend of the original data the approximations have been carried out applying 4 functions of organismic growth in modified form, i.e. the Pütter (1920), Bertalanffy (1934), Richards (1959), Janoschek extended by Sager (1984) and Richards extended after Sager (1980). Curve fitting is reached by regression analysis and nonlinear regressions using the sums of the linear deviations as a criterion for the goodness of fit. Results including initial as well as final values are summarized in tables with the parameters of the calculation methods added. The AKs allow judging the degree of maturity in the skeletal musculature during childhood. Transposing of the equations for AK = W yields t as a function of the normally adjunctive age specific number. The difference against real age reveals to which degree the musculature is eventually underdeveloped. Concerning the interpretation the fact should be kept in mind that biological processes are involved. The relation of the fibre types too implies a characteristic age dependency. This statement and the fibre diameters gained from the same material allow a mutual control and an exact fixation in each case.