Fig. 3. (A) Normalized RMS values of the EMG signal for quadriceps femoris (vastus lateralis, vastus medialis and rectus femoris) and (B) knee joint moment during isometric maximal voluntary knee extension contraction at 11 different joint angle configurations for the examined groups. Values are means ± S.D. RMS values for each subject were normalised to the highest RMS value measured over all joint angle configurations. O, older adults; Y, young adults. Asterisks indicate statistically significant differences between older and young adults: *P<0.05, **P<0.01, ***P<0.001; there was no age-by-running activity interaction for the analysed parameters (P>0.05).