Age and Sex Differences in the Levels of Muscular Activities during Daily Physical Actions

The present study aimed to clarify age and gender differences in the electromyographic (EMG) activity levels of lower limb muscles during daily physical actions. Forty young and 22 elderly individuals performed five physical actions, i.e. normal walking, ascending and descending stairs, standing up from and sitting onto a chair, and a calf raise exercise. The surface electromyograms (EMGs) during these actions were recorded from the vastus medialis, rectus femoris, vastus latelalis, lateral gastrocnemius, medial gastrocnemius, and soleus muscles using a portable EMG recording apparatus. For the prescribed actions, the mean activity levels of the quadriceps femoris (QF%EMG) and triceps surae (TS%EMG) muscles were quantified and expressed as the relative values (%EMG) to that during the maximal voluntary isometric contraction (MVC). The %EMG values of QF and TS significantly differed among actions, with significant influences of age and gender. The %EMG of each of QF and TS was negatively correlated to MVC torque relative to body weight, developed in knee extension and ankle plantar flexion, suggesting that the observed age and gender differences in %EMG could be partially attributed to those in torque generation capabilities. Thus, the present findings indicate that the individuals with lower maximal isometric joint torque per body weight demonstrate higher muscular activity levels during daily physical actions. For these populations, the daily physical actions examined here may be resistance exercises for improving the torque generation capability of lower limb muscles.