Background: Daily muscle activity is important for functional independence. This study examined muscle activity patterns during normal daily life and simulated daily tasks and compared muscle activity and energy consumption during active and passive transport tasks in older adults.
Methods: Nine volunteers (70 ± 6 years) were measured for quadriceps and hamstring muscle activity (EMG) during normal daily life, treadmill walking, and during passive and active transport tasks. EMG was normalized to that recorded during maximal voluntary contraction (MVC). Oxygen uptake (VO2) was measured during treadmill and transport tasks.
Results: During daily life the mean EMG amplitude was 5.9 ± 2.4 % of EMGMVC, activity time was 187 ± 43 min and the longest continuous inactivity periods were 20.9 ± 10.0 min. During stair ascend the peak EMG activity was 120 % of EMGMVC and the peak VO2 values were only about 70 % of VO2max. One kilometer walk consumed 3.5 times more energy than passive transport by bus, and using stairs consumed 11.7 times more energy than using an elevator.
Conclusions: In daily life, older adults use only a small fraction of muscle's maximal capacity and have long continuous inactivity periods. Negotiating stairs produce significant load to neuromuscular, but not to cardiovascular system, thus providing an effective strength training stimulus.
Keywords: Aging; Electromyography; Energy expenditure; Independent living; Physical activity.