This research conducts three experimental studies on twelve male subjects to explore the physical workload of different computer tasks. Each study measures muscle electromyography (EMG) of extensor carpiradialis, extensor digitorum, extensor carpiulnaris, and flexor digitorum superficial, and pressing force of index finger in subjects’ dominant hand. Experimental studies comprise tasks of mouse target-acquisition, keyboard typing and mouse clicking, and fatigue test on index finger during continuous key/button pressing. Experimental results show raised typing and clicking speed significantly increases muscle workloads. However, no significant effects of clicking number, double-clicking, and cursor travel-distance on root mean square EMGs (RMS EMGs) were found under subjects’ self-selected speeds. In comparing keyboard typing and mouse clicking, RMS EMG measured in multiple-finger operation