Motor unit activity during stereotyped finger tasks and computer mouse work

Motor unit (MU) activity pattern was examined in the right-hand extensor di gitorum communis muscle (EDC) during standardised finger movements simulati ng actual computer mouse tasks. Intramuscular recordings were performed wit h a quadripolar needle electrode. Nine women performed four lifts of their right-hand index finger, middle finger or both as well as a number of doubl e clicks. Additionally, the subjects performed contra lateral activity with their left-hand fingers and for three subjects recordings were also obtain ed during an interview with no physical activity. Besides the expected clos e coupling of MU activity with finger movement, activity was observed in th ree different situations with no physical requirements. Attention related a ctivity was found before or after performance of the finger movement task, contra lateral activity in right EDC during left-hand finger tasks, and act ivity during mental activity without any finger movements involved. A relat ively large number of doublet occurrences suggest they are a natural part o f the activation pattern during performance of the rapid finger movement re quired to perform an efficient double click on the computer mouse. (C) 2001 Elsevier Science Ltd. All rights reserved.