Impact of Observation Duration in Action Observation Therapy: Manual Dexterity, Mirror Neuron System Activity, and Subjective Psychomotor Effort in Healthy Adults

Background: /Objectives: Action Observation Therapy (AOT) has gained attention as a re-habilitation method for motor function recovery following nerve injury. Although the total observation time and daily session duration have been studied, the effective observation duration per trial remains unclear. This study examined the effect of different observation durations on manual dexterity, mirror neuron system activity, and subjective psychomo-tor effort in healthy adults. Methods: Twenty-four healthy right-handed adults partici-pated in this crossover study under four conditions: observing ball rotations with the dominant hand for one, two, or three minutes, or geometric patterns (control) for two minutes. The outcomes included maximum rotations and errors by both hands during a ball rotation task and interpersonal motor resonance (IMR), indicating mirror neuron sys-tem activity. These measures were compared before and after intervention. Subjective rat-ings of concentration, physical fatigue, and mental fatigue were assessed post-intervention. Results: Rotation performance significantly increased for the interven-tion hand after a 2-minute observation and showed a notable effect (p = .113, r = 0.48) for the non-intervention hand after a 3-minute observation compared to the control. The IMR was significantly greater during the 2-minute observation than in the control. Compared to the 1-minute observation, the 2-minute and 3-minute observations resulted in higher mental fatigue, and the 3-minute observation showed lower concentration levels. Conclu-sions: These findings indicate that observation duration has varying effects on manual dexterity and mirror neuron system activity, with optimal effects observed at specific time intervals while also highlighting the relationship between observational learning and psychomotor effort.