Immediate effect of attentional focus on muscle activity during knee extension and imagined knee extension using ultrasound doppler: Quasiexperimental research

Background: Attentional focus and motor imagery affect muscle activity. However, there are no studies that use visualization technique of ultrasound doppler to monitor muscle activity while focusing on the actual and imagined movement. Objective: To compare the effect of attentional focus on muscle activity during knee extension and determine knee extension using ultrasound doppler. Methods: Twenty-four participations, age ranged from 20 - 30 years old, were asked to perform three types of muscle contraction, including active knee extension, eccentric contraction of knee extensor, and isometric knee extension. In addition, all subjects were asked to perform three attentional focus, namely no attentional focus, internal focus, and external focus during perform each type of muscle contraction. Results: The muscle size was monitored while perform knee extension and imagined knee extension. The muscle size of knee extensor during actual knee extension was significantly greater than imagined knee extension in all type of muscle contraction. There were no statistically significant differences in knee extensor muscle size during actual movement among attentional conditions, whereas knee extensor muscle size while imagining knee extension with external focus was greater than internal focus and no attentional focus. Conclusion: Both actual and imagined movement could alter muscle size. Interestingly, attentional focus had effect on the alteration of muscle size only during perform imagined knee extension.