Attentional focusing instructions influence force production and muscular activity during isokinetic elbow flexions

Appropriate verbal instruction is critical to effective guidance of movements. Internal (movement focus) and external (outcome focus) attentional focusing instructions have been shown to influence movement kinetics and muscular activity; this study investigated their effects during a force production task. Twenty-five participants (mean age of 22.72 +/- 1.88 years) completed 10 repetitions of single-arm elbow flexions on an isokinetic dynamometer while electromyographical activity of the biceps brachii and net joint elbow flexor torque were measured. Three trials were completed: a control trial to attain maximum voluntary contraction (MVC) data, followed by counterbalanced trials internal and external attentional focus conditions. The external focus exhibited a significantly (p < 0.05) higher peak net joint torque (102.10 +/- 2.42%MVC) than the internal condition (95.33 +/- 2.08%MVC) and also a greater integral of the torque-time curve (99.90 +/- 2.91%MVC) than the internal condition (93.80 +/- 2.71%MVC). In addition, the external focus resulted in lower peak electromyography (134.43 +/- 16.83%MVC) response when compared with the internal focus condition (155.23 +/- 22.54%MVC) as well as lower mean integrated electromyography (127.55 +/- 12.24%MVC) than the internal condition (154.99 +/- 19.44%MVC). Results indicate that an external attentional focus results in significantly greater force production and lower muscular activity during isokinetic elbow flexions when compared with an internal focus. When instructing clients during maximal force production tasks, practitioners should tailor their instructions to emphasize an external focus of attention. Specifically, attention should be directed onto the movement of the object being moved and away from the specific bodily movements involved in the action.