Abstract
Among the cognitive strategies that can facilitate motor performance in sport and physical practice, a prominent role is played by the direction of the focus of attention and the placebo effect. Consistent evidence converges in indicating that these two cognitive functions can influence the motor outcome, although no study up-to-now tried to study them together in the motor domain. In this explorative study, we combine for the first time these approaches, by applying a placebo procedure to increase force and by manipulating the focus of attention with explicit verbal instructions. Sixty healthy volunteers were asked to perform abduction movements with the index finger as strongly as possible against a piston and attention could be directed either toward the movements of the finger (internal focus, IF) or toward the movements of the piston (external focus, EF). Participants were randomized in 4 groups: two groups underwent a placebo procedure (Placebo-IF and Placebo-EF), in which an inert treatment was applied on the finger with verbal information on its positive effects on force; two groups underwent a control procedure (Control-IF and Control-EF), in which the same treatment was applied with overt information about its inefficacy. The placebo groups were conditioned about the effects of the treatment with a surreptitious amplification of a visual feedback signalling the level of force. During the whole procedure, we recorded actual force, subjective variables and electromyography from the hand muscles. The Placebo-IF group had higher force levels after the procedure than before, whereas the Placebo-EF group had a decrease of force. Electromyography showed that the Placebo-IF group increased the muscle units recruitment without changing the firing rate. These findings show for the first time that the placebo effect in motor performance can be influenced by the subject’s attentional focus, being enhanced with the internal focus of attention.
Highlights
Motor performance can be enhanced in athletes and non-athletes by mean of placebo procedures[1,2,3,4,5,6], in which inert treatments or substances are administered together with verbal information about their powerful effects on the motor outcome
Plenty of literature suggests that verbal instructions to focus attention away from the body movements lead to better motor performance as compared to verbal instructions to focus on the body movements[19,20]
The results of this study show for the first time that the placebo effect in the motor domain can be influenced by the direction of the focus of attention
Summary
Motor performance can be enhanced in athletes and non-athletes by mean of placebo procedures[1,2,3,4,5,6], in which inert treatments or substances are administered together with verbal information about their powerful effects on the motor outcome. Previous research in pain has shown that when participants receive verbal instructions to focus on the body part in which the effects of a treatment are expected, the placebo response is enhanced[18] This suggests that different verbal information can direct attention towards or away from the body and this has an impact on the placebo response. Plenty of literature suggests that verbal instructions to focus attention away from the body movements (the so-called, external focus of attention, EF) lead to better motor performance as compared to verbal instructions to focus on the body movements (internal focus of attention, IF)[19,20] This pattern seems to be associated to changes at the neuromuscular level, with a generally lower EMG activity and fewer co-contraction of agonist and antagonist muscles when the movements are executed with an external focus of attention[21,22]. The general assumption is that a more parsimonious pattern of muscular activation is indicative of more efficient and automatic movement execution that leads in turn to a good motor performance with less effort and fatigue[34]
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