Internal focus instruction increases psychological stress with conscious motor processing and deteriorates motor performance in dart throwing.

Internal focus attention strategies have been found to diminish motor performance. This study attempted to elucidate this finding using the constrained action hypothesis and the theory of reinvestment through exploring their underlying mechanisms. Sixty-one young participants completed a self-paced "dart throwing" motor task to examine the effects of internal focus instruction, compared with no focus instruction, on conscious motor processing (reinvestment), psychological stress, and motor performance. Participants threw darts with standardized internal focus and no focus instructions given before each trial block of dart throwing. Motor performance was indicated by the throw accuracy and throw time. Stress was measured using a galvanic skin response probe. An insight into real-time conscious motor processing (reinvestment) was provided by the electroencephalography coherence between T3 and Fz locations on the scalp. Results indicated that internal focus instruction could cause participants to have lower throw accuracy (p = 0.008), longer throw time (p = 0.001), higher stress (p = 0.001) and higher real-time conscious motor processing (reinvestment) (p = 0.001) than no focus instruction. The significant results imply that internal focus instruction should be avoided in the self-paced motor task learning due to its detrimental effects.