Effects of experience in a dynamic environment on postural control

Background: Surfing is a balance-reliant, open skill performed in a dynamic environment rich in visual, somatosensory and vestibular information. Objective: To evaluate adaptations to the postural control system by surfing experience. Methods: Postural control was assessed in an upright bipedal stance in 60 male volunteers (21 elite surfers, 20 intermediate level surfers, and 19 controls) using various closed-stance positions. Six tasks were performed with two trials including a cognitive task, in the following order: eyes open, head in a neutral position (EO1); eyes closed, head in a neutral position (EC); eyes closed, head back (ECHB); eyes open, head in a neutral position, cognitive task 1 (EOC1); eyes open head in a neutral position, cognitive task 2 (EOC2); eyes open head in a neutral position (EO2). Dependent variables were area of 95th centile ellipse (AoE) and sway path length (SPL). Results: All participants showed systematic increases in SPL and AoE in EC and ECHB trials. Expert surfers displayed significantly (p < 0.05) increased SPL but not AoE when sharing attention with both concurrent mental tasks compared with controls. Controls showed a slight, non-significant change in postural control (reduced SPL and AoE) when attending to concurrent mental tasks. Conclusions: The findings indicate that standard postural sway indices are not able to elucidate whether expertise in surfing facilitates adaptations to the postural control system. However, concurrent mental task findings illustrate that systematic differences in balance abilities between expert surfers and controls may exist.