Visual feedback and motor control in swimming and walking

Introduction. In swimming, sensory-perception is strictly related to the so called “feel of the water” and to the ability in reducing the drag forces. Anyway the visual feedback, that has a basic role in the motor control and learning and that supports the swimmers in displacements along a straight direction when they swim in a lane, does not attend so easily in open water events. This study aimed to analyze the consequences of a visual deprivation both in walking exercise and in swimming. Methods 20 young swimmers, aged 8 to 11 years, participated to the study. After a familiarization to perform the trials at low to middle intensity, subjects underwent three tests both in visual feedback (VF) and in visual deprivation (VD) conditions: 25m front crawl and 25m backstroke in a double-wide lane set; 25m walking along a line in a gymnasium set. They were surveyed: i) stroke length (SL) and stroke rate in the first 10m of the swim tests (i.e. until no deviations were detected); ii) amplitude (PA) and frequency of the path in the first 10m of the walking test; iii) velocity (v) in the first 10m; iv) deviations of displacements from the straight direction; v) limbs dominance, vi) side of breathing in the 25m crawl. Results SL and PA significantly lowered (p<0.05) in VD (SL crawl: 1.8±0.27 vs 0,97±0.26, m/stroke; SL backstroke: 1.41±0.37 vs 1.16±0.25, m/stroke; PA: 1.16±0.19 vs 0.76±0.17, m; VF vs VD, respectively). In VD the velocities also decreased (Crawl: from 0.87±0.09 to 0.76±0.22, m/s; Backstroke: from 0.87±0.17 to 0.75±0.16, m/s; Walking: from 0.93±0.21 to 0.70±0.19, m/s; VF vs VD, respectively). Furthermore, subjects showed significant correlations between the side of the deviation and: 1) the side of breathing in the 25m crawl (p<0.01); 2) the lower limb dominance (p<0.01). Discussion There is evidence that visual deprivation significantly decreased the velocity of the displacements, both in swimming and in walking. The main effect of this deceleration is that the amplitude of SL and PA (i.e. the cinematic variables most related to the motor control and to the technical skills management) shortened. Visual deprivation probably induced subjects to displace more carefully, dropping the intensity of the actions in both the environments. The correlations between the side of the deviations and either the side of breathing in the 25m crawl and the lower limb dominance show that symmetry of the actions highly affects the spatial guidance. It can be concluded that in young swimmers, even in a simple task such as displacing at low to middle velocity for short distance, visual deprivation significantly modifies the output of the movements. References Novàk, J. (1982). Swimming direction and visual control. V Congress in Biomechanics and medicine in swimming (Amsterdam, Netherlands). Champaign, IL: Human Kinetics, 345-347.