Relationship between Tilt Sensation Ability and Lower Limb Injuries in Junior Athletes.

The purpose of this study was to devise a tilt sensation measurement method to evaluate ankle proprioception and to examine its reliability. It was also used to determine the relationship among tilt sensation abilities, physical development, and lower limb injuries in junior athletes. In this study, a step platform created tilt angles. Participants with eye masks answered "yes" or "no" to sensing a tilt, evaluated over nine or seven trials. Experiment 1 involved 22 university students (20.6 ± 0.9 years). The minimum angle at which a tilt could be sensed while standing on both feet was determined, and measurements were taken again to examine reliability. Experiment 2 involved 40 junior athletes (12.3 ± 2.0 years), where the minimum angle for tilt sensation was obtained, and medical checks were conducted to assess injuries in the knee, lower leg, and foot. Reliability studies showed a moderately significant correlation between the first and second sessions (r = 0.504, p = 0.017), suggesting the reliability of the experimental method. The proportion capable of sensing a tilt of 1.1° and 1.6° was significantly higher in junior high school students than in elementary school students (1.1°; χ2 = 8.839, p = 0.003. 1.6°; χ2 = 4.038, p = 0.044). The group unable to sense a tilt of 1.6° and 2.1° had a significantly higher positive rate of knee injuries compared to the sensed group among junior high school students (1.6°; χ2 = 4.622, p = 0.032. 2.1°; χ2 = 4.622, p = 0.032). Our findings suggested that a reduced tilt sensation ability was associated with knee injuries in junior high school students. Utilizing our devised tilt sensation assessment could play a crucial role in preventing and detecting early injuries in junior high school students.

Dissociation of perception and motor execution of lower limb in multi-directional movements.

Estimating the action capability is vital for humans to move their bodies successfully. Researchers have proposed reachability as an overestimation of motor abilities by judging unreachable distances as reachable. The existing literature has mainly investigated the sagittal direction, but multi-directional reachability is unexplored. This study examined the relationship between perception and motor using the reaching of the lower limbs in multiple directions. We asked 16 adults to reach targets projected onto the floor at 21 locations (seven directions and three distances) to estimate the reaching time. We found that the reaching time slowed as the direction increased toward the contralateral side, but the subjective reaching time did not change with direction. Multiple regression analysis showed that the subjective reaching time could be calculated accurately, mainly using the duration from the toe leaving the ground to movement completion. These results suggest that changes in direction may not be perceived precisely by the motor system of the lower limbs and that the subjective reaching time was strongly affected by the time after the toe left the ground. Our findings provide novel insights into the relationship between motor and perception in multiple directions, which may provide a new strategy for the maximal performance of lower-limb movement.

Direction and distance dependency of reaching movements of lower limb.

Efficient body movement is required in our daily lives, as it facilitates responding to the external environment and producing movements in various directions and distances. While numerous studies have reported on goal-directed movements in the frontal direction during gait initiation, there is limited research on the efficient movement of the lower limbs in multiple directions and distances. Therefore, we aimed to examine changes in the kinematics of lower-limb reaching movements to determine skilled motor ability in terms of direction and distance. Sixteen adults (10 male participants) were requested to reach targets projected on the floor in seven directions and at three distances for a total of 21 points. The reaching time slowed down for the contralateral side (right foot to left-sided target) and was caused by a slower start of the toe movement. To identify the cause of this delay, we analyzed the onset of movement at each joint and found that movement to the contralateral side starts from the hip, followed by the knee, and subsequently the toe. The time-to-peak velocity was also calculated, and the motion required to reach the target in the shortest time varied depending on direction and distance. These results suggested that movement kinematics vary with direction and distance, resulting in a slower reaching time on the contralateral side. The results of our study hold promise for potential applications in sports and rehabilitation.