Abstract
Background: Arch support has the effect of maintaining arch and correcting alignment, and it is broadly used for the prevention of sports impediment and treatment of athletes with lowered MLA and foot problems. The fact that the morphological change of MLA damages balance sense and postural control, it was reported that the insole supporting the arch of MLA improved postural balance. There are several studies regarding the effects of arch support; however, its effects on landing control have not been clarified. Therefore, in our research, we discussed the effect of MLA support for landing control, using lower limb dynamic alignment and the moment during landing as indexes. Methods: This study measured the landing motion to be evaluated was to jump from a platform with a height of 30 cm by taking-off with a single foot, and landing on a single foot on a floor reaction force gauge placed ahead and stay still for three seconds for the subjects were 13 healthy females. A soft 6 mm Boron sheet cut in the size of 9 × 3.5 cm, applied with double-sided tape (MLA pad) was used for arch support (hereafter referred to as “pad”). For the lower limb evaluation, an 8-camera with a three-dimensional behavioral analyzer (CORTEX, NAC product, sampling frequency: 120 Hz) and a floor reaction force gauge (AMTI product, sampling frequency: 1000 Hz) were used. Ten successful jump-landing tests for each limb were used for further analyses using Visual 3D software (Cmotion Inc., Kingston, Canada). Analysis objects were knee joint bending angle and valgus angle during landing; knee joint maximum bending angle; bending knee joint valgus angle, hip joint bending angle, adduction angle, ankle joint plantar flexion angle, varus angle at the time of knee joint maximum bending angle; and each joint moment. For statistical processing, the average value of three trials out of five trials was regarded as a representative value. Results: Regarding joint angles, significant differences were observed in maximum knee joint bending angle, knee joint bending angle during maximum valgus knee joint and ankle joint varus angle during knee joint maximum bending angle between before and after intervention. No significant differences were observed in other joint angles. Regarding joint moments, no significant difference was observed in each joint moment before and after the intervention. Significance: The decrease of knee joint valgus angle during landing by the use of MLA pad suggests the possibility of decreasing the risk of ACL injury. As the incidence of ACL injury in females is higher than that of males, and the evaluation for females had proceeded, it can be useful information for the prevention of ACL injury.
Highlights
It is known that the landing motion in sports is a motion by which athletes are injured [1] [2], and the injuries during landing account for 80% of the non-contact type injuries of the anterior cruciate ligament (ACL)
Regarding joint angles, significant differences were observed in maximum knee joint bending angle, knee joint bending angle during maximum valgus knee joint and ankle joint varus angle during knee joint maximum bending angle between before and after intervention
Knee joint and hip joint angle: + = flexion, − = extension, + = varus, − = valgus, + = abduction, − = adduction, ankle joint angle: + = dorsiflexion, − = plantarflexion, + = inversion, − = eversion, + = abduction (Data are expressed as mean ± standard deviation. *Significant effect, p < 0.05). It was discussed what effects the intervention of using an medial longitudinal arch (MLA) pad extended to the lower-limb joint angle and lower-limb joint moment during single-leg jump-landing
Summary
It is known that the landing motion in sports is a motion by which athletes are injured [1] [2], and the injuries during landing account for 80% of the non-contact type injuries of the anterior cruciate ligament (ACL). The knee-in position during landing, which is the site prone to injury, is regarded as a typical example, and it is considered that the stress on the knee valgus caused by external rotation of hip joint eventually leads to stretching stress of ACL and resulting in injury During loading postures such as standing and landing, the medial longitudinal arch (MLA) extends its effect on the dynamic knee valgus [3]. MLA is a shape-changeable arch structure [4] and the changes in its height exert influence on the plantar pressure distribution [5], affecting the absorption of the power from the land surface [6], muscular activity [7], stability [8] and loading posture [9] It affects foot pronation [10], internal rotation of the tibia [11] and the actions of knee varus and valgus, so that when MLA decreases, foot pronates and concomitantly knee joint valgus movement occurs and causes ACL injury. Analysis objects were knee joint bending angle and valgus angle during landing; knee joint maximum bending angle; bending knee joint valgus angle, hip joint bending angle, adduction angle, ankle joint plantar flexion angle, varus angle at the time of knee joint maximum bending angle; and each joint mo-
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