|Title of the paper:||The behavior of the medial longitudinal arch with ground reaction force during single leg drop jump|
|Authors:||Keiji Koyama1, Yutaro Kosugi1, Junichiro Yamauchi2,3|
|Institution:||1. Toin University of Yokohama, Kanagawa, JAPAN 2. Tokyo Metropolitan University, JAPAN|
|Department:||1. Sport Technology, 2. Graduate School of Human Health Sciences|
The medial longitudinal arch (MLA) of the foot serves a role in shock absorption and provides a forward propulsion during weight bearing activities. When encumbered with load, MLA lengthens and lowers, subsequently shorten and recoiling as the load is removed (Ker et al. 1987). We speculated that barefoot performance allows the foot arches to absorb shock and to strength on the muscles and tendons of the feet in contact phase during drop jump (Koyama and Yamauchi, 2018). However, there were no study of how MLA behave in foot contact phase, and how behavior of MLA is related to drop jump performance variables. The aim of this study was firstly to examine the behavior of MLA with ground reaction force during single leg drop jump, and secondly to examine whether the deformation of MLA related to performance variables during single leg drop jump.
Ten healthy men performed dominant single leg drop jump from both 10cm- (SLD10) and 45cm-height (SLD45) under barefoot. The ground reaction force (GRF) variables and the behavior of MLA were recorded by the force plate and by four high-speed video cameras, respectively. Force-time curve of GRF was represented as the relative range between initial contact of landing and take-off. The landing and the push-off phases were defined respectively from the initial contact on the force plate to the maximum dorsiflexion at the ankle joint and from the maximum dorsiflexion at the ankle joint to take off. The maximum vertical ground reaction force (MGRF), contact time and jump height (JH) were analyzed and MGRF was normalized body weight. Three retroreflective markers were placed on the navicular tuberosity, the medial border of the first metatarsal head and the medial tubercle of the calcaneus (Kelly et al. 2015). MLA angle was analyzed from three-dimensional coordinate values of these retroreflective markers. The amount of change in angle of MLA (?MLA) was calculated in landing and push-off phases.
JH and MGRF in SLD45 (JH: 13.30 ± 1.97 cm, MGRF: 3.90 ± 0.61 BW) were lower and larger compared with SLD10 (JH: 14.49 ± 2.39 cm, MGRF: 2.85 ± 0.49 BW), respectively. ?MLA at both landing and push-off phases were significantly greater in SLD45 (landing: 17.47 ± 3.08 deg, push-off: 16.80 ± 3.85 deg) compared with SLD10 (landing: 14.02 ± 2.13 deg, push-off: 15.71 ± 3.06 deg). MLA angle was increased in landing phase and decreased in push-off phase both SLD45 and SLD10. ?MLA at both landing and push-off phases were significantly correlated with JH (landing: n = 20, r = -0.477, p < 0.05, push-off: n = 20, r = -0.536, p < 0.05).
This study demonstrated that MLA was served a role in shock absorption and force generation during single leg drop jump. The deformation of MLA was related to jump height in single legged drop jump.
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Koyama K and Yamauchi J. (2018). J Biomech. 47-53.