A Pilot Study of the Effect of Outsole Hardness on Lower Limb Kinematics and Kinetics during Soccer Related Movements

Abstract

The purpose of this study was to investigate the effect of different outsole hardness of turf cleats shoes on the lower limb kinematics and kinetics of soccer players playing on artificial turf. The participants were required to complete tasks of straight running and 45° left sidestep cutting movements, respectively, at the speed of 4.5 ± 0.2 m/s on artificial turf. They were asked to randomly select turf cleats shoes with a soft outsole (SO), medium hardness outsole (MO) and hard outsole (HO). During the stance phase of straight running, peak pressure and force-time integral in medial forefoot (MFF) of players wearing cleats shoes with MO were significantly higher than those wearing cleats shoes with SO. During the stance phase of a 45° cutting maneuver, players wearing cleats shoes with SO showed significantly higher peak knee flexion and abduction angles than the HO group. Players wearing cleats shoes with SO also showed higher ankle dorsiflexion and inversion angles compared with those wearing cleats shoes with HO. The vertical average loading rate (VALR) as well as peak pressure and force-time integral in the heel (H) and lateral forefoot (LFF) regions of players wearing cleats shoes with HO were significantly higher than those wearing shoes with SO. On the contrary, peak pressure and force-time integral of players wearing shoes with SO were significantly higher than those wearing shoes with HO in MFF. A higher vertical loading rate and plantar pressure of some areas may increase the potential risk of metatarsal stress fractures and plantar fasciitis. Therefore, this finding about turf cleats shoes could give some theoretic support for the design of turf cleats shoes and material optimization in the future.

Keywords: injury; outsole hardness; performance; turf cleats shoes.

Figure 1

Anatomical areas of the plantar region

Figure 2

The design of the experimental protocol

Picture 1

A, B and C represent ankle, knee and hip angle curves in the stance phase of 45° cut, respectively

Picture 2

Vertical ground reaction force during the stance period of 45° cut when wearing SO turf shoes

Picture 3

Peak pressure and force-time integral of three pairs of turf shoes in straight running (a&b) and 45° cutting movement (c&d) *Significant difference between SO and MO turf shoes. p < 0.05; #Significant difference between SO and HO turf shoes. p < 0.05.