Influence of footwear typically worn during field hockey participation, velocity and surfaces on tibial accelerations during locomotion

INTRODUCTION
Field Hockey is a popular sport played predominantly on artificial sports surfaces requiring sustained periods of locomotion at various velocities. During human locomotion the body is exposed musculoskeletal transient shocks that have been linked to various injuries (Aguinaldo and Mahar 2003). The magnitude of the impact shocks have been reported as being affected by the velocity of locomotion, movement strategies, the surface and the footwear worn (Clarke et al 1983). Therefore choosing appropriate conditions should reduce the levels of impact shock experienced reducing the risk of injury.
PURPOSE OF THE STUDY
The Purpose of this study was to investigate the influence of footwear, surface and speed on the magnitude of tibial shock.

METHODS
Nine male participants, (Age 21 + 1.69, Height 175.75 + 6.56 and Mass 78.13 + 12.11) volunteered to take part in this study. All participants were injury free at the time of data collection and completed an informed consent form. A tri-axial accelerometer (Biometrics ACL300) sampling at 1000Hz was mounted to a lightweight carbon-fibre plate via a securely glued lightweight bolt and thread. The accelerometer signal was recorded by a Biometrics DataLog system (Biometrics Ltd, Gwent, UK). The accelerometer signal was filtered at 60Hz using a Butterworth 4th order zero-lag low-pass filter. The concrete surface at the side of the pitch was typical of the sort of surface on which field hockey participants would warm up prior to matches. Participants were required to run in each of the footwear at 5m.s-1 (running) and 3.3m.s-1 (jogging).
RESULTS
Significant differences were observed between running and jogging for the different surfaces. Significant differences in the tibial axial peak were also reported when comparing the effects of surface during running, however during jogging significant differences were not found. Significant differences between mean tibial acceleration values in the Saucony Running, Umbro Soccer Astroturf, and Gryphon Venom, when compared to Umbro Soccer Moulded during running on synthetic surfaces. No other significant differences were found across the population of participants between the shoes for the 3 other surface and velocity conditions (running on synthetic surface, jogging on concrete, running on concrete).

DISCUSSION
It appears that footwear only has a measureable effect across the population of participants, during running at a higher speed (5m.s-1). The significant differences recorded were all cases where the Umbro Moulded shoes exposed the athlete to higher tibial axial accelerations than the other shoe conditions. This occurred only in the running group on the synthetic sports surface This may have been replicated on the concrete but it was considered not safe for participants to run in Umbro Moulded shoes on a concrete surface. Furthermore, the same footwear (Umbro Moulded) as in the previous chapter was highlighted as exposing the population to a significant increase in detrimental kinetic factors. The results of this research suggest that participating in high velocity activities on hard concrete surfaces, exposes the musculoskeletal to significantly larger impact shocks. This information can be used by coaches to select suitable activities with the surfaces available to them.

This investigation also identified that during running on synthetic sports surfaces, moulded soccer shoes with hard deep cleats expose the body to larger impact shocks than shoes designed for running and synthetic sports surfaces. Therefore these types of shoes should not be used in field hockey participation on such surfaces. Significant differences in the magnitude of tibial shock between similar footwear designs used by field hockey participants were also identified using the methodologies in this study. The evidence from individual participant provides some assistance for footwear selection. However, the findings of this study demonstrated that shoes can reduce impact shock for one individual while increasing it for another. Therefore, for a participant to be confident of making the correct choice of footwear in relation to exposure to tibial shock, the footwear needs to be tested on an individual basis.