Influence of shoe torsional stiffness on foot and ankle biomechanics

Influence of Shoe Torsional Stiffness on Foot and Ankle Biomechanics in Tennis

Abstract

  • Study investigates shoe characteristics affecting ankle injuries and foot performance during tennis.

  • Focuses on torsional stiffness of shoes affecting running velocity, stance duration, ground reaction forces (GRF), and ankle biomechanics in forehand strokes.

  • Ten advanced male players participated in testing with different shoe stiffnesses using a motion capture system and force platform.

Key Findings

  • Performance Parameters:

    • Shoe torsional stiffness had no significant effect on running velocity, stance duration, or maximal values of GRF during forehand strokes.

    • Flexible shoes resulted in higher forefoot inversion angles compared to stiffer shoes.

  • Ankle Biomechanics:

    • For the defensive forehand stroke (SRDF), the stiffest shoe led to significantly increased maximum ankle inversion angles, raising the risk of lateral sprains.

    • Results differ for the offensive jab run forehand (JROF), where no significant increase in inversion angles was noted.

Keywords

  • Performance, injury prevention, 3D analysis

Highlights

  • Shoe torsional stiffness does not affect various performance measures during tennis strokes.

  • Increased flexibility of shoes correlates with higher forefoot inversion angles during strokes.

  • The stiffest footwear poses a risk for ankle sprains in particular movements.

Introduction

  • Tennis involves swift start-stop movements and direction changes, making foot and ankle stability essential for performance.

  • High ground reaction forces during play contribute to ankle and foot injuries.

  • Injuries account for a significant percentage (12% ATP injuries; 21% NCAA injuries) of athlete injuries.

Factors Influencing Ankle Injuries

  • Various factors including ground surface, fatigue, physical condition, and shoe characteristics contribute to injury risk.

  • Lateral stability and torsional stiffness are critical characteristics for reducing injury risk in tennis shoes.

Literature Contradiction

  • Different studies report conflicting results about the impact of shoe torsional stiffness on injury risks:

    • Some studies indicate greater stiffness can increase injury risk, while others report benefits of stiffer footwear during certain movements.

Hypothesis

  • The study hypothesizes:

    • High torsional stiffness will not affect GRF, stance duration, or running velocity.

    • Increasing stiffness will decrease maximum ankle inversion angle and torque.

Materials and Methods

  • Participants:

    • 10 right-handed advanced male players participated, all healthy and injury-free.

    • Players performed specific tennis movements under predefined conditions.

  • Movements:

    • Shuttle run defensive forehand (SRDF) and lateral jab run offensive forehand (JROF) at maximum effort.

    • Use of a force platform (AMTI) to capture GRF; a Vicon motion capture system recorded 3D movement trajectories.

  • Shoe Testing:

    • Four pairs of shoes tested, varying in torsional stiffness: high flexible, flexible, stiff, high stiff.

    • Stiffness quantified using torque measurement methods.

    • Retro-reflective markers placed on anatomical landmarks for accurate motion assessment.

Results

Stance Time and GRF Peaks

  • Findings:

    • Stance duration, running velocity, and GRF peaks were not significantly affected by shoe stiffness in both SRDF and JROF movements.

Ankle and Forefoot Angles

  • Key Insights:

    • Significant effects of shoe stiffness on maximum inversion angles noted, especially in SRDF.

    • Flexible shoes prompted a higher maximum angle of forefoot inversion.

    • For JROF, angles showed moderate differences linked to shoe conditions.

Ankle Velocities and Torques

  • Ankle Velocity:

    • No significant effect on maximal velocity of ankle inversion for JROF; a marginal effect for SRDF noted.

  • Torque Observations:

    • Notable increase in ankle plantar flexion torque for flexible shoes compared to stiff options was significant.

Discussion

  • The study supports the understanding that stiffer shoes may induce greater peak ankle inversion and associated risk of sprains during dynamic tennis movements like SRDF.

  • Contradicts previous assertions that more rigid shoes consistently enhance performance without risk, indicating the need for optimal flexibility in footwear.

Recommendations

  • Tennis players, especially those involved in defensive plays, should consider shoes with lower torsional stiffness to mitigate injury risks, particularly during lateral movements.

Limitations

  • Study had limitations including small sample size; required a broader participant demographic to assess the varied effects of shoe stiffness.

Conclusions

  • No effect of shoe torsional stiffness on performance measures; significant influence on forefoot inversion noted.

  • Higher ankle inversion risk linked to stiffer shoes during specific movements.

  • Future research should include comfort assessments and follow injury patterns concerning shoe stiffness.