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The Effect of Stud Flexibility on Lower Limb Biomechanical Demands in Football-Specific Movements
Gabriele Azzolini1, Silvia Fantozzi1,2, Andrea Ferretti3
1Department of Electrical, Electronic, and Information Engineering "Guglielmo Marconi," University of Bologna, Bologna, Italy.
Background:
Stud design is critical in modulating impact forces between football boot and turf, yet most systems prioritize traction using rigid materials, largely neglecting the role of material flexibility in load attenuation. This study assessed the biomechanical effects of 2 novel flexible stud designs compared with a traditional rigid stud during football-specific cutting and landing tasks.
Hypothesis:
Replacing traditional rigid studs with more flexible alternatives would reduce the magnitude and increase the time-to-peak of key lower limb loading variables.
Study Design:
Crossover study design.
Level Of Evidence:
Level 3.
Methods:
Fourteen recreational male players performed a planned 90° cut, a 180° cut, and a single-leg drop-land-and-cut on dry 3G turf wearing the same boot with 3 different stud sets: rigid (STD), flexible (OPT), and more flexible (FLX). Data analysis included scalar comparisons (approach speed, stance time, loading rates) and full-waveform analysis: amplitude-phase registration on ground reaction forces (GRFs) only, along with statistical parametric mapping of GRFs, knee kinematics, and moments. Subjective perception was assessed using a visual analog scale.
Results:
Participants rated flexible studs higher for stability, comfort, and overall appreciation. Approach speed and stance time were invariant across conditions. In 180° cuts, loading rates were higher with STD than FLX in both vertical (+33.42%) and mediolateral directions (+36.91%). Amplitude-phase analysis showed significant temporal shift during early stance, with STD exhibiting a phase lead compared with FLX. In 90° cuts, the pattern was similar: higher mediolateral loading rate with STD versus FLX (+25.06%) and STD inducing earlier GRF onsets. Knee dynamics did not show evidence of change.
Conclusion:
Increasing stud flexibility affected the timing of early load uptake - delaying and flattening the initial GRF rise - while improving perceived stability/comfort and preserving perceived grip.
Clinical Relevance:
This exploratory study identifies stud flexibility as an actionable design lever to mitigate highly impulsive loading, providing a mechanism for attenuating lower-limb load exposures in early stance - a period highly relevant to noncontact anterior cruciate ligament injury risk, showing better subjective perception of comfort and stability and without degrading overall player performance.
