Slipping during side-step cutting: anticipatory effects and familiarization

Area of Science:

• Biomechanics
• Motor Control
• Sports Science

Background:

• Side-step cutting maneuvers are common in sports and involve complex lower limb coordination.
• Understanding how the nervous system prepares for potential instability is crucial for injury prevention and performance optimization.

Purpose of the Study:

• To investigate the influence of expected perturbations on lower limb electromyography (EMG), heel kinematics, and ground reaction forces during side-step cutting.
• To determine if anticipatory muscle activity changes in response to potential balance loss.

Main Methods:

• Eighteen healthy men performed 90° side-step cutting maneuvers under unperturbed (Base), perturbed (Pert), and catch trial (Catch) conditions.
• Measurements included center of mass velocity, heel acceleration, ground reaction forces, and surface EMG of lower limb and trunk muscles.
• EMG analysis focused on pre-initial contact, load acceptance, and propulsion phases, with calculation of hamstrings-quadriceps co-contraction ratios.

Main Results:

• No significant changes were observed in center of mass velocity, heel acceleration, or peak ground reaction forces across conditions.
• During load acceptance, tibialis anterior EMG increased, while quadriceps, gluteus, and rectus abdominis EMG decreased in perturbed and catch trials.
• Quadriceps EMG remained reduced during propulsion, leading to increased hamstrings-quadriceps co-contraction ratios in perturbed and catch conditions.

Conclusions:

• The expectation of perturbations modulates lower limb muscle activity during side-step cutting maneuvers.
• Anticipatory adjustments in muscle activation and co-contraction ratios appear to enhance joint stability and ensure task safety.
• These findings highlight the predictive capabilities of the motor system in managing potential instability.