Effect of Limiting Ankle-Dorsiflexion Range of Motion on Lower Extremity Kinematics and Muscle-Activation Patterns During a Squat

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Elisabeth Macrum
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David Robert Bell
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Michelle Boling
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Michael Lewek
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Darin Padua
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Context:

Limitations in gastrocnemius/soleus flexibility that restrict ankle dorsiflexion during dynamic tasks have been reported in individuals with patellofemoral pain (PFP) and are theorized to play a role in its development.

Objective:

To determine the effect of restricted ankle-dorsiflexion range of motion (ROM) on lower extremity kinematics and muscle activity (EMG) during a squat. The authors hypothesized that restricted ankle-dorsiflexion ROM would alter knee kinematics and lower extremity EMG during a squat.

Design:

Cross-sectional.

Participants:

30 healthy, recreationally active individuals without a history of lower extremity injury.

Interventions:

Each participant performed 7 trials of a double-leg squat under 2 conditions: a nowedge condition (NW) with the foot flat on the floor and a wedge condition (W) with a 12° forefoot angle to simulate reduced plantar-flexor flexibility.

Main Outcome Measures:

3-dimensional hip and knee kinematics, medial knee displacement (MKD), and ankle-dorsiflexion angle. EMG of vastus medialis oblique (VMO), vastus lateralis (VL), lateral gastrocnemius (LG), and soleus (SOL). One-way repeated-measures ANOVAs were performed to determine differences between the W and NW conditions.

Results:

Compared with the NW condition, the wedge produced decreased peak knee flexion (P < .001, effect size [ES] = 0.81) and knee-flexion excursion (P < .001, ES = 0.82) while producing increased peak ankle dorsiflexion (P = .006, ES = 0.31), ankle-dorsiflexion excursion (P < .001, ES = 0.31), peak knee-valgus angle (P = .02, ES = 0.21), and MKD (P < .001, ES = 2.92). During the W condition, VL (P = 0.002, ES = 0.33) and VMO (P = .049, ES = 0.20) activity decreased while soleus activity increased (P = .03, ES = 0.64) compared with the NW condition. No changes were seen in hip kinematics (P > .05).

Conclusions:

Altering ankle-dorsiflexion starting position during a double-leg squat resulted in increased knee valgus and MKD, as well as decreased quadriceps activation and increased soleus activation. These changes are similar to those seen in people with PFP.

Macrum is with the Dept of Athletics, University of Richmond, Richmond, VA. Bell is with the Dept of Kinesiology, University of Wisconsin–Madison, Madison, WI. Boling is with the Dept of Athletic Training and Physical Therapy, University of North Florida, Jacksonville, FL. Lewek is with the Dept of Allied Health Sciences, and Padua, the Dept of Exercise and Sport Science, University of North Carolina at Chapel Hill, Chapel Hill, NC.

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