Limiting Ankle Dorsiflexion Range of Motion Alters Lower Extremity Kinematics and Muscle Activation Patterns during a Squat
CONTEXT:
Limitations in gastrocnemius/soleus flexibility, which restricts ankle dorsiflexion during dynamic tasks, have been reported in individuals with patellofemoral pain (PFP) and are theorized to play a role in the development of PFP.
OBJECTIVE:
To determine the effect of restricted ankle dorsiflexion range of motion (ROM) on lower extremity kinematics and muscle activity (EMG) during a squat. We hypothesized that restricted 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 two conditions: a no-wedge condition (NW) with the foot flat on the floor and a wedge condition (W) with a 12 forefoot angle, to simulate reduced plantarflexor flexibility.
MAIN OUTCOME MEASURES:
Three-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 to the NW condition, the wedge produced decreased peak knee flexion (P < 0.001, Effect Size (ES) = 0.81) and knee flexion excursion (P < 0.001, ES = 0.82); while producing increased peak ankle dorsiflexion (P = 0.006, ES = 0.31), ankle dorsiflexion excursion (P < 0.001, ES = 0.31), peak knee valgus angle (P = 0.02, ES = 0.21), and MKD (P < 0.001, ES = 2.92). During the W condition, VL (P = 0.002, ES = 0.33) and VMO (P = 0.049, ES = 0.20) activity decreased while soleus activity increased (P = 0.03, ES = 0.64) compared to the NW condition. No changes were seen in hip kinematics (P > 0.05).
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.