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

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.

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.