National Physical Therapy Examination (NPTE) Practice Exam 2025 – The All-in-One Guide to Exam Success!

A grade II strain of the iliopsoas muscle, which primarily acts as a hip flexor, would most significantly affect the phases of the gait cycle that require hip flexion. During the toe-off (pre-swing) phase, the iliopsoas is essential for lifting the leg and initiating the swing phase by flexing the hip. Similarly, in the acceleration (initial swing) phase, the muscle plays a critical role in flexing the hip to bring the leg forward.

In contrast, the other phases mentioned do not rely as heavily on the iliopsoas. For instance, in heel strike (initial contact), the demand for hip flexion is not as pronounced, and the loading response (foot flat) phase involves more eccentric control rather than the power of hip flexion. Midstance and deceleration (terminal swing) also engage the iliopsoas to a lesser extent than the key phases identified, focusing more on stabilization rather than active flexion.

Therefore, recognizing the primary role of the iliopsoas as a hip flexor highlights why the toe-off and acceleration phases of the gait cycle would be the most impacted by a grade II strain of this muscle.