Changes in Iliopsoas Muscle Activity and Hip/Pelvic Kinematics With Variations in Step Length and Cadence at a Fixed Walking Speed.

BACKGROUND

Older adults often compensate for reduced mobility by adopting shorter steps and a faster cadence, which may alter muscle recruitment and joint kinematics. The iliopsoas, a key muscle for leg swing and posture control, is particularly affected. Understanding its role across different gait patterns may help improve gait training and fall prevention.

PURPOSE

To investigate how step length and cadence influence iliopsoas muscle activation and hip/pelvic kinematics during treadmill walking at a constant speed.

METHODS

Ten healthy young men walked on a treadmill at 5 km/h under three conditions: (1) Step-Length Increased Walking (SL), longer steps with lower cadence; (2) Normal Walking (N), self-selected gait; and (3) Pitch Increased Walking (P), shorter steps with higher cadence. Iliopsoas activity was measured using surface electromyography, and hip/pelvic motion was captured using 3D motion analysis. The gait cycles were divided into four functional phases for phase-specific analysis. Nonparametric tests were used to compare muscle activity across conditions.

RESULTS

Iliopsoas activity was significantly higher during the early (Phase 1) and late stance (Phase 2) in both the SL and P conditions than in the N condition. During the late swing (Phase 4) period, the SL condition elicited the greatest iliopsoas activation accompanied by increased hip flexion and pelvic tilt. This phase showed the strongest effect size among all phases, highlighting the critical role of iliopsoas during terminal swing. P walking also showed elevated iliopsoas activation during the stance, likely due to the faster step cycle.

CONCLUSION

The findings suggest that step length and cadence influence the timing and magnitude of iliopsoas activation. Longer steps increase activation during the late swing phase, while a higher cadence enhances activation during stance. Phase-specific training targeting iliopsoas strength and hip flexion mobility may help improve gait performance.