Given that gait is a crucial indicator for evaluating motor function and balance in this age group, investigating impact of this muscle tightness on the biomechanical indices and characteristics of gait is of particular importance. Therefore, the present study was conducted with the aim of examining the effect of iliopsoas muscle tightness on the frequency spectrum of ground reaction forces during walking in older adults.

In this cross-sectional comparative study, 32 older adults aged 65 to 75 years were examined, divided into two groups: those with and those without iliopsoas muscle tightness. Muscle tightness was assessed using the Modified Thomas Test. Ground reaction forces in three directions were measured using a Bertec force plate with a sampling rate of 1000 Hz. The studied variables included the frequency corresponding to 99.5% power, the number of essential harmonics, median frequency, and frequency bandwidth. Data were analyzed using an independent t-test at a significance level of p < 0.05.

Comparison of the ground reaction force frequency spectra revealed that during walking, participants in the group with iliopsoas muscle tightness demonstrated larger median frequency and 99.5% power frequency values in the anterior-posterior, vertical, and free moment components compared to the healthy group.

Results indicate alterations in the frequency characteristics of the gait pattern in older adults with iliopsoas tightness. Accordingly, attention to rehabilitative and therapeutic interventions aimed at improving the flexibility and function of the iliopsoas muscle could be effective in modulating these alterations and optimizing the biomechanical indices of gait in this population.