Parkinson’s disease (PD) is a neurodegenerative disease characterized by motor symptoms, including muscle rigidity, assessed subjectively using scales such as the Movement Disorder Society - Unified Parkinson’s Disease Rating Sclae (MDS-UPDRS). This study explores the use of accelerometer signals and power spectral density (PSD) analysis to objectively measure rigidity. Data from healthy and PD participants, in “on" and “off" states of medication (with and without) were collected using inertial sensors on the wrist. Preprocessing was applied to ensure good data quality and PSD was calculated, revealing distinct trends in healthy and PD individuals. In the “off" state, the levels of rigidity assessed by UPDRS are correlated with changes in PSD. Spectral analysis shows a progressive decrease in PSD as a function of rigidity, indicating an impairment of muscle function in the “off" state. Healthy individuals exhibit higher power amplitudes in the evaluated frequencies. The Kruskal-Wallis test confirmed significant differences between the different groups. In conclusion, the study was able to differentiate healthy and PD groups based on the characteristics of their PSD, highlighting the potential of this technique in the development of equipment dedicated to the evaluation of rigidity.