Background: Stability during standing is achieved by a complex coordination process between various human systems. The stability of normal subjects and patients with various neuromuscular disorders has been evaluated by common methods based on force plate data analysis for one minute. However, most of the people frequently stand for a prolonged period during daily activities.
Objectives: This study aimed to evaluate the stability of subjects during a longer period of time. Moreover, the new method was introduced to analyze the stability of subjects with musculoskeletal disorders.
Study design: Experimental.
Methods: Four groups of normal adults and children, individuals with spinal cord injury (SCI) and Perthes disease were recruited in this study. Stability of the subjects was evaluated by using parameters collected from centre of pressure (COP) sways obtained while subjects standing on force plate for one and then five minutes based on the old and new methods. Two sample t-test was used to compare the stability of the subjects by the commonly used method. The number of stable to unstable frames was selected for final analysis based on the new method.
Results: Based on the traditional method, the SCI and Perthes patients were more stable than normal subjects (p < 0.05). Moreover, children were more unstable in the anteroposterior plane than adults. However, based on the new method, SCI and patients with Perthes disease were more unstable than normal adults. Moreover, in mediolateral direction the results of stability analysis with the new method differed from that of the traditional method.
Conclusion: The new method of stability analysis seems to be more sensitive and accurate than that of the traditional commonly used method. Based on the new method, stability is the ability of a subject to return from an unstable position to a stable one and to remain in a stable one for a certain period of time. Clinical relevance The results of this research can be used by most clinicians to evaluate the stability of subjects with various musculoskeletal disorders.