Leg Muscle Activity and Similarity Indexes during Stance Tests in the Elderly

Objective: The total time for double-leg, tandem, and left and right single-leg stances (DLS, TS, L-SLS and R-SLS) is often used to evaluate the stability of the elderly. To provide a detailed information of the elderly motor control ability, muscle activity data are essential.<br/>Background: Several stance tests have been used to assess the likelihood of future falls in older adults. Incorporating muscle activity data into stability analysis, alongside stance tests, would provide a more reliable quantitative indicator of postural stability. <br/>Method: We collected surface electromyography (sEMG) data from six muscles in each leg of 22 elderly participants (70.3±4.2 years old) and evaluated them using the brain motor control assessment (BMCA) protocol, focusing on magnitude and similarity index (SI). Fifteen participants who could hold maintain stances for at least 10 seconds or longer formed the control group, while seven participants who held the stances for less than 10 seconds were placed in the test group.<br/>Results: For the right single-leg stance (R-SLS), the control group showed 28.1(±3.5) seconds, while the test group averaged 8.9(±4.6) seconds. The total average EMG magnitude for all stances in the control group was 120.0(±45.6)uV, compared to 131.6(±75.5)uV in the test group (p > 0.56). The SI was 0.94(±0.04) for the control group and 0.84(±0.15) for the test group (p < 0.02). No significant difference was found between right and left side. Notably, two test group participants had low SI values for all stances (average SI = 0.69±0.16 and 0.60±0.12).<br/>Conclusion: We applied the BMCA protocol to analyze sEMG patterns in healthy older adults during standing tests. The similarity index shows promise as an effective screening tool for identifying those at risk of stability issues. Additionally, the BMCA protocol could be useful for monitoring motor control abilities in older adults across various stability tests.<br/>Application: This study used the BMCA protocol to evaluate sEMG during these stances, suggesting that SI and maintenance time could be effective screening tools for identifying elderly individuals with balance difficulties.