Surface Electromyographic Characteristics of Lower Limb Muscles in Frail Older Adults With Cardiovascular Disease: A Case-Control Study.

BACKGROUND

Frailty predicts poor outcomes in older adults with cardiovascular disease (CVD) and is closely related to neuromuscular dysfunction. Lower limb surface electromyography (sEMG) during walking may capture frailty-related motor alterations, but its characteristics and discriminative value in older adults with CVD remain unclear. This study aimed to compare lower limb sEMG features between frail and nonfrail older adults with CVD and evaluate their ability to identify frailty.

METHODS

This case-control study included 150 older adults with CVD (75 frail, 75 nonfrail; 80 men, 70 women). Frailty was defined using the Fried frailty phenotype. Wireless sEMG signals were recorded bilaterally from the rectus femoris, semitendinosus, tibialis anterior and medial gastrocnemius during a standardized 10-m walk test. Time-domain parameters, frequency-domain parameters, symmetry indices, contribution ratios and activation-sequence rank were compared with false-discovery-rate correction. Binary logistic regression and receiver operating characteristic (ROC) analysis were used to identify factors independently associated with frailty and evaluate discriminative performance.

RESULTS

Frail participants were older (76.04 ± 7.57 vs. 68.55 ± 6.09 years), more frequently exposed to polypharmacy (93.33% vs 70.67%), required longer to complete the 10-m walk test (13.34 ± 3.23 vs. 9.44 ± 1.21 s) and had lower Tinetti Performance-Oriented Mobility Assessment (POMA) scores (21.51 ± 4.27 vs. 27.59 ± 0.92; all p < 0.001). The frail group showed higher median integrated EMG (IEMG) of the left semitendinosus (534.4 [451.3, 680.7] vs. 455.5 [384.5, 542.0] μV·s, FDR-adjusted p = 0.0084) and higher activation-sequence rank of the left rectus femoris (4.333 [3.000, 5.667] vs. 3.333 [2.333, 4.333], FDR-adjusted p = 0.0404). In the frequency domain, median frequency (MF) was higher in the right rectus femoris, bilateral tibialis anterior and right medial gastrocnemius, whereas mean power frequency (MPF) was higher in six muscles (all FDR-adjusted p < 0.05). In multivariable analysis, MF of the right rectus femoris (OR = 1.067, 95% CI 1.003-1.135, p = 0.038), MF of the right medial gastrocnemius (OR = 1.054, 95% CI 1.009-1.102, p = 0.019), activation-sequence rank of the right tibialis anterior (OR = 0.640, 95% CI 0.448-0.914, p = 0.014), age (OR = 1.128, 95% CI 1.044-1.218, p = 0.002) and Tinetti POMA score (OR = 0.784, 95% CI 0.669-0.918, p = 0.003) were independently associated with frailty. The sEMG + age model achieved an area under the curve (AUC) of 0.8418 (sensitivity = 0.8933; specificity = 0.6400), approaching the full model including Tinetti POMA score (AUC = 0.8740; sensitivity = 0.9200; specificity = 0.7067).

CONCLUSIONS

Lower limb sEMG features during walking were independently associated with frailty in older adults with CVD. The simplified sEMG + age model showed good discriminative performance and may provide candidate objective markers to complement conventional frailty assessment.