Comparison of mean frequency and median frequency in evaluating muscle fiber type selection in varying gait speed across healthy young adult individuals

Muscle activation profile is modulated by unexpected balance loss in walking

BACKGROUND

During an unexpected loss of balance, avoiding a fall requires people to readjust their footing rapidly and effectively. A deeper understanding of muscle activation patterns in response to unexpected balance loss will provide insights into the mechanisms of balance recovery responses. This could have implications for treatment of people with balance deficits.

RESEARCH QUESTION

Explore the differences in balance recovery responses to perturbations in different phases of the gait cycle (single-support vs. double-support) in terms of biomechanical behavior (i.e., stepping and dynamic stability characteristics) and lower-limb muscle activation patterns.

METHODS

Muscle activation patterns of the ankle and knee muscles and muscle fiber type recruitment resulting from unannounced, mediolateral (i.e., right/left) horizontal-surface perturbations during walking was investigated in twenty healthy adults (27.00 ± 2.79 years, ten females). Surface electromyography (sEMG) total spectral power for specific frequency bands (40-60 Hz, 60-150 Hz, 150-250 Hz, 250-400 Hz and 400-1000 Hz), from tibialis anterior (TA) and vastus lateralis (VL) muscles were analyzed. Three mixed-effects models assessed behavioral and lower-limb muscle activation patterns resulting from perturbations in the gait cycle's single- and double-support phases. Statistical significance was set a priori at p < 0.05.

RESULTS

Compared to non-perturbed walking, we found a significant increase in the total spectral power of lower-extremity muscles during the first three seconds after perturbation. During the double-support phase of gait, we found a different muscle fiber type recruitment pattern between VL and TA muscles. However, there were no significant differences between VL and TA muscles for perturbations implemented in single-support phases.

SIGNIFICANCE

Our findings support the notion that muscle operating frequency is modulated in real-time to fit functional goal requirements, such as a rapid change of footing in response to unexpected loss of balance in single and double-support phases of gait.

Synergistic recruitment of multi-scale myoelectric oscillations of upper limb during infant crawling

It has been widely accepted that the central nervous system (CNS) modulates muscle synergies to simplify motion control. However, it is still unclear that if there is a synergistic recruitment strategy to organize oscillation components of surface electromyography (sEMG) signals for limb movement. The sEMG signals were recorded from bilateral biceps brachii (BB) and triceps brachii (TB) muscles during infant crawling. The multivariate empirical mode decomposition (MEMD) was applied to decompose multi-channel sEMG signals into multi-scale oscillations. Then, non-negative matrix factorization (NMF) method was employed to extract oscillation synergy patterns. The results indicated that there were three stable oscillation synergies in sEMG signals for crawling movement, and the recruitment coefficient curves reflected the role of muscle during crawling movement. Our preliminary work suggested that synergistic recruitment of multi-scale oscillation components maybe a new way to understand the organization of MU recruitment strategy by the CNS.