Analysis of EEG-EMG Coherence in Low Frequency Bands

In this, study, an attempt is made to analyze the corticomuscular coupling of the brain and muscular system in the low-frequency components during ramp descent (RD) and stair descent (SD) locomotion. For this purpose, magnitude squared coherence (MSC) is computed from the simultaneous EEG and EMG signals recorded during the ramp and stair descent tasks. The MSC is extracted from the low- frequency bands such as delta (0.1–3 Hz) and theta bands (4–7 Hz). The study utilizes a publicly available database consisting of simultaneous recorded EEG, lower limb EMG and full body motion information from ten healthy subjects. The results show that there exists corticomuscular coupling between motor cortex (C1, C2 and Cz contacts) and tibialis anterior muscle activities during RD and SD. In addition, the MSC differs for both the tasks and frequency bands. In delta band frequencies, the MSC is found to be higher in C2 regions. In the case of theta, the MSC is higher in C1 during RD and in Cz during SD. Therefore, the MSC associated with the low frequency components could be used to detect walking intentions.

Finite element analysis of femoral neck strains during stair ascent and descent

For older population, a better understanding of the hip joint loading environment is needed for the prevention of hip pain, and the reduction of the stress fractures and fall risks. Using the motion analysis and inverse dynamics methods, combined with musculoskeletal modelling, static optimization, and finite element (FE) femur model, the difference of femoral neck strains between stair ascent vs. descent, young vs. older populations was compared. A two-way repeated-measures MANOVA was applied to test the effect of age and stair direction on the femoral neck strains. The strains at the femoral neck cross-section were greater for stair descent than ascent for both age groups (mostly P = 0.001 to 0006) but there was no difference between age groups. In this study, femoral neck strains represented bone loading environment in more direct ways than joint reaction forces/moments or joint contact forces, the risk of hip pain, falls and stress fractures might be greater during stair descent than ascent. Possible preventative methods to reduce these risks should be developed in the future studies.

Energy absorption at lower limb joints in different foot contact strategies while descending stairs

BACKGROUND: Joint loads in different walking strategies during stair descent have been investigated in terms of the joint moment in association with the risk of osteoarthritis. However, the absorption mechanisms of the potential energy loss are not known. OBJECTIVE: This study aims to compare the mechanical energy absorptions in lower limb joints in different initial foot contact strategies. METHODS: Nineteen young subjects walked down on instrumented stairs with two different strategies, i.e., forefoot and rearfoot strike. Power and energy at lower limb joints during stance phase were compared between strategies. RESULTS: Lower limb joints absorbed 73 ± 11% of the potential energy released by descending stairs and there was no difference between strategies. Rearfoot strategy absorbed less energy than forefoot strategy at the ankle joint in the 1st phase, which was compensated mainly by more energy absorption at the knee in the 2nd phase and less energy generation at the hip joints in the 3rd phase. CONCLUSION: The results suggest that a leg absorbs most of the potential energy while descending stairs irrespective of the walking strategies and that any reduction of energy absorption at one joint is compensated by other joints. Greater energy absorption at the knee joint compared to the other joints suggests high burden of knee joint muscles and connective tissues during stair-descent, which is even more significant for the rearfoot strike strategy.

Age-related differences in stair descent balance control: Are women more prone to falls than men?

Stair descent is one of the most common forms of daily locomotion and concurrently one of the most challenging and hazardous daily activities performed by older adults. Thus, sufficient attention should be devoted to this locomotion and to the factors that affect it. This study investigates gender and age-related differences in balance control during and after stair descent on a foam mat. Forty-seven older adults (70% women) and 38 young adults (58% women) performed a descent from one step onto a foam mat. Anteroposterior (AP) and mediolateral (ML) centre of pressure velocity (CoP) and standard deviation of the CoP sway were investigated during stair descent and restabilization. A two-way analysis of variance (ANOVA) revealed the main effects of age for the first 5 s of restabilization. Older women exhibited significantly higher values of CoP sway and velocity in both directions compared to the younger individuals (CoP SDAP5, 55%; CoP SDML5, 30%; CoP VAP5, 106%; CoP VML5, 75%). Men achieved significantly higher values of CoP sway and velocity only in the AP direction compared to their younger counterparts (CoP SDAP5, 50% and CoP VAP5, 79%). These findings suggest that with advancing age, men are at higher risk of forward falls, whereas women are at higher risk of forward and sideways falls.