Age-Related Differences in Kinematics, Kinetics, and Muscle Synergy Patterns Following a Sudden Gait Perturbation: Changes in Movement Strategies and Implications for Fall Prevention Rehabilitation

Abstract

Falls in older adults are leading causes of fatal and non-fatal injuries, negatively impacting quality of life among those in this demographic. Most elderly falls occur due to unrecoverable limb collapse during balance control in the single-limb support (SLS) phase. To understand why older adults are more susceptible to falls than younger adults, we investigated age-related differences in lower limb kinematics, kinetics, and muscle synergy patterns during SLS, as well as their relationship to postural control strategies. Thirteen older and thirteen younger healthy adults were compared during the SLS phase of balance recovery following an unexpected surface drop perturbation. Compared to younger adults, older adults demonstrated (1) greater trunk flexion, (2) increased hip extension torque and reduced hip abduction torque of the perturbed leg, and (3) higher postural sway. Trunk flexion was correlated with a delayed latency to the start of lateral-to-medial displacement of center of mass from the perturbation onset. The group-specific muscle synergy revealed that older adults exhibited prominent activation of the hip extensors, while younger adults showed prominent activation of the hip abductors. These findings provide insights into targeted balance rehabilitation and indicate ways to improve postural stability and reduce falls in older adults.

The influence of smoothness and speed of stand-to-sit movement on joint kinematics, kinetics, and muscle activation patterns

“…Previous studies have noted that, during the single-limb support (SLS) phase, knee extensor eccentric control of the perturbed leg served as the initial defense against potential falls following encountering ground surface challenges such as unexpected surface drop, slip, and trip ( Pai et al, 2006 ; Wang et al, 2019 ; Jeon et al, 2022 ). This is due to the direct correlation between the level of knee extensor eccentric control and the risk of limb collapse, which, in turn, is closely associated with falls ( Jeon et al, 2023b ). Even in cases where limb collapse is avoided in the vertical direction, a weakened, wobbly, and unstable perturbed leg during SLS can still potentially lead to irrecoverable instability in the both A-P and M-L directions, and this exacerbates the instability of the compensatory balance recovery reactions, such as subsequent stepping and arm movements.…”

“…Although StandTS may initially appear as a reverse movement of STS, a crucial distinction emerges as STS necessitates concentric knee extensor power, whereas StandTS relies significantly on knee extensor eccentric control to manage falling momentum against gravity. Notably, the effectiveness of eccentric control at the knee joint during the descending phase greatly influences potential fall risk ( Wang et al, 2019 ; Jeon et al, 2022 , 2023b , c ). Our findings also highlighted the pivotal role of knee extensor eccentric control in descending balance control during StandTS, and work at the knee joint is correlated with reduced vertical postural sway.…”

Age-related differences in lower limb muscle activation patterns and balance control strategies while walking over a compliant surface

“…Given that the mGas is a biarticular muscle, with attachments at both the ankle and knee joints, the mGas contributes to generating compressive shear force at the knee joint when the foot is dorsiflexed during the SLS 48 . The compressive shear force created by the mGas stabilizes the SLS balance by preventing anterior tibial translation and attenuating the valgus loading at the knee joint 5 , 49 .…”

“…While walking over multi-terrain surfaces, such as solid, compliant, rocky, irregular, slippery, and uneven surfaces, older adults demonstrate decreased gait speed, reduced step length, and increased variability in medial–lateral center of mass (CoM) acceleration and trunk roll 1 , 2 . Previous studies over firm, level ground surfaces have found that age-related impairment in neuromuscular control and force-generating capacity in the lower limbs lead to altered muscle activation patterns during walking balance recovery 3 – 5 . For example, neuromuscular control tends to become more simplistic with age, leading to reduced variability and efficiency of muscle synergy options 3 .…”

A Preliminary Study on How Combining Internal and External Focus of Attention in a Movement Language Can Improve Movement Patterns

“…(1) Pre-processing of sEMG signal: Any DC offset was first eliminated using the "detrend" function in MATLAB. Next, a median filter was applied to the signal to remove noise, followed by the application of a 20-450 Hz bandpass filter to extract the frequency range where muscular energy is concentrated [29][30][31].…”