Changes in the symmetry of external perturbations affect patterns of muscle activity during gait initiation

Lee, Yun-Ju

doi:10.1016/j.gaitpost.2018.09.023

Cited by 7 publications

(5 citation statements)

References 31 publications

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“…To estimate the magnitude of muscle activity, EMG integrals (IntEMGi) were calculated during two 300 ms windows: (1) anticipatory postural adjustment (APA), from − 250 to + 49 ms; and (2) compensatory postural adjustment (CPA), from + 50 to + 349 ms (Santos et al 2010a ). Then, each integral was corrected by its corresponding baseline activity and normalized by the absolute maximum value across all conditions for each muscle and participant, respectively (Lee 2019 ): where i stands for each of the 16 muscles tested.…”

Section: Methodsmentioning

confidence: 99%

Older adults can rely on an auditory cue to generate anticipatory postural adjustments prior to an external perturbation

2022

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To minimize the potential postural disturbance induced by predictable external perturbations, humans generate anticipatory postural adjustments (APAs) using visual information about a perturbation. However, it is unknown whether older adults can generate APAs relying on auditory information. Ten older adults received external perturbations (a) with visual information but no auditory information available, (b) without neither visual nor auditory information, (c) with both visual and auditory information available, and (d) participated in training with only auditory information available. In addition, they were tested again after 1 week of washout period. Electromyography activities of eight leg and trunk muscles and ground reaction forces were recorded and analyzed during the anticipatory and compensatory phases. Outcome measures included the latencies and integrals of muscle activities, and center-of-pressure displacements. After a short period of training, participants were able to rely on the auditory cue only to generate APAs close to that when the visual information was available. In addition, after 1 week of washout period, they were able to partially retain the skill to rely on auditory cues to generate APAs. The outcome provides a foundation for future studies focusing on utilizing auditory cues to optimize postural control in individuals who have balance or vision deficit.

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Section: Methodsmentioning

confidence: 99%

Older adults can rely on an auditory cue to generate anticipatory postural adjustments prior to an external perturbation

2022

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“…A pendulum with a 30 cm long wooden stick and a flag was used to induce perturbations at the shoulder level on the right side of the body and allowed the participants to see the approaching pendulum via peripheral vision without a need for head rotation shown in Fig. 1 18 . The length of the central rod of the pendulum was adjusted to each individual’s shoulder height.…”

Section: Methodsmentioning

confidence: 99%

“…The external perturbation (pendulum impact) in the anterior-posterior direction during step initiation was shown to be a side-specific muscle coordination associated with both asymmetric perturbation and corresponding stance or swing leg side 18 . In spite of disturbed balance in the anterior-posterior direction, capacity of controlling ML postural stability has been associated with falls in older adults 19,20 .…”

Section: Introductionmentioning

confidence: 99%

Characteristics of medial-lateral postural control while exposed to the external perturbation in step initiation

Lee

Liang

Chen

et al. 2019

Sci Rep

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Controllability of posture in the medial-lateral direction is critical for balance maintenance, particularly in step initiation. The objective of the current study was to examine the effects of external perturbation and landing orientation on medial-lateral control stability in step initiation. Eleven young healthy participants stood on the force platform and waited for the instruction of taking a step while experiencing a pendulum perturbation applied at the lateral side of the right shoulder. Eight experimental conditions were conducted by two levels of step side (right or left), two levels of perturbation (with or without), and two levels of landing orientation (forward or diagonal). The center of pressure (COP), pelvic movements, and muscle activities were recorded and analyzed as the onset of COP and pelvic movement, the COP displacement, and cocontraction and reciprocal muscle activation pattern. The temporal events of COP and pelvic movement were not significantly different in all experimental conditions. However, COP and pelvic movement were significantly later in the diagonal condition. Most of the segments showed reciprocal muscle activation patterns in relation to the perturbation released time. Subsequently, all segments showed cocontraction muscle activation patterns, which was significantly affected by step side, perturbation, and orientation. The results suggest that how the CNS initiated a step was identical with the COP then pelvic movement. The outcome highlights the importance of external perturbation and foot landing orientation effects on postural adjustments, which may provide a different approach to help step initiation.

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“…Hence, the spectral analysis approach might be useful to identify the effects of sound on changes in postural regulations. Although older adults have shown less efficient postural control [15], previous studies of postural control generally focused on body sway in quiet standing [16,17], and instant limb movements, such as pushing tasks [18,19] or gait initiation [20,21]. These instant limb movements have been considered as a dual-task perturbation to standing balance and significantly affected changes in COP displacements [18,19,21].…”

Section: Introductionmentioning

confidence: 99%

Sound Effects on Standing Postural Strategies in the Elderly via Frequency Analysis Approach

Lee

Chen

et al. 2020

Applied Sciences

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Sound and sound frequency could improve postural sway in the elderly. The power spectrum intervals of the center of pressure (COP) displacement are associated with different postural regulations, which could be revealed by frequency analysis. The aim of the study was to investigate the effects of sound on dual-tasking postural control and conduct frequency analysis to distinguish postural regulations in the elderly. Fifteen young and 15 older healthy participants were instructed to stand on a force platform and performed the Purdue Pegboard test while hearing 50 dB sounds with sound frequencies of 250 Hz, 1000 Hz, 4000 Hz, or no sound. The total excursion, velocity, sway area, and power spectrum of low-, medium-, and high-frequency bands of the COP displacement were calculated in the anterior–posterior and medial–lateral directions. The percentages of low-frequency and medium-frequency bands in both directions were significantly different between with and without sound conditions, but not affected by sound frequency. Older adults showed a smaller percentage of low-frequency, larger percentage of medium-frequency, larger total COP excursion, and faster velocity in the medial–lateral direction. The outcome of the study supports the frequency analysis approach in evaluating sound effects on postural strategies in dual-tasking and reveals older adults utilize vestibular regulation as the primary postural strategy when the dual-task required visual attention.

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Changes in the symmetry of external perturbations affect patterns of muscle activity during gait initiation

Cited by 7 publications

References 31 publications

Older adults can rely on an auditory cue to generate anticipatory postural adjustments prior to an external perturbation

Older adults can rely on an auditory cue to generate anticipatory postural adjustments prior to an external perturbation

Characteristics of medial-lateral postural control while exposed to the external perturbation in step initiation

Sound Effects on Standing Postural Strategies in the Elderly via Frequency Analysis Approach

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