Muscle activation profile is modulated by unexpected balance loss in walking

Gait and sEMG characteristics of lower limbs in children with unilateral spastic cerebral palsy during walking

BACKGROUND

Children with unilateral spastic cerebral palsy (USCP) have muscle hypertonia, balance, and coordination defects that affect gross motor skills, especially walking. Understanding the gait characteristics and lower limb muscle activation patterns of USCP children can provide an objective and quantitative basis for patient assessment and treatment plan formulation.

OBJECTIVE

This study compared the gait and lower limb muscle activation characteristics of children with USCP and with typical development (TD) during walking.

METHODS

We recorded gait and sEMG data of 20 children with USCP, and 20 with typical development. sEMG signals were acquired from the bilateral tibialis anterior (TA) and lateral gastrocnemius muscles (LG) during walking. The root mean square (RMS) value, integrated electromyographic (iEMG) value and co-contraction ratio (CR) were used to evaluate muscle activity. Student's t Test and non-parametric rank sum Test were used to compare the differences between the data groups (significance level of 0.05).

RESULTS

The stance time, step length, speed, single leg support time ratio, ground impact, pre-swing angle, and muscle strength of the affected side were significantly decreased compared to those of the unaffected side in children with USCP (P < 0.05), while the swing phase, muscle tonus of LG were significantly prolonged (P < 0.05). Compared with TD children, children with USCP exhibited reduced bilateral walking ability, particularly noticeable in their smaller pre-swing angle(P < 0.05), diminished muscle strength of the TA and LG, as well as LG spasms(P < 0.05).

SIGNIFICANCE

Children with USCP have decreased ambulatory gait stability. Step length, pull acceleration, pre-swing angle, and CR can be used as sensitive indicators for gait assessment. Strengthening the TA muscle and reducing ankle spasm may help improve gait and postural stability in children with USCP.

Upward perturbations trigger a stumbling effect

BACKGROUND

Vertical perturbations are one major cause of falling. Incidentally, while conducting a comprehensive study comparing effects of vertical versus horizontal perturbations, we commonly observed a stumbling-like response induced by upward perturbations. The present study describes and characterizes this stumbling effect.

METHODS

Fourteen individuals (10 male; 27 ± 4 yr) walked self-paced on a treadmill embedded in a moveable platform and synchronized to a virtual reality system. Participants experienced 36 perturbations (12 types). Here, we report only on upward perturbations. We determined stumbling based on visual inspection of recorded videos, and calculated stride time and anteroposterior, whole-body center of mass (COM) distance relative to the heel, i.e., COM-to-heel distance, extrapolated COM (xCOM) and margin of stability (MOS) before and after perturbation.

RESULTS

From 68 upward perturbations across 14 participants, 75% provoked stumbling. During the first gait cycle post-perturbation, stride time decreased in the perturbed foot and the unperturbed foot (perturbed = 1.004 s vs. baseline = 1.119 s and unperturbed = 1.017 s vs. baseline = 1.125 s, p < 0.001). In the perturbed foot, the difference was larger in stumbling-provoking perturbations (stumbling: 0.15 s vs. non-stumbling: 0.020 s, p = 0.004). In addition, the COM-to-heel distance decreased during the first and second gait cycles after perturbation in both feet (first cycle: 0.58 m, second cycle: 0.665 m vs. baseline: 0.72 m, p-values<0.001). During the first gait cycle, COM-to-heel distance was larger in the perturbed foot compared to the unperturbed foot (perturbed foot: 0.61 m vs. unperturbed foot: 0.55 m, p < 0.001). MOS decreased during the first gait cycle, whereas the xCOM increased during the second through fourth gait cycles post-perturbation (maximal xCOM at baseline: 0.5 m, second cycle: 0.63 m, third cycle: 0.66 m, fourth cycle: 0.64 m, p < 0.001).

CONCLUSIONS

Our results show that upward perturbations can induce a stumbling effect, which - with further testing - has the potential to be translated into balance training to reduce fall risk, and for method standardization in research and clinical practice.

The Effect of Human Settlement Pedestrian Environment on Gait of Older People: An Umbrella Review

Older people are limited by the pedestrian environment in human settlements and are prone to travel difficulties, falls, and stumbles. Furthermore, we still lack systematic knowledge of the pedestrian environment affecting the gait of older people. The purpose of this review is to synthesize current evidence of effective human settlement pedestrian environments interfering with gait in older people. The systematic effects of the human settlement pedestrian environment on gait in older people are discussed. Databases such as Web of Science, Medline (via PubMed), Scopus, and Embase were searched for relevant studies up to June 2022. The literature was screened to extract relevant evidence from the included literature, assess the quality of the evidence, and analyze the systematic effects of the pedestrian environment on gait in older people. From the 4297 studies identified in the initial search, 11 systematic reviews or meta-analysis studies were screened, from which 18 environmental factors and 60 gait changes were extracted. After removing duplicate elements and merging synonymous features, a total of 53 relationships between environmental factors and gait change in older people were extracted: the main human settlement pedestrian environmental factors affecting gait change in older people in existing studies were indoor and outdoor stairs/steps, uneven and irregular ground, obstacles, walking path turns, vibration interventions, mechanical perturbation during gait, and auditory sound cues. Under the influence of these factors, older people may experience changes in the degree of cautiousness and conservatism of gait and stability, and their body posture performance and control, and muscle activation may also be affected. Factors such as ground texture or material, mechanical perturbations during gait, and vibration interventions stimulate older people's understanding and perception of their environment, but there is controversy over the results of specific gait parameters. The results support that human settlements' pedestrian environment affects the gait changes of older people in a positive or negative way. This review may likely contribute evidence-based information to aid communication among practitioners in public health, healthcare, and environmental construction. The above findings are expected to provide useful preference for associated interdisciplinary researchers to understand the interactions among pedestrian environments, human behavior, and physiological characteristics.

Perturbations during Gait: A Systematic Review of Methodologies and Outcomes

BACKGROUND

Despite extensive literature regarding laboratory-based balance perturbations, there is no up-to-date systematic review of methods. This systematic review aimed to assess current perturbation methods and outcome variables used to report participant biomechanical responses during walking.

METHODS

Web of Science, CINAHL, and PubMed online databases were searched, for records from 2015, the last search was on 30th of May 2022. Studies were included where participants were 18+ years, with or without clinical conditions, conducted in non-hospital settings. Reviews were excluded. Participant descriptive, perturbation method, outcome variables and results were extracted and summarised. Bias was assessed using the Appraisal tool for Cross-sectional Studies risk of bias assessment tool. Qualitative analysis was performed as the review aimed to investigate methods used to apply perturbations.

RESULTS

644 records were identified and 33 studies were included, totaling 779 participants. The most frequent method of balance perturbation during gait was by means of a treadmill translation. The most frequent outcome variable collected was participant step width, closely followed by step length. Most studies reported at least one spatiotemporal outcome variable. All included studies showed some risk of bias, generally related to reporting of sampling approaches. Large variations in perturbation type, duration and intensity and outcome variables were reported.

CONCLUSIONS

This review shows the wide variety of published laboratory perturbation methods. Moreover, it demonstrates the significant impact on outcome measures of a study based on the type of perturbation used.

REGISTRATION

PROSPERO ID: CRD42020211876.