Merged swing-muscle synergies and their relation to walking characteristics in subacute post-stroke patients: An observational study

Diverse Plantarflexor Module Characteristics Influence Immediate Effects of Plastic Ankle-Foot Orthosis on Gait Performance in Patients With Stroke: A Cross-sectional Study

OBJECTIVE

To investigate the immediate effects of plastic ankle-foot orthosis (AFO) on locomotor performance in patients with stroke and determine how such effects might undergo alteration when distinct plantarflexor (PF) module subtypes are considered.

DESIGN

Cross-sectional study.

SETTING

Two university hospitals.

PARTICIPANTS

Fifty-two patients with stroke and 21 of those without stroke (N=73).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Motor modules were identified through non-negative matrix factorization, and participants were classified into 3 groups: independent-normal-timing, independent-altered-timing, and merged PF modules. To assess the effects of the AFO, gait measurements reflecting locomotor performance were obtained with and without the presence of the plastic AFO for each group.

RESULTS

The independent-altered-timing group had increased paretic propulsion, greater non-paretic step length, and faster walking speed after the administration of the plastic AFO; however, these significant changes were not observed in the independent-normal-timing and merged PF module groups. Notably, patients in the independent-normal-timing and merged PF module groups exhibited longer paretic stance times.

CONCLUSION

This study suggests that the immediate effects of plastic AFO depend on the PF module subtype. These findings can potentially guide clinical decision-making regarding AFO selection for stroke rehabilitation in patients with diverse gait control characteristics.

Speed-dependent modulations of muscle modules in the gait of people with radiographical and asymptomatic knee osteoarthritis and elderly controls: Case-control pilot study

This study investigates the muscle modules involved in the increase of walking speed in radiographical and asymptomatic knee osteoarthritis (KOA) patients using tensor decomposition. The human body possesses redundancy, which is the property to achieve desired movements with more degrees of freedom than necessary. The muscle module hypothesis is a proposed solution to this redundancy. While previous studies have examined the pathological muscle activity modulations in musculoskeletal diseases such as KOA, they have focused on single muscles rather than muscle modules. Moreover, most studies have only examined the gait of KOA patients at a single speed, leaving the way in which gait speed affects gait parameters in KOA patients unclear. Assessing this influence is crucial for determining appropriate gait speed and understanding why preferred gait speed decreases in KOA patients. In this study, we apply tensor decomposition to muscle activity data to extract muscle modules in KOA patients and elderly controls during walking at different speeds. We found a muscle module comprising hip adductors and back muscles that activate bimodally in a gait cycle, specific to KOA patients when they increase their walking speed. These findings may provide valuable insights for rehabilitation for KOA patients.

Characteristics of limb kinematics in the gait disorders of post-stroke patients

Post-stroke gait disorders involve altered lower limb kinematics. Recently, the endpoint of the lower limb has been used as a control variable to understand gait kinematics better. In a cross-sectional study of sixty-seven post-stroke patients, the limb extension angle and effective limb length during gait were used as input variables with a mixed Gaussian model-based probabilistic clustering approach to identify five distinct clusters. Each cluster had unique characteristics related to motor paralysis, spasticity, balance ability, and gait strategy. Cluster 1 exhibited high limb extension angle and length values, indicating increased spasticity. Cluster 2 had moderate extension angles and high limb lengths, indicating increased spasticity and reduced balance ability. Cluster 3 had low limb extension angles and high limb length, indicating reduced balance ability, more severe motor paralysis, and increased spasticity. Cluster 4 demonstrated high extension angles and short limb lengths, with a gait strategy that prioritized stride length in the component of gait speed. Cluster 5 had moderate extension angles and short limb lengths, with a gait strategy that prioritized cadence in the component of gait speed. These findings provide valuable insights into post-stroke gait impairment and can guide the development of personalized and effective rehabilitation strategies.

Characteristics of muscle synergy and anticipatory synergy adjustments strategy when cutting in different angles

BACKGROUND

Cutting is a quick change of direction that challenges body balance and stability. As the cut-angle increases, the elite athlete can achieve higher performance by pre-adjusting the posture of the lower limb joints. However, it is unclear how the cut-angle affects the neuromuscular control of cutting and the step before cutting, which is essential for daily training and preventing injury in large-angle cutting.

RESEARCH QUESTION

The purpose of this study was to determine how neuromuscular control strategies change under different angles for cutting and the step before cutting METHODS: Non-negative matrix factorisation and K-means clustering were used to extract muscle synergy in the trunk and lower limbs of 12 athletes when cutting at different angles. Uncontrolled manifold analysis was used to clarify whether the muscle synergy fluctuations in the step before cutting were beneficial in stabilising the COP during the cutting.

RESULTS

This study found that the angle did not affect the number of muscle synergies either in the cutting or the step before the cutting. As the angle increases, the activation timing of synergy module 2 during cutting moves forward and is tightly integrated with module 1. The combined synergy at 90° accounted for the largest proportion of either cutting or the step before cutting and had a lower synergy index.

SIGNIFICANCE

Muscle synergy can respond to large-angle cutting through flexible combinations. The muscle synergy for 90° cutting is less regular and has a lower degree of anticipatory synergy adjustments, which may result in poorer postural stability and an increased risk of lower limb joint injury during cutting.

Association between temporal asymmetry and muscle synergy during walking with rhythmic auditory cueing in stroke survivors living with impairments

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We examined the effect of temporal gait asymmetry on muscle synergy post stroke.

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In our design, the temporal asymmetry during gait was experimentally modulated.

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The temporal asymmetry was modulated using rhythmic auditory cueing.

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Rhythmic auditory cueing with gait immediately improved temporal asymmetry and muscle synergy deficits.

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The temporal asymmetry affected muscle synergy more than kinematics.

Objective

To examine the relationship between temporal asymmetry and complexity of muscle synergy during walking using rhythmic auditory cueing (RAC) and the factors related to changes in muscle synergy during walking with RAC in survivors of stroke.

Design

Cross-sectional study.

Setting

Wards at 2 medical corporation hospitals.

Participants

Forty survivors of stroke (N=40; mean age, 70.4±10.3 years; time since stroke, 72.2±32.3 days) who could walk without physical assistance.

Interventions

Not applicable.

Main Outcome Measures

The participants were assessed in a random block design under 2 conditions: comfortable walking speed (CWS) and walking with RAC. Single-leg support time, kinematics, and electromyograms were measured. Factors related to the complexity of muscle synergy (variance accounted for by 1 synergy [VAF1]) between the walking conditions were examined using hierarchical multiple regression analysis.

Results

In the RAC condition, lower limb flexion and knee flexion angles, single-leg support time on the paretic side, and the symmetry index of single-leg support time were increased compared with those in the CWS condition. VAF1 was decreased in the RAC condition (73.9±0.15) compared with that in the CWS condition (76.9±0.13, P=.002). Hierarchical multiple regression analysis revealed that the change in VAF1 was explained by change in single-leg support time (R²=0.43, P=.002).

Conclusions

The RAC condition demonstrated a more complex representation of muscle synergy than the CWS condition; the change in single-leg support time on the paretic side related to the changes in muscle synergy more than changes in lower limb angle. These findings can help in the walking-training concept to improve muscle synergy deficits in survivors of stroke.