Associations Between Practice-Related Changes in Motor Performance and Muscle Activity in Healthy Individuals: A Systematic Review

The influence of pain and kinesiophobia on motor control of the upper limb: how pointing task paradigms can point to new avenues of understanding

ABSTRACT

People experiencing kinesiophobia are more likely to develop persistent disabilities and chronic pain. However, the impact of kinesiophobia on the motor system remains poorly understood. We investigated whether kinesiophobia could modulate shoulder pain-induced changes in (1) kinematic parameters and muscle activation during functional movement and (2) corticospinal excitability. Thirty healthy, pain-free subjects took part in the study. Shoulder, elbow, and finger kinematics, as well as electromyographic activity of the upper trapezius and anterior deltoid muscles, were recorded while subjects performed a pointing task before and during pain induced by capsaicin at the shoulder. Anterior deltoid cortical changes in excitability were assessed through the slope of transcranial magnetic stimulation input-output curves obtained before and during pain. Results revealed that pain reduced shoulder electromyographic activity and had a variable effect on finger kinematics, with individuals with higher kinesiophobia showing greater reduction in finger target traveled distance. Kinesiophobia scores were also correlated with the changes in deltoid corticospinal excitability, suggesting that the latter can influence motor activity as soon as the motor signal emerges. Taken together, these results suggest that pain and kinesiophobia interact with motor control adaptation.

Unexpected running perturbations: Reliability and validity of a treadmill running protocol with analysis of provoked reflex activity in the lower extremities

Introduction

Balance is vital for human health and experiments have been conducted to measure the mechanisms of postural control, for example studying reflex responses to simulated perturbations. Such studies are frequent in walking but less common in running, and an understanding of reflex responses to trip-like disturbances could enhance our understanding of human gait and improve approaches to training and rehabilitation. Therefore, the primary aim of this study was to investigate the technical validity and reliability of a treadmill running protocol with perturbations. A further exploratory aim was to evaluate the associated neuromuscular reflex responses to the perturbations, in the lower limbs.

Methods

Twelve healthy participants completed a running protocol (9 km/h) test-retest (2 weeks apart), whereby 30 unilateral perturbations were executed via the treadmill belts (presets:2.0 m/s amplitude;150 ms delay (post-heel contact);100ms duration). Validity of the perturbations was assessed via mean ± SD comparison, percentage error calculation between the preset and recorded perturbation characteristics (PE%), and coefficient of variation (CV%). Test-retest reliability (TRV%) and Bland-Altman analysis (BLA; bias ± 1.96 * SD) was calculated for reliability. To measure reflex activity, electromyography (EMG) was applied in both legs. EMG amplitudes (root mean square normalized to unperturbed strides) and latencies [ms] were analysed descriptively.

Results

Left-side perturbation amplitude was 1.9 ± 0.1 m/s, delay 105 ± 2 ms, and duration 78 ± 1 ms. Right-side perturbation amplitude was 1.9 ± 0.1 m/s, delay 118 ± 2 ms, duration 78 ± 1 ms. PE% ranged from 5–30% for the recorded perturbations. CV% of the perturbations ranged from 19.5–76.8%. TRV% for the perturbations was 6.4–16.6%. BLA for the left was amplitude: 0.0 ± 0.3m/s, delay: 0 ± 17 ms, duration: 2 ± 13 ms, and for the right was amplitude: 0.1 ± 0.7, delay: 4 ± 40 ms, duration: 1 ± 35 ms. EMG amplitudes ranged from 175 ± 141%–454 ± 359% in both limbs. Latencies were 109 ± 12–116 ± 23 ms in the tibialis anterior, and 128 ± 49-157 ± 20 ms in the biceps femoris.

Discussion

Generally, this study indicated sufficient validity and reliability of the current setup considering the technical challenges and limitations, although the reliability of the right-sided perturbations could be questioned. The protocol provoked reflex responses in the lower extremities, especially in the leading leg. Acute neuromusculoskeletal adjustments to the perturbations could be studied and compared in clinical and healthy running populations, and the protocol could be utilised to monitor chronic adaptations to interventions over time.

Design of an Isometric End-Point Force Control Task for Electromyography Normalization and Muscle Synergy Extraction From the Upper Limb Without Maximum Voluntary Contraction

Muscle synergy analysis via surface electromyography (EMG) is useful to study muscle coordination in motor learning, clinical diagnosis, and neurorehabilitation. However, current methods to extract muscle synergies in the upper limb suffer from two major issues. First, the necessary normalization of EMG signals is performed via maximum voluntary contraction (MVC), which requires maximal isometric force production in each muscle. However, some individuals with motor impairments have difficulties producing maximal effort in the MVC task. In addition, the MVC is known to be highly unreliable, with widely different forces produced in repeated measures. Second, synergy extraction in the upper limb is typically performed with a multidirection reaching task. However, some participants with motor impairments cannot perform this task because it requires precise motor control. In this study, we proposed a new isometric rotating task that does not require precise motor control or large forces. In this task, participants maintain a cursor controlled by the arm end-point force on a target that rotates at a constant angular velocity at a designated force level. To relax constraints on motor control precision, the target is widened and blurred. To obtain a reference EMG value for normalization without requiring maximal effort, we estimated a linear relationship between joint torques and muscle activations. We assessed the reliability of joint torque normalization and synergy extraction in the rotating task in young neurotypical individuals. Compared with normalization with MVC, joint torque normalization allowed reliable EMG normalization at low force levels. In addition, the extraction of synergies was as reliable and more stable than with the multidirection reaching task. The proposed rotating task can, therefore, be used in future motor learning, clinical diagnosis, and neurorehabilitation studies.

Effects of sling exercise therapy on post-stroke walking impairment: a systematic review and meta-analysis

Walking impairment is a common consequence of stroke, resulting in long-term disability. Trunk muscle strength has been proven to be associated with post-stroke walking performance. As a type of trunk training, sling exercise therapy (SET) has been widely used to improve the trunk function in stroke patients. The purpose of this systematic review was to investigate the efficacy of SET on post-stroke walking impairment. Seven databases were systematically searched for eligible studies from their inception to 1 August 2021. Review Manager 5.3 software was used for this meta-analysis. The overall quality of included studies was evaluated by the physiotherapy evidence database scale. Twenty-five randomized controlled trials involving 1504 patients were included (23 in China and two in South Korea). In summary, SET more effectively improved the walking ability of post-stroke patients than conventional physical therapy or trunk training. The pooled analysis demonstrated that SET had positive effects on the 10 m maximum walking speed, integrated electromyography value of rectus femoris, biceps femoris and gastrocnemius, functional ambulation category, timed up and go test, and step length. At least in East Asia, our findings support SET to manage the post-stroke walking impairment.

An International Continence Society (ICS) report on the terminology for pelvic floor muscle assessment

INTRODUCTION

The terminology for female and male pelvic floor muscle (PFM) assessment has expanded considerably since the first PFM function and dysfunction standardization of terminology document in 2005. New terms have entered assessment reports, and new investigations to measure PFM function and dysfunction have been developed. An update of this terminology was required to comprehensively document the terms and their definitions, and to describe the assessment method and interpretation of the finding, to standardize assessment procedures and aid diagnostic decision making.

METHODS

This report combines the input of members of the Standardisation Committee of the International Continence Society (ICS) Working Group 16, with contributions from recognized experts in the field and external referees. A logical, sequential, clinically directed assessment framework was created against which the assessment process was mapped. Within categories and subclassifications, each term was assigned a numeric coding. A transparent process of 12 rounds of full working group and external review was undertaken to exhaustively examine each definition, plus additional extensive internal development, with decision making by collective opinion (consensus).

RESULTS

A Terminology Report for the symptoms, signs, investigations, and diagnoses associated with PFM function and dysfunction, encompassing 185 separate definitions/descriptors, has been developed. It is clinically based with the most common assessment processes defined. Clarity and user-friendliness have been key aims to make it interpretable by clinicians and researchers of different disciplines.

CONCLUSION

A consensus-based Terminology Report for assessment of PFM function and dysfunction has been produced to aid clinical practice and be a stimulus for research.

Inter-Day Reliability and Changes of Surface Electromyography on Two Postural Muscles Throughout 12 Weeks of Hippotherapy on Patients with Cerebral Palsy: A Pilot Study

Cerebral palsy (CP) is an umbrella term covering a group of permanent developmental disorders of movement and posture characterized by highly variable clinical features. The aim of this study was to assess the short-term and mid-term effects of neurorehabilitation via hippotherapy on the contractile properties of two key postural muscles during functional sitting in such patients. Thirty-minute hippotherapy sessions were conducted biweekly for 12 weeks in 18 patients (18.1 ± 5.7 years old). Surface electromyography (EMG) was implemented bilaterally in rectus abdominis and adductor magnus. We quantitatively analyzed the amplitude of EMG signals in the time domain and its spectral characteristics in the frequency domain. EMGs were recorded at the beginning and end of each session on day one and at week six and week twelve. Statistical analysis revealed a substantial inter-day reliability of the EMG signals for both muscles, validating the methodological approach. To a lesser extent, while beyond the scope of the current study, quantitative changes suggested a more selective recruitment/contractile properties’ shift of the examined muscles. Exploring postural control during functional activities would contribute to understanding the relationship between structural impairment, activity performance and patient capabilities, allowing the design of neurorehabilitation programs aimed at improving postural and functional skills according to each individual’s needs. The present study provides basic quantitative data supporting the body of scientific evidence making hippotherapy an approach of choice for CP neurorehabilitation.

Dopamine stimulation of the septum enhances exercise efficiency during complicated treadmill running in mice

We aimed to identify the neurotransmitters and brain regions involved in exercise efficiency in mice during continuous complicated exercises. Male C57BL/6J mice practiced treadmill running with intermittent obstacles on a treadmill for 8 days. Oxygen uptake (VO2) during treadmill running was measured as exercise efficiency. After obstacle exercise training, the VO2 measured during treadmill running with obstacles decreased significantly. Obstacle exercise-induced c-Fos expressions and dopamine turnover (DOPAC/dopamine) in the septum after obstacle exercise training were significantly higher than that before training. The dopamine turnover was correlated with exercise efficiency on the 3rd day after exercise training. Furthermore, the training effect on exercise efficiency was significantly decreased by injection of dopamine receptor antagonists into the septum and was associated with decreased c-Fos expressions in the septum and hippocampus of the mice. These results suggest that dopaminergic function in the septum is involved in exercise efficiency during continuous complicated exercises.

Effects of motor practice on learning a dynamic balance task in healthy young adults: A wavelet-based time-frequency analysis

BACKGROUND

Previous research showed changes in amplitude- or time-derived measures of electromyographic (EMG) activity with motor learning. However, an analysis of the EMG spectral content (e.g., via wavelet technique) has not been included in these investigations yet.

OBJECTIVE

The aim of this study was to use conventional, amplitude-derived EMG parameters along with modern, wavelet-based time-frequency EMG measures to assess the effects of motor practice on learning a dynamic balance task.

METHODS

Nineteen young male adults (mean age: 26 ± 6 years) practiced a dynamic balance task for two days. Delayed retention test was performed on the third day. On a behavioral level, the root-mean-square error (RMSE) of the stability platform angle was calculated and used as outcome measure. On a neuromuscular level, EMG data from the tibialis anterior (TA) and the gastrocnemius medialis (GM) muscle were unilaterally recorded and analysed by calculating the integrated EMG (iEMG) and the EMG intensity (via continuous wavelet transforms).

RESULTS

Two days of practice resulted in significantly improved balance performance (i.e., lower RMSE) and TA/GM activation (i.e., reduced iEMG and EMG intensity) that was still present during the retention test on day 3. There was also evidence of practice-related changes in the EMG intensity pattern as indicated by an intensity shift from higher to lower frequency components.

CONCLUSIONS

We conclude that motor practice leads to improvements in movement effectiveness as indicated by reduced RMSE and in movement efficiency (i.e., decreased iEMG and EMG intensity, intensity shift). In addition to conventional amplitude-derived EMG parameters, modern, wavelet-based time-frequency EMG measures are appropriate to detect practice-related changes in muscle activation.