Isokinetic testing in patients with neuromuscular diseases: a focused review

A Systematic Review of Isokinetic Muscle Strength in a Healthy Population With Special Reference to Age and Gender

CONTEXT

Despite increasing use of reference values in isokinetic measurements and increasing importance, there is no systematic review of the reference values for lower and upper limb isokinetic muscle strength.

OBJECTIVE

A systematic review to analyze studies on the reference values and protocols for the measurement for upper and lower limb isokinetic muscle strength in an untrained and noninjured healthy population.

DATA SOURCES

MEDLINE, Scopus, Scielo, and CINAHL (from the earliest date available to June 2020).

STUDY SELECTION

Studies that measured a set of reference values for isokinetic muscle strength.

STUDY DESIGN

Systematic review.

LEVEL OF EVIDENCE

Level 3.

DATA EXTRACTION

Two reviewers selected studies independently. Data related to participants characteristics, outcomes of interest, isokinetic parameters, reference values for isokinetic muscle strength, and quality of evidence assessment were systematically reviewed independently by 2 authors.

RESULTS

A total of 31 studies met the study criteria. The included studies were used to synthesize the isokinetic muscle strength data according to age-group and sex. We extracted 1845 normative data related to isokinetic strength. Of these, 1181 items referred to lower limbs and 664 items to upper limbs.

CONCLUSION

In general, agonist muscle groups are stronger than antagonist muscles, and the men tend to obtain higher strength values than women. The angular velocity varied from 10 to 300 deg/s. The reference values identified can be useful for professionals to obtain during the isokinetic evaluation of the diagnostic parameters of muscle deficiency.

Instrumented strength assessment in typically developing children and children with a neural or neuromuscular disorder: A reliability, validity and responsiveness study

The aim of this study was to determine the clinimetric properties, i.e., reliability, validity and responsiveness of an instrumented strength assessment in typically developing (TD) children and children with cerebral palsy (CP) and Duchenne muscular dystrophy (DMD). Force (N), torque (Nm) and normalized torque (Nm/kg) were defined for maximal voluntary isometric contractions (MVICs) of the lower limb muscles using a pre-established protocol. Intraclass correlation coefficient (ICC), standard error of measurement (SEM) and minimal detectable change (MDC) of TD children (n = 14), children with CP (n = 11) and DMD (n = 11) were used to evaluate intra-rater reliability for the three cohorts and the inter-rater intersession as well as inter-rater intrasession reliability for TD children. Construct validity was assessed by comparing MVICs in TD children (n = 28) to children with CP (n = 26) and to children with DMD (n = 30), using the Kruskal Wallis and post-hoc Mann-Whitney U tests. Responsiveness was investigated by assessing changes in MVICs following a strength intervention in CP (n = 26) and a 1 and 2 year follow-up study in DMD (n = 13 and n = 6, respectively), using the Wilcoxon Signed-Rank test. The overall intra-rater reliability, was classified as good to excellent for 65.1%, moderate for 27.0% and poor for 7.9% of the measures (47.6%, 76.2%, and 66.7% good-excellent; 28.6%, 23.8%, and 33.7% moderate; 23.8%, 0%, and 0% poor in TD, CP, and DMD, respectively), while ICC values for TD children were slightly lower for inter-rater intrasession reliability (38.1% good-excellent, 33.3% moderate and 26.6% poor) and for inter-rater intersession reliability (47.6% good-excellent, 23.8% moderate and 28.6% poor). Children with CP and DMD were significantly weaker than TD children (p < 0.001) and the majority of these strength differences exceeded the MDC. Children with CP significantly improved strength after training, with changes that exceeded the SEMs, whereas only limited strength decreases over time were observed in the DMD cohort. In conclusion, the investigated instrumented strength assessment was sufficiently reliable to confirm known-group validity for both cohorts and could detect the responsiveness of children with CP after a strength intervention. However, more research is necessary to determine the responsiveness of this assessment in children with DMD regarding their natural decline.

Reliability of Muscle Strength and Muscle Power Assessments Using Isokinetic Dynamometry in Neuromuscular Diseases: A Systematic Review

OBJECTIVE

The purpose of this study was to critically appraise and summarize the evidence for reliability of muscle strength and muscle power assessment in patients with neuromuscular diseases (NMDs) using isokinetic dynamometry.

METHODS

PubMed, CINAHL, and Embase electronic databases were searched from inception to March 8, 2022. Studies designed to evaluate reliability of muscle strength and power measurements using isokinetic dynamometry were included in this review. First, the methodological quality of the studies was assessed according to the Consensus-Based Standards for the Selection of Health Measurement Instruments guidelines. Next, the quality of measurement properties was determined. Finally, the methodological quality and quality of measurement properties of the studies were combined to obtain a best-evidence synthesis.

RESULTS

A best-evidence synthesis of reliability was performed in 11 studies including postpoliomyelitis syndrome (n = 5), hereditary motor and sensory neuropathy (n = 2), motor neuron diseases (n = 1), myotonic dystrophy (n = 1), and groups of pooled NMDs (n = 2). A best-evidence synthesis on measurement error could not be performed. Quality of evidence on reliability ranged from high in postpoliomyelitis syndrome to very low in hereditary motor and sensory neuropathy, motor neuron diseases, and groups of pooled NMDs. The most frequently used outcome measure was peak torque, which was reliable in all populations (intraclass correlation coefficient >0.7).

CONCLUSION

The quality of evidence for reliability of isokinetic dynamometry was found to vary substantially among different NMDs. High quality of evidence has been obtained only in patients with postpoliomyelitis syndrome. Further research is needed in the majority of known NMDs to determine reliability and validity of isokinetic dynamometry.

IMPACT

The ability of isokinetic dynamometers to capture clinically relevant changes in muscle strength and muscle power in NMDs remains unclear. Isokinetic dynamometry results in NMDs should be interpreted with caution.

Practicable performance-based outcome measures of trunk muscle strength and their measurement properties: A systematic review and narrative synthesis

Introduction

The evaluation of muscle strength is frequently used as part of the physical examination process, with decreased trunk muscle strength reported in individuals with spinal disorders (e.g., low back pain). Access to practicable performance-based outcome measures (PBOM) to monitor patients’ progress in spinal rehabilitation is essential. Knowledge of the psychometric properties of the available practicable PBOM for trunk strength evaluation is therefore needed to inform practitioners and further research.

Objective

To synthesise evidence on the measurement properties of practicable measures of trunk muscle strength in adults with and without musculoskeletal pain.

Methods

Following a published and registered protocol [PROSPERO CRD42020167464], databases were searched from the database inception date up to 30th of June 2021. Citations and grey literature were also searched. Eligibility criteria comprised: 1) studies which examined the psychometric properties of the trunk strength outcome measures, 2) included adults ≥ 18 years, either asymptomatic or with spinal musculoskeletal pain. Non-English language studies were excluded. Two independent reviewers evaluated the quality and synthesized the data from included studies according to the COnsensus-based Standards for the selection of health Measurement Instruments (COSMIN) checklist. The overall quality of evidence was evaluated using a modified Grading of Recommendations Assessment Development and Evaluation (GRADE).

Results

From 34 included studies, 15 different PBOMs were identified that have been investigated for reliability and validity, none evaluated responsiveness. In asymptomatic individuals, high quality evidence supports intra-rater reliability of digital-loading cells and moderate quality evidence supports the criterion validity of the hand-held dynamometer. Very low quality evidence exists for the reliability and validity estimates of testing tools among individuals with spinal pain.

Conclusions

Findings underpin a cautious recommendation for the use of practicable PROMs to evaluate muscle strength in individuals with spinal pain in clinical practice due to the level of evidence and the heterogeneity of the protocols used. Further high quality research to explore the psychometric properties of the practicable PBOMs with detailed methodology is now needed.

Measures of trunk muscle strength and their measurement properties: a protocol for a systematic review and narrative synthesis of clinical measures

INTRODUCTION

Spinal musculoskeletal conditions, including low back and neck pain, are leading causes of disability globally. The trunk muscles, which comprise muscles in the thoracic and lumbar regions, are essential for functional activities, necessitating mobility, motor control and strength. To investigate the effectiveness of interventions directed at improving trunk muscle strength, it is essential to have valid, reliable and responsive performance-based outcome measures (PBOM). While isokinetic dynamometry is considered the gold-standard PBOM, the associated costs, size/weight and operational complexity of this equipment preclude its use in a clinical setting. There is, therefore, a need to evaluate the measurement properties of alternative accessible measures of trunk strength. This systematic review therefore aims to investigate the measurement properties of PBOM of trunk muscle strength measures appropriate for use in a clinical setting.

METHODS AND ANALYSIS

This protocol has been designed using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Protocols. CINAHL, Web of Science, Pedro, MEDLINE, EMBASE, SPORTDiscuss will be searched systematically from the database start date up to 16 April 2020, along with reference checking and the grey literature searching. Eligibility criteria include studies investigating measurement properties of PROM for trunk muscle strength for use in a clinical setting in adults with and without spinal musculoskeletal complaints. Two independent reviewers will determine the eligibility of the studies through screening process of titles, abstract and the full text. Both reviewers will assess the risk of bias using COnsensus-based Standards for the selection of health status Measurement Instruments risk-of-bias tool and then extract the data from included studies. The overall quality of the included studies will be evaluated using the Grading of Recommendations Assessment, Development and Evaluation approach. A narrative synthesis will be carried out if meta-analysis is not applicable. Findings from this systematic review will aid clinicians and practitioners working in the field for example, sport, in using the most appropriate PBOM to measure trunk muscle strength.

ETHICS AND DISSEMINATION

No research ethics application is needed as there are no patient data in this study. The results of this study will be submitted to a peer reviewed journal and presented at conferences.

PROSPERO REGISTRATION NUMBER

CRD42020167464.

Measuring the effects of exercise in neuromuscular disorders: a systematic review and meta-analyses

Background: The benefit and safety of exercise training for patients with neuromuscular disorders (NMDs) has long been a contentious topic. This is, in part, due to recognised challenges associated with rare diseases including small and heterogenous patient populations. We performed a systematic review and meta-analyses to evaluate the effectiveness and safety of interventional exercise and establish minimal clinically important differences (MCID) in outcomes to facilitate clinical interpretation. Methods: We searched six databases from inception to Mar 2018. Aerobic, strength, and combined (aerobic and strength) intervention were eligible. Meta-analyses compared outcomes at baseline with those after at least six weeks (before-after exercise within individuals). A further meta-analysis compared outcomes before-after exercise between groups (exercise training versus usual care). Disease heterogeneity was explored using a random effect model. This study was registered (PROSPERO, CRD42018102183). An interactive database was developed to facilitate full interrogations of data. Results: We identified 130 articles describing 1,805 participants with 35 different forms of NMD. Of these studies, 76 were suitable for meta-analyses. Within group and between group meta-analyses detected an increase in peak aerobic capacity (p=0·04), and peak power (p=0·01). Six-minute walk test (p=0·04), sit-to-stand (STS) (repetitions) (p=0·03), STS (seconds) (p=0·04), rise from supine (p=0·008), SF-36 (p=0·0003), fatigue severity (p=<0·0001), citrate synthase (p=0·0002), central nuclei (p=0·04), type 1 (p=0·002) and type II muscle fibre area (p=0·003), were only able to detect change within group meta-analyses. Substantial I 2 statistic heterogeneity was revealed for STS (seconds) ( I²=58·5%; p=0·04) and citrate synthase ( I²=70·90%; p=0·002), otherwise heterogeneity for all outcomes was low. No study-related serious adverse events were reported nor significant increases in creatine kinase. Conclusions: Exercise training in patients with NMDs appears to cause no harm across a range of outcomes. With the emergence of new therapeutic strategies, defining MCID is vital in informing future clinical trial design.

Impact of the EMG normalization method on muscle activation and the antagonist-agonist co-contraction index during active elbow extension: Practical implications for post-stroke subjects

Electromyographic (EMG) raw signals are sensitive to intrinsic and extrinsic factors. Consequently, EMG normalization is required to draw proper interpretations of standardized data. Specific recommendations are needed regarding a relevant EMG normalization method for participants who show atypical EMG patterns, such as post-stroke subjects. This study compared three EMG normalization methods ("isometric MVC", "isokinetic MVC", "isokinetic MVC kinematic-related") on muscle activations and the antagonist-agonist co-contraction index. Fifteen post-stroke subjects and fifteen healthy controls performed active elbow extensions, followed by isometric and isokinetic maximum voluntary contractions (MVC). Muscle activations were obtained by normalizing EMG envelopes during active movement using a reference value determined for each EMG normalization method. The results showed no significant difference between the three EMG normalization methods in post-stroke subjects on muscle activation and the antagonist-agonist co-contraction index. We highlighted that the antagonist-agonist co-contraction index could underestimate the antagonist co-contraction in the presence of atypical EMG patterns. Based on its practicality and feasibility, we recommend the use of isometric MVC as a relevant procedure for EMG normalization in post-stroke subjects. We suggest combined analysis of the antagonist-agonist co-contraction index and agonist and antagonist activations to properly investigate antagonist co-contraction in the presence of atypical EMG patterns during movement.

Isokinetic assessment of trunk muscles in facioscapulohumeral muscular dystrophy type 1 patients

Facioscapulohumeral muscular dystrophy type 1 is the third most common inherited myopathy. Its severity is proportionate to the loss of microsatellite D4Z4 repetitions, which are below 10. Patients suffer from weakness in facial muscles, shoulder girdles and ankle dorsiflexors. Trunk impairment is reported in few studies. To assess correlation between D4Z4 number of repetitions in facioscapulohumeral muscular dystrophy type 1 patients and trunk extensors and flexors isokinetic peak torque, 48 patients with southern Blot confirmed facioscapulohumeral muscular dystrophy type 1 were enrolled to perform clinical evaluation (Ricci's Clinical Severity Scoring, Berg Balance Scale, Functional Reach Test, timed up-and-go test, six-minute walk test, functional independence measure) and trunk isokinetic assessment. Trunk extensors and flexors isokinetic peak torque at 60°/sec were significantly correlated with number of D4Z4 microsatellite repetitions, sex, weight and age-independent (r = 0.391 [0.121; 0.662], p < 0.006 and r = 0.334 [0.028; 0.641], p < 0.033, respectively). Ricci's Clinical Severity Scoring was significantly correlated to trunk extensors isokinetic peak torque at 60°/sec, sex and weight-independent (r = -0.743 [-0.938; -0.548], p < 0.0001). This study demonstrates moderate correlation between pathologic compression of D4Z4 microsatellite array and trunk extensors isokinetic strength among facioscapulohumeral muscular dystrophy type I patients.

Testing a novel isokinetic dynamometer constructed using a 1080 Quantum

This study sought to assess the reliability and comparability of two custom-built isokinetic dynamometers (Model A and Model B) with the gold-standard (Humac Norm). The two custom-built dynamometers consisted of commercially available leg extension machines attached to a robotically controlled resistance device (1080 Quantum), able to measure power, force and velocity outputs. Twenty subjects (14m/6f, 26±4.8yr, 176±7cm, 74.4±12.4kg) performed concentric leg extensions on the custom-built dynamometers and the Humac Norm. Fifteen maximal leg extensions were performed with each leg at 180° s^-1, or the linear equivalent (~0.5m s^-1). Peak power (W), mean power (W), and fatigue indexes (%) achieved on all three devices were compared. Both custom-built dynamometers revealed high reliability for peak and mean power on repeated tests (ICC>0.88). Coefficient of variation (CV) and standard error of measurement (SEM) were small when comparing power outputs obtained using Model A and the Humac Norm (x¯ CV = 9.0%, x¯ SEM = 49W; peak CV = 8.4%, peak SEM = 49W). Whereas, Model B had greater variance (x¯ CV = 13.3% x¯ SEM = 120W; peak CV = 14.7%, peak SEM = 146W). The custom-built dynamometers are capable of highly reliable measures, but absolute power outputs varied depending on the leg extension model. Consistent use of a single model offers reliable results for tracking muscular performance over time or testing an intervention.

Effect of Gender, Disease Duration and Treatment on Muscle Strength in Myasthenia Gravis

INTRODUCTION

The aim of this observational, cross-sectional study was to quantify the potential presence of muscle weakness among patients with generalized myasthenia gravis (gMG). The influence of gender, treatment intensity and disease duration on muscle strength and disease progression was also assessed.

METHODS

Muscle strength was tested in 8 muscle groups by manual muscle testing and by hand-held dynamometry in 107 patients with gMG and 89 healthy age- and gender-matched controls. Disease duration, severity and treatment history were reviewed and compared with muscle strength.

RESULTS

Patients had reduced strength in all tested muscle group compared to control subjects (p<0.05). Women with gMG were stronger than men (decrease in strength 22.6% vs. 32.7% in men, P<0.05). Regional differences in muscle weakness were also evident, with proximal muscles being more affected. Interestingly, muscle strength did not correlate with disease duration and treatment intensity.

CONCLUSIONS

The results of this study show that in patients with gMG; 1) there is significant muscle weakness, 2) muscle weakness is more pronounced in men than women, 3) shoulder abductors, hip flexors, and neck muscles are the most affected muscle groups and 4) disease duration or treatment intensity alone are not predictors of loss of muscle strength in gMG.

Novel methods of inspiratory muscle training via the Test of Incremental Respiratory Endurance (TIRE)

The favorable effects of inspiratory muscle training (IMT) in health and disease are becoming much more apparent. A variety of IMT methods exist, but few studies have compared IMT methods. The purpose of this article is to review the methods and outcomes of the Test of Incremental Respiratory Endurance (TIRE).

Differences in muscle strength in parkinsonian patients affected on the right and left side

Background

Muscular weakness is a frequent cause of instability that contributes to falls in Parkinson’s disease (PD). Isokinetic dynamometry is a method of muscle assessment useful to measure the muscular strength giving a quantification of the weakness, but only few studies about isokinetic assessment were performed in PD. The aims of the study were to evaluate the muscle strength in PD and to investigate the differences in patients affected on the right and left side.

Methods

Knee flexor and extensor muscles strength was assessed using an isokinetic dynamometer in 25 patients in stage 3 H&Y and in 15 healthy controls. Subjects were tested in both legs at three fixed angular velocities: 90°/s, 120°/s, 180°/s.

Results

Considering the whole population of Parkinsonians, no difference in strength was observed with respect to controls. Considering the side, patients affected on the right side showed a clear tendency to be weaker than patients affected on the left side and controls.

Conclusions

PD patients affected on the right side, but not those affected on the left side, had a reduction in muscle strength as compared to controls. We postulate a central origin deficit in muscle strength in PD. It is known that dopamine transporter binding is more severely reduced in the left posterior putamen and our results suggest that the control of the muscle strength in PD is linked to the right–left hemispheric asymmetry of the functional organization of basal ganglia and with their connections to cortical motor and pre-motor areas.

Impact of exercise-induced fatigue on the strength, postural control, and gait of children with a neuromuscular disease

OBJECTIVE

Children with a neuromuscular disease are prone to early muscular fatigue. The objective of the present study was to evaluate the effects of fatigue induced by a walking exercise on the strength, postural control, and gait of children with a neuromuscular disease.

DESIGN

Maximal isometric knee strength (extension and flexion), quiet standing postural control, and gait were evaluated in 12 children (8.8 [1.4] yrs) with a neuromuscular disease before and after a walking exercise. The participants were asked to stop walking when they considered themselves "very fatigued."

RESULTS

After the exercise-induced fatigue, a significant increase in range of motion in pelvis obliquity, hip abduction and adduction, and ankle flexion and extension during gait was reported along with an increase in stride length variability. Fatigue also reduced the knee flexor strength and had a detrimental effect on postural control.

CONCLUSIONS

Fatigue affects the strength, postural control, and gait of children with a neuromuscular disease and could notably increase the risks of falling and the occurrence of serious injuries.