Reproducibility of maximal quadriceps strength and its relationship to maximal voluntary activation in postpoliomyelitis syndrome11No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the author(s) or upon any organization with which the author(s) is/are associated

Two-year course of walking adaptability in persons living with late effects of polio

OBJECTIVE

To evaluate the 2-year course of walking adaptability in persons with late effects of polio.

DESIGN

Prospective cohort study.

PATIENTS

A total of 48 persons with late effects of polio (69% female, mean age 63.1 years) with a fall history and/or fear of falling.

METHODS

Walking adaptability (i.e. variable target-stepping and reactive obstacle-avoidance) was assessed on an interactive treadmill at baseline, 1 year and 2 years. Further, leg-muscle strength and balance were assessed at baseline. The course of walking adaptability was analysed with linear mixed models. Based on median values, subgroups were defined for low vs high baseline walking-adaptability and for clinical characteristics. Tme by subgroup interactions were analysed.

RESULTS

Variable target-stepping and reactive obstacle-avoidance did not change (p > 0.285). Reactive obstacle-avoidance improved for persons with a high balance score at baseline (p = 0.037), but not for those with lower scores (p = 0.531). No other time by subgroup interactions were found (p > 0.126).

CONCLUSION

Walking adaptability did not change in persons with late effects of polio over 2 years, and walking adaptability course did not differ between subgroups stratified for walking adaptability determinants, except for balance. Since falls are a major problem among persons with late effects of polio, future studies should investigate whether walking adaptability declines over a longer time and which persons are most at risk.

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.

The relationship between quantitative magnetic resonance imaging of the ankle plantar flexors, muscle function during walking and maximal strength in people with neuromuscular diseases

BACKGROUND

Progression of plantar flexor weakness in neuromuscular diseases is usually monitored by muscle strength measurements, although they poorly relate to muscle function during walking. Pathophysiological changes such as intramuscular adipose tissue affect dynamic muscle function independent from isometric strength. Diffusion tensor imaging and T2 imaging are quantitative MRI measures reflecting muscular pathophysiological changes, and are therefore potential biomarkers to monitor plantar flexor functioning during walking in people with neuromuscular diseases.

METHODS

In fourteen individuals with plantar flexor weakness diffusion tensor imaging and T2 scans of the plantar flexors were obtained, and the diffusion indices fractional anisotropy and mean diffusivity calculated. With a dynamometer, maximal isometric plantar flexor strength was measured. 3D gait analysis was used to assess maximal ankle moment and power during walking.

FINDINGS

Fractional anisotropy, mean diffusivity and T2 relaxation time all moderately correlated with maximal plantar flexor strength (r > 0.512). Fractional anisotropy and mean diffusivity were not related with ankle moment or power (r < 0.288). T2 relaxation time was strongly related to ankle moment (r = -0.789) and ankle power (r = -0.798), and moderately related to maximal plantar flexor strength (r < 0.600).

INTERPRETATION

In conclusion, T2 relaxation time, indicative of multiple pathophysiological changes, was strongly related to plantar flexor function during walking, while fractional anisotropy and mean diffusivity, indicative of fiber size, only related to maximal plantar flexor strength. This indicates that these measures may be suitable to monitor muscle function and gain insights into the pathophysiological changes underlying a poor plantar flexor functioning during gait in people with neuromuscular diseases.

CORP: Measurement of upper and lower limb muscle strength and voluntary activation

Muscle strength, the maximal force-generating capacity of a muscle or group of muscles, is regularly assessed in physiological experiments and clinical trials. An understanding of the expected variation in strength and the factors that contribute to this variation is important when designing experiments, describing methodologies, interpreting results, and attempting to replicate methods of others and reproduce their findings. In this review (Cores of Reproducibility in Physiology), we report on the intra- and inter-rater reliability of tests of upper and lower limb muscle strength and voluntary activation in humans. Isometric, isokinetic, and isoinertial strength exhibit good intra-rater reliability in most samples (correlation coefficients ≥0.90). However, some tests of isoinertial strength exhibit systematic bias that is not resolved by familiarization. With the exception of grip strength, few attempts have been made to examine inter-rater reliability of tests of muscle strength. The acute factors most likely to affect muscle strength and serve as a source of its variation from trial-to-trial or day-to-day include attentional focus, breathing technique, remote muscle contractions, rest periods, temperature (core, muscle), time of day, visual feedback, body and limb posture, body stabilization, acute caffeine consumption, dehydration, pain, fatigue from preceding exercise, and static stretching >60 s. Voluntary activation, the nervous system’s ability to drive a muscle to create its maximal force, exhibits good intra-rater reliability when examined with twitch interpolation (correlation coefficients >0.80). However, inter-rater reliability has not been formally examined. The methodological factors most likely to influence voluntary activation are myograph compliance and sensitivity; stimulation location, intensity, and inadvertent stimulation of antagonists; joint angle (muscle length); and the resting twitch.

Whole Body Vibration Methods with Survivors of Polio

The purpose of the original study was to examine the use of whole body vibration (WBV) on polio survivors with and without post-polio syndrome as a form of weight bearing exercise. The goal of this article is to highlight the strengths, limitations, and applications of the method used. Fifteen participants completed two intervention blocks with a wash-out period in between the blocks. Each block consisted of twice a week (four weeks) WBV interventions, progressing from 10 to 20 min per session. Low intensity (peak to peak displacement 4.53 mm, frequency 24 Hz, g force 2.21) and higher intensity (peak to peak displacement 8.82 mm, frequency 35 Hz, g force 2.76) WBV blocks were used. Pain severity significantly improved in both groups following higher intensity vibration. Walking speed significantly improved in the group who participated in higher intensity intervention first. No study-related adverse events occurred. Even though this population can be at risk of developing overuse-related muscle weakness, fatigue, or pain from excessive physical activity or exercise, the vibration intensity levels utilized did not cause significant muscle weakness, pain, fatigue, or sleep disturbances. Therefore, WBV appears to provide a safe method of weight bearing exercise for this population. Limitations included the lack of measurement of reflexes, muscular activity, or circulation, the difficulty in participant recruitment, and insufficient strength of some participants to stand in recommended position. Strengths included a standard, safe protocol with intentional monitoring of symptoms and the heterogeneity of the participants in their physical abilities. An application of the methods is the home use of WBV to reduce the barriers associated with going to a facility for weight bearing exercise for longer term interventions, and benefits for conditions such as osteoporosis, particularly for aging adults with mobility difficulties due to paralysis or weakness. Presented method may serve as a starting point in future studies.

Whole body vibration on people with sequelae of polio

PURPOSE

The purpose was to explore the feasibility of whole body vibration (WBV) on polio survivors with/without post-polio syndrome (PPS) by studying its effects on walking speed (10-m walk test), endurance (2-min walk test), pain severity/interference (Brief Pain Inventory [BPI]), sleep quality (Pittsburg Sleep Quality Index), fatigue (Fatigue Severity Scale), leg strength (manual muscle testing and hand-held dynamometry), and muscle cramping (written logs).

METHODS

Fifteen individuals completed the study, participating in eight sessions in two 4-week blocks. Participants started with ten 1-min vibration bouts/session, increasing to 20 min. Low (amplitude 4.53 mm, g force 2.21) and higher (amplitude 8.82 mm, g force 2.76) intensity blocked intervention occurred in random order crossover design. Blinded testing ensued before/after intervention blocks and at follow-up.

RESULTS

No study-related adverse events occurred. Participants starting first with higher intensity intervention improved in walking speed (p = 0.017). BPI pain severity significantly improved (p = 0.049) after higher intensity intervention. No significant changes were found after low intensity vibration or in other outcome measures.

CONCLUSIONS

WBV appears to be a safe exercise for this population. Long-term use in polio survivors needs to be researched, particularly in reducing barriers to participation to promote the physical aspects of health.

Comparison of quadriceps inactivation between nerve and muscle stimulation

We evaluated the use of direct muscle stimulation for quantifying quadriceps inactivation at different contraction levels as opposed to conventional twitch interpolation using nerve stimulation. Fourteen healthy volunteers were tested. Paired stimuli were delivered to the femoral nerve or to the quadriceps muscle belly during voluntary contractions ranging from 20% to 100% of maximum, and the amplitude of the superimposed doublet was quantified to investigate inactivation. Superimposed doublet for muscle and nerve stimulation, respectively between the range of 60% to 100% of maximum (e.g., at 100%, muscle stimulation was 14 ± 5 Nm and nerve stimulation was 15 ± 6 Nm). Despite higher current doses, muscle stimulation was associated with less discomfort than nerve stimulation (P < 0.05). Collectively, our data suggest that direct muscle stimulation could be used to assess quadriceps inactivation at maximal and quasi-maximal contraction levels as a valid alternative to motor nerve stimulation.

Reliability and performance-dependent variations of muscle function variables during isometric knee extension

Despite the common use of standardised methods analysing neuromuscular function during knee extension, there is a lack of test-retest reliability studies. Furthermore, for most of the investigated variables it is unknown which changes of values indicate an enhancement of performance. The aim of the present study was to investigate performance-dependent variations of muscle functions during isometric contraction of knee extensors and to examine test-retest reliability of their measurement methods. For test-retest reliability sports students completed three test sessions. Highly skilled athletes, sports students and untrained subjects were investigated to determine the performance-dependent variations. The following variables were analysed: maximal voluntary contraction (MVC), voluntary activation (VA), absolute muscle reaction time (AR), muscle endurance (ME), and EMG frequency analysis (MF) of m. vastus lateralis (VL), m. vastus medialis (VM) and m. rectus femoris (RF). RESULTS TEST-RETEST-RELIABILITY: A high reliability between session 1 vs. 2 and session 2 vs. 3 was shown for MVC (ICC=0.92 and .97), VA (0.92/0.95) and ME (0.87/0.95). ICC in AR (0.23) was low between the first and second session and moderate between the second and third session (0.74). MF of VL, VM and RF showed low ICC between sessions. PERFORMANCE DEPENDENT VARIATIONS: Significant differences in nearly all variables (except VA) were found between trained (athletes and sports students) and untrained subjects.

Fatigue and neuromuscular diseases

PURPOSE

To identify the role of fatigue, its evaluation and its causes in the pathophysiology context of acquired or hereditary neuromuscular diseases of the spinal anterior horn cell, peripheral nerve, neuromuscular junction and muscle.

MATERIAL AND METHODS

A literature review has been done on Medline with the following keywords: neuromuscular disease, peripheral neuropathy, myopathy, fatigue assessment, exercise intolerance, force assessment, fatigue scale and questionnaire, then with the terms: Fatigue Severity Scale, Chalder Fatigue Scale, Fatigue Questionnaire, Piper Fatigue Scale, electromyography and the combination of the word Fatigue with the following terms: Amyotrophic Lateral Sclerosis (ALS), Post-Polio Syndrome (PPS), Guillain-Barre Syndrome, Immune Neuropathy, Charcot-Marie-Tooth Disease, Myasthenia Gravis (MG), Metabolic Myopathy, Mitochondrial Myopathy, Muscular Dystrophy, Facioscapulohumeral Dystrophy, Myotonic Dystrophy.

RESULTS

Fatigue is a symptom very frequently reported by patients. Fatigue is mainly evaluated by strength loss after an exercise, by change in electromyographic activity during a given exercise and by questionnaires that takes into account the subjective (psychological) part of fatigue. Due to the large diversity of motor disorders, there are multiple clinical expressions of fatigue that differ in their presentation, consequences and therapeutic approach.

CONCLUSION

This review shows that fatigue has to be taken into account in patients with neuromuscular diseases. In this context, pathophysiology of fatigue often implies the motor component but the disease evolution and the physical obligates of daily life also induce an important psychological component.