Grip strength is a representative measure of muscle weakness in the upper extremity after stroke

Background: Muscle weakness is the most common impairment in the upper extremity after stroke, leading to a reduced ability to use the arm and the hand in daily activities. Grip strength is easier to measure than precise, but more time-consuming, isokinetic and isometric arm muscle strength measurements. It would therefore be advantageous in a clinical setting if grip strength could be used as a proxy for muscle strength in the entire upper extremity.

Objective: To investigate the association between grip strength and isometric and isokinetic arm muscle strength in persons with chronic stroke.

Methods: Forty-five persons with mild-to-moderate paresis in the upper extremity, at least 6 months post-stroke participated. Isometric grip strength was measured with a computerized grip dynamometer and arm strength (isometric shoulder abduction and elbow flexion as well as isokinetic elbow extension and flexion) with an isokinetic dynamometer. Pearson’s correlation coefficient was used to determine the association between the muscle strength measurements.

Results: There were significant correlations (p < .0001) between grip strength and all arm strength measurements in both the more affected (r = 0.77–0.82) and the less affected upper extremity (r = 0.65–0.82).

Conclusion: This cross-sectional study showed that grip strength is strongly associated with muscle strength in the arm in persons in the chronic phase after stroke. As grip strength is easy to measure and less time-consuming than arm muscle strength measurements, this implies that grip strength can be a representative measure of muscle weakness of the entire upper extremity in the chronic phase after stroke.     

Modeling functional decline over time in sporadic inclusion body myositis

Introduction: The ability to individualize recommendations or expectations of disease progression based on a patient's unique characteristics has merit for use in sporadic inclusion body myositis (sIBM). Methods: Fifty‐five subjects with sIBM completed a battery of strength and functional outcomes at 2 study visits. These were used to develop mathematical models of disease progression in patients with sIBM for use in clinical and research settings. Results: The 6‐minute walk test (6MWT) distance declined by an average of 27.5 meters (12%) per year. Significant factors that predict 6MWT were knee extension and plantarflexion strength and body weight, whereas the ability to stand from a chair was impacted by elbow extension strength. Stepping up on a curb was influenced by the patient's age at diagnosis and by knee extension. Statistical models to predict functional decline in sIBM were developed. Conclusion: Statistical models help explain the complex factors that influence decreased walking ability and other functional activities in sIBM. Muscle Nerve 55 : 526–531, 2017     

Identification of dynapenia in older adults through the use of grip strength t‐scores

Introduction: The aim of this study was to generate reference values and t‐scores (1.0–2.5 standard deviations below average) for grip strength for healthy young adults and to examine the utility of t‐scores from this group for the identification of dynapenia in older adults. Methods: Our investigation was a population‐based, general community secondary analysis of cross‐sectional grip strength data utilizing the NIH Toolbox Assessment norming sample. Participants consisted of community‐dwelling adults, with age ranges of 20–40 years (n = 558) and 60–85 years (n = 390). The main outcome measure was grip strength using a Jamar plus dynamometer. Results: Maximum grip strengths were consistent over the 20–40‐year age group [men 108.0 (SD 22.6) pounds, women 65.8 (SD 14.6) pounds]. Comparison of older group grip strengths to those of the younger reference group revealed (depending on age strata) that 46.2–87.1% of older men and 50.0–82.4% of older women could be designated as dynapenic on the basis of t‐scores. Conclusions: The use of reference value t‐scores from younger adults is a promising method for determining dynapenia in older adults. Muscle Nerve 51 : 102–105, 2015     

Effect of hip and knee position on nerve conduction in the common fibular nerve

Introduction: The aim of this study was to measure the influence that hip and knee position have on routine fibular motor nerve conduction studies. Methods: Healthy subjects under age 40 were recruited (n = 24) to have fibular nerve conduction studies completed in various positions, using hip extension‐knee extension as a control. Results: A mean increase in conduction velocity of 2.5 m/s across the knee (P = 0.020) was seen during hip flexion compared with hip extension. A mean decrease in velocity of 1.6 m/s through the leg segment (P = 0.016) was seen during knee flexion compared with knee extension. Conclusions: This study shows that the optimal position of the leg during fibular nerve studies is with the hip in flexion and knee in extension, to more accurately reflect nerve length for velocity calculations. This may have implications for other peripheral nerves with respect to proximal joint position affecting calculated velocity. Muscle Nerve 56 : 519–521, 2017     

Quadriceps strength is a sensitive marker of disease progression in sporadic inclusion body myositis

There are currently no effective treatments to restore the muscle function in sporadic inclusion body myositis. Natural history studies of this disease are scarce. The goal of this study consisted in defining the functional pattern of patients with sporadic inclusion body myositis and to follow its change over a 9-month period to determine the most sensitive outcome measures for future clinical trials. Twenty-two patients with definite sporadic inclusion body myositis were assessed using clinical and functional scales. Dynamometry was used to evaluate the strength for hand grip and wrist, elbow, ankle and knee flexion and extension. Among the patients, 16 were reassessed 9 months later. The mean whole composite index was at 43.3 ± 16.5% of the predicted normal values. The weakest muscle functions were hand grip, wrist flexion and elbow flexion at the upper limbs and knee extension and ankle flexion at the lower limbs. Muscle weakness was generally asymmetrical, especially for upper limbs where all tested functions were significantly stronger at the dominant side. The patient strength was correlated with the disease duration only for knee extension, which was also the only muscle function to change significantly over 9 months. Knee extension strength seems to be the most relevant marker of disease progression in sporadic inclusion body myositis when measured with suitable dynamometry.     

Body weight‐supported training in Becker and limb girdle 2I muscular dystrophy

Introduction: We studied the functional effects of combined strength and aerobic anti‐gravity training in severely affected patients with Becker and Limb‐Girdle muscular dystrophies. Methods: Eight patients performed 10‐week progressive combined strength (squats, calf raises, lunges) and aerobic (walk/run, jogging in place or high knee‐lift) training 3 times/week in a lower‐body positive pressure environment. Closed‐kinetic‐chain leg muscle strength, isometric knee strength, rate of force development (RFD), and reaction time were evaluated. Results: Baseline data indicated an intact neural activation pattern but showed compromised muscle contractile properties. Training (compliance 91%) improved functional leg muscle strength. Squat series performance increased 30%, calf raises 45%, and lunges 23%. Conclusions: Anti‐gravity training improved closed‐kinetic‐chain leg muscle strength despite no changes in isometric knee extension strength and absolute RFD. The improved closed‐kinetic‐chain performance may relate to neural adaptation involving motor learning and/or improved muscle strength of other muscles than the weak knee extensors. Muscle Nerve 54 : 239–243, 2016     

Muscle architecture and strength: Adaptations to short‐term resistance training in older adults

Introduction: Muscle morphology and architecture changes in response to 6 weeks of progressive resistance training were examined in healthy older adults. Methods: In this randomized, controlled design, muscle strength, quality, and architecture were evaluated with knee extension, DEXA, and ultrasound, respectively, in 25 older adults. Results: Resistance training resulted in significant increases in strength and muscle quality of 32% and 31%, respectively. Cross‐sectional area of the vastus lateralis increased by 7.4% (p ≤ 0.05). Physiological cross‐sectional area (PCSA) of the thigh, a composite measure of muscle architecture, was related significantly to strength (r = 0.57; p ≤ 0.01) and demonstrated a significant interaction after training (p ≤ 0.05). Change in PCSA of the vastus lateralis was associated with change in strength independent of any other measure. Conclusions: Six weeks of resistance training was effective at increasing strength, muscle quality, and muscle morphology in older adult men and women. Muscle Nerve 49:584–592, 2014     

Clinical trial readiness in non‐ambulatory boys and men with duchenne muscular dystrophy: MDA–DMD network follow‐up

Introduction: Outcomes sensitive to change over time in non‐ambulatory boys/men with Duchenne muscular dystrophy (DMD) are not well‐established. Methods: Subjects (n = 91; 16.8 ± 4.5 years old) were assessed at baseline and 6‐month intervals for 2 years. We analyzed all subjects using an intent‐to‐treat model and a subset of stronger subjects with Brooke Scale score ≤4, using repeated measures. Results: Eight patients (12–33 years old) died during the study. Sixty‐six completed 12‐month follow‐up, and 51 completed 24‐month follow‐up. Those taking corticosteroids performed better at baseline, but rates of decline were similar. Forced vital capacity percent predicted (FVC% predicted) declined significantly only after 2 years. However, Brooke and Egen Klassifikation (EK) Scale scores, elbow flexion, and grip strength declined significantly over both 1 and 2 years. Conclusion: Brooke and EK Scale scores, elbow flexion, and grip strength were outcomes most responsive to change. FVC% predicted was responsive to change over 2 years. Corticosteroids benefited non‐ambulatory DMD subjects but did not affect decline rates of measures tested here. Muscle Nerve 54 : 681–689, 2016     

Axonal excitability during ischemia in MELAS

Introduction: We investigated muscle activation strategy and performance of knee extensor and flexor muscles in children and adults with generalized joint hypermobility (GJH) and compared them with controls. Methods: Muscle activation, torque steadiness, electromechanical delay, and muscle strength were evaluated in 39 children and 36 adults during isometric knee extension and flexion. Subjects performed isometric maximum contractions, submaximal contractions at 25% maximum voluntary contraction (MVC), and explosive contractions. Results: Agonist activation was reduced, and coactivation ratio was greater in GJH during knee flexion compared with controls. Torque steadiness was impaired in adults with GJH during knee flexion. No effect of GJH was found on muscle strength or electromechanical delay. Correlation analysis revealed an association between GJH severity and function in adults. Conclusions: The results indicate that muscle activation strategy and quality of force control were significantly affected in adults with GJH during knee flexion, whereas only muscle activation strategy was affected in children with GJH. Muscle Nerve 48:762–769, 2013     

Quantitative and qualitative adaptations of muscle fibers to glucocorticoids

Introduction: The aim of this study was to understand the effects of short‐term glucocorticoid administration in healthy subjects. Methods: Five healthy men received dexamethasone (8 mg/day) for 7 days. Vastus lateralis muscle biopsy and knee extension torque measurement were performed before and after administration. A large number of individual muscle fibers were dissected from the biopsy samples (pre‐administration: n = 165, post‐administration: n = 177). Results: Maximal knee extension torque increased after administration (～13%), whereas both type 1 and type 2A fibers had decreased cross‐sectional area (type 1: ～11%, type 2A: ～17%), myosin loss (type 1: ～18%, type 2A: ～32%), and loss of specific force (type 1: ～24%, type 2A: ～33%), which were preferential for fast fibers. Conclusion: Short‐term dexamethasone administration in healthy subjects elicits quantitative and qualitative adaptations of muscle fibers that precede (and may predict) the clinical appearance of myopathy in glucocorticoid‐treated subjects. Muscle Nerve 52: 631–639, 2015     

Developing normalized strength scores for neuromuscular research

Introduction: The Accurate Test of Limb Isometric Strength (ATLIS) device can reliably measure the strength of 12 muscle groups using a fixed load cell. The purpose of this study was to analyze ATLIS data from healthy adults to calculate an individual's predicted strength scores. Methods: ATLIS data were collected from 432 healthy adults. Linear regression models were developed to predict each muscle group's strength. The R‐squared statistic assessed variability accounted for by the models. Results: Simple main effects models stratified by gender were used to establish regression equations for each muscle using factors of age, weight, and height. Conclusions: Normalizing raw strength scores controls for biometric factors, thus enabling meaningful comparisons between subjects and allowing each muscle to contribute equally to a summary score. Normalized scores are easily interpreted for broad clinical uses, and derived summary scores establish individuals' disease progression rates using a common scale, allowing for more efficient clinical trials. Muscle Nerve, 2013     

Resistance training and aerobic training improve muscle strength and aerobic capacity in chronic inflammatory demyelinating polyneuropathy

Introduction: We investigated the effects of aerobic and resistance exercise in patients with chronic inflammatory demyelinating polyneuropathy (CIDP). Methods: Eighteen CIDP patients treated with subcutaneous immunoglobulin performed 12 weeks of aerobic exercise and 12 weeks of resistance exercise after a run‐in period of 12 weeks without exercise. Three times weekly the participants performed aerobic exercise on an ergometer bike or resistance exercise with unilateral training of knee and elbow flexion/extension. Primary outcomes were maximal oxygen consumption velocity (VO₂‐max) and maximal combined isokinetic muscle strength (cIKS) of knee and elbow flexion/extension. Results: VO₂‐max and muscle strength were unchanged during run‐in (?4.9% ± 10.3%, P = 0.80 and ?3.7% ± 10.1%, P = 0.17, respectively). Aerobic exercise increased VO₂‐max by 11.0% ± 14.7% (P = 0.02). Resistance exercise resulted in an increase of 13.8% ± 16.0% (P = 0.0004) in cIKS. Discussion: Aerobic exercise training and resistance exercise training improve fitness and strength in CIDP patients. Muscle Nerve 57 : 70–76, 2018     

Inverse activation between the deeper vastus intermedius and superficial muscles in the quadriceps during dynamic knee extensions

Introduction: We sought to determine the neuromuscular activation patterns of 4 synergistic muscles of the quadriceps femoris (QF), including the vastus intermedius (VI) muscle, during dynamic knee extensions. Methods: Nine healthy men performed dynamic knee extensions in the range of 20–100% of the one‐repetition maximum (1RM) load. Surface electromyography (EMG) was recorded from the 4 muscles of the QF. Results: The normalized EMG amplitude of the VI was significantly higher at knee joint angles between 90° and 115° during both the concentric and eccentric phases, and it was significantly lower between 140° and 165° during concentric and eccentric phases, compared with those of vastus lateralis at 60–100% of 1RM load (P < 0.05). Conclusions: These results suggest that the VI plays a key role during dynamic knee extension with flexed joint angles and specifically contributes to the initial concentric and final eccentric phases of knee joint movements. Muscle Nerve 47: 682–690, 2013     

Maximal isometric muscle strength values obtained By hand‐held dynamometry in children between 6 and 15 years of age

Introduction: In this study we aimed to determine the maximal isometric muscle strength of a healthy, normal‐weight, pediatric population between 6 and 15 years of age using hand‐held dynamometry to establish strength reference values. The secondary objective was determining the relationship between strength and anthropometric parameters. Methods: Four hundred normal‐weight Chilean children, split into 10 age groups, separated by 1‐year intervals, were evaluated. Each age group included between 35 and 55 children. Results: The strength values increased with increasing age and weight, with a correlation of 0.83 for age and 0.82 for weight. The results were similar to those reported in previous studies regarding the relationships among strength, age, and anthropometric parameters, but the reported strength differed. Conclusions: These results provide normal strength parameters for healthy and normal‐weight Chilean children between 6 and 15 years of age and highlight the relevance of ethnicity in defining reference values for muscle strength in a pediatric population. Muscle Nerve 55 : 16–22, 2017     

Diurnal and day‐to‐day variation of isometric muscle strength in myasthenia gravis

Introduction: In patients with myasthenia gravis (MG), muscle strength is expected to decrease gradually during the day due to physical activities. Methods: Isometric muscle strength at the shoulder, knee, and ankle was determined in 10 MG patients (MGFA class II–IV) who were receiving usual medical treatment and in 10 control subjects. To determine diurnal and day‐to‐day variation, muscle strength was measured 4 times during day 1 and once at day 2. Results: Knee extension strength decreased during the day in both patients and controls. Neither diurnal nor day‐to‐day variation of muscle strength was higher in patients compared with controls. Conclusions: Patients with mild to moderate MG did not have increased variation of isometric muscle strength during the day or from day‐to‐day compared with controls. This suggests that isometric muscle performance can be determined with high reproducibility in similar groups of MG patients without regard to time of day. Muscle Nerve 53 : 67–72, 2016     

Is gamma loop dysfunction related to bilateral inhibition in anterior knee pain?

Introduction: The potential relationship between bilateral quadriceps inhibition in individuals with unilateral anterior knee pain (AKP) and gamma loop dysfunction is examined in this study. Methods: Twelve individuals with unilateral AKP and 10 healthy controls were recruited. Quadriceps voluntary activation (%VA) was quantified using a triggered interpolated twitch technique. Gamma loop function was assessed through knee extension maximum voluntary isometric contractions before and after 20 minutes of 50‐Hz patellar tendon vibration. Results: The AKP group exhibited 5.7% lower %VA bilaterally compared with controls (P = 0.039, Cohen d = 0.79). After prolonged vibration, both groups exhibited an average 8.5% reduction in knee extension force in each limb (P < 0.001, Cohen d = 0.85). Conclusions: Significant force reductions after vibration suggest that gamma loop dysfunction was not seen in either control or AKP participants. Bilateral quadriceps inhibition in the AKP group does not appear to be associated with gamma loop dysfunction. Muscle Nerve 53: 280–286, 2016     

Muscle weakness and functional disability in patients with myasthenia gravis

Introduction: Muscle weakness and functional disability have not been evaluated in a population-based study of patients with myasthenia gravis (MG). Methods: All patients with MG in a well-defined catchment area were identified in the Danish National Patient Registry. Of the 175 eligible patients, 90 participated and were studied using MG-specific scales, isometric dynamometry, and functional tests. Fifty age- and sex-matched subjects served as controls. Results: Muscle strength was reduced by 13%, 21%, and 12% for shoulder abduction, knee extension, and ankle extension, respectively (P < 0.05). Chair stand and 400-meter walking were impaired by 24% and 23%, respectively (P < 0.05). Muscle strength and functional performances were related to MG-specific scales. Discussion: MG patients have moderately reduced isometric muscle strength and impaired physical performance. Muscle weakness and functional tests relate closely to MG-specific scales, suggesting that dynamometry and functional tests can be used to monitor MG patients and as efficacy parameters in clinical trials. Muscle Nerve 59 :218–223, 2019     

健康儿童膝关节屈伸工作时的生物力学规律*

背景：在等速肌力测试的人群中，关于儿童的等速肌力测试研究报道较少。 目的：通过对儿童膝关节屈伸肌力情况的测试，探讨儿童膝关节屈伸工作时的生物力学规律。 设计、时间及地点：对比观察，于2006-10-12在河北师范大学体育学院实验室进行测试。 对象：志愿受试的健康儿童选自石家庄市部分小学10岁左右的学生66名，男31名，女35名。 方法：运用澳大利亚Kylingk公司生产的“Kinitech”等速肌力测试系统进行等速肌力测试，采用60，120，240 (°)/s 3种速度测试儿童膝关节屈伸肌力。 主要观察指标：男女儿童屈伸肌峰力矩值比较和最大功率比较。 结果：①3种不同测试速度中，男女儿童膝关节屈伸肌峰力矩值呈现随测试速度的增加而下降，最大功率随测试速度的增加而增加的趋势。儿童左侧峰力矩值大于右侧。③男女儿童各自屈伸肌峰力矩值均值比值F/E > 0.7，并且随测试速度的增加而增大。④在60，120 (°)/s的测试中, 膝关节屈肌和伸肌峰力矩值性别差异无显著性意义（P > 0.05），240 (°)/s测试中左右侧屈肌峰力矩值性别差异具有显著性意义（P < 0.01，P < 0.05），男生左侧伸肌峰力矩值大于女生（P < 0.05）。 结论：儿童在不同的测试速度中，峰力矩及最大功率表现出的变化趋势与成人一致。提示儿童早期参加体育活动时应注意发展屈肌力量，使屈伸肌力量平衡发展。     

Assessment of intensive care unit‐acquired weakness in young and old mice: An E. coli septic peritonitis model

Introduction: There are few reports of in vivo muscle strength measurements in animal models of ICU‐acquired weakness (ICU‐AW). In this study we investigated whether the Escherichia coli (E. coli) septic peritonitis mouse model may serve as an ICU‐AW model using in vivo strength measurements and myosin/actin assays, and whether development of ICU‐AW is age‐dependent in this model. Methods: Young and old mice were injected intraperitoneally with E. coli and treated with ceftriaxone. Forelimb grip strength was measured at multiple time points, and the myosin/actin ratio in muscle was determined. Results: E. coli administration was not associated with grip strength decrease, neither in young nor in old mice. In old mice, the myosin/actin ratio was lower in E. coli mice at t = 48 h and higher at t = 72 h compared with controls. Conclusions: This E. coli septic peritonitis mouse model did not induce decreased grip strength. In its current form, it seems unsuitable as a model for ICU‐AW. Muscle Nerve 53 : 127–133, 2016     

Quantitative muscle ultrasound and quadriceps strength in patients with post‐polio syndrome

Introduction: We investigated whether muscle ultrasound can distinguish muscles affected by post‐polio syndrome (PPS) from healthy muscles and whether severity of ultrasound abnormalities is associated with muscle strength. Methods: Echo intensity, muscle thickness, and isometric strength of the quadriceps muscles were measured in 48 patients with PPS and 12 healthy controls. Results: Patients with PPS had significantly higher echo intensity and lower muscle thickness than healthy controls. In patients, both echo intensity and muscle thickness were associated independently with muscle strength. A combined measure of echo intensity and muscle thickness was more strongly related to muscle strength than either parameter alone. Conclusions: Quantitative ultrasound distinguishes healthy muscles from those affected by PPS, and measures of muscle quality and quantity are associated with muscle strength. Hence, ultrasound could be a useful tool for assessing disease severity and monitoring changes resulting from disease progression or clinical intervention in patients with PPS. Muscle Nerve 51 : 24–29, 2015