Maximum Voluntary Isometric Contraction Testing Research Articles

P.399 - Effects of long-term eteplirsen treatment on upper limb function in patients with Duchenne muscular dystrophy: findings of two phase 2 clinical trials

Duchenne muscular dystrophy (DMD) is a progressive, degenerative neuromuscular disease caused by gene mutations that result in the absence or deficiency of dystrophin protein. Absence of dystrophin compromises the regenerative ability of muscle fibers, and, as muscle deterioration overtakes muscle growth, loss of upper limb function causes difficulties in performing daily activities and negatively impacts quality of life. Eteplirsen (Exondys 51; Sarepta Therapeutics, Cambridge, MA), the first FDA approved treatment for DMD in the US, is indicated for treatment of patients with DMD amenable to exon 51 skipping. Eteplirsen has not been approved for marketing outside of the United States. We evaluated long-term upper limb function outcomes in patients aged 7–13 years with DMD amenable to exon 51 skipping who participated in 2 eteplirsen clinical trials. Study 201, a 28-week trial, randomized patients to receive once-weekly intravenous eteplirsen infusions (30 mg/kg, n = 4; 50 mg/kg, n = 4) or placebo (n = 4) for 24 weeks. At week 25, all patients received open-label eteplirsen through week 28. In study 202, an open-label trial, all patients received once-weekly eteplirsen at the same dose as in study 201 through 240 weeks. Upper limb function tests included the 9-Hole Peg Test (seconds), a maximum voluntary isometric contraction test (MVICT) with a Quantitative Movement Assessment system to assess elbow flexion and extension and hand grip (kg). Study 201 enrolled 12 patients; all completed extension study 202. Following confirmation of dystrophin production, patients showed relative stability or minimal decline of upper limb function on all measures assessed through week 240. In conclusion, eteplirsen may slow the deterioration of upper arm function in patients with DMD amenable to exon 51 skipping.

Validity and reliability of elastic resistance bands for measuring shoulder muscle strength.

Valid and reliable measurements of muscle strength are important in sport medicine. This study assesses concurrent validity and intrarater reliability (test-retest reliability) of elastic resistance bands for measuring shoulder muscle strength. Altogether, 50 healthy adults [mean age 36.0 (SD: 11.6), 29 women and 21 men] participated in testing and retesting 1-2weeks later. The maximal elastic resistance (TheraBand) that each participant could hold for 3s during standing bilateral shoulder abduction to 90° was converted into torque and validated against gold standard maximal voluntary isometric contraction (MVC) (Vishay force transducer) performed unilaterally while lying supine. The intrarater reliability of both tests were high; for the MVC and elastic band test, respectively, ICC(3,1) was 0.98 (95% CI: 0.97-0.99) and 0.99 (95% CI: 0.98-1.00), and measurement error was 4.8% (95% CI: 3.7-5.9) and 4.7% (95% CI: 3.1-6.2). For concurrent validity, ICC(3,1) was 0.96 (95% CI: 0.95-0.98) and measurement error was 8.1% (95% CI: 6.6-9.6), and the elastic band test explained 93% of the variance in the MVC test. However, the elastic band test produced systematically lower torque values than the MVC [56.5 (SD: 26.8) vs 66.5 (SD: 25.5) Nm, P<0.01]. In conclusion, the test for shoulder muscle strength using elastic resistance bands has excellent validity and reliability, but produces systematically lower torque values than MVC. The reason for the lower torque values may be that the elastic band test has an initial concentric phase and is performed bilaterally and standing upright.

Muscle adaptation to 21 Straight Days of Elbow Flexor Exercise in Trained Individuals

It is recommended for individuals engaging in resistance training to allow at least 48 h of recovery before repeating exercise which stresses the same muscle group. Despite this, studies have shown that training frequencies as high as four, five, or even six days per week have yielded robust increases in muscle size and strength; however, protocols implementing greater frequencies remain untested. PURPOSE: To determine the muscle size and strength adaptations following 21 straight days of elbow flexion exercise in well trained individuals. METHODS: Using a within subject design, five trained individuals were assigned both a control and experimental arm in a randomized fashion. The control arm performed a one repetition maximum (1RM) and maximal voluntary isometric contraction (MVC) every day for 21 straight days, while the experimental arm performed the same 1RM and MVC test in addition to three sets of elbow flexion exercises at 70% 1RM. Pre to post muscle thickness and strength differences within each condition and median differences between conditions were determined using non-parametric Wilcoxin tests. All significance was set at p≤ .05. Data are presented as median (25th, 75th percentile). RESULTS: 1RM strength increased from Pre to Post in both the experimental [Pre: 25.2 (22.6, 33.1), Post: 27.7 (25.1, 34.9) kg] and control [Pre: 22.5 (21.8, 32.6), Post: 25.0 (23.7, 34.2) kg] (p=0.043) arm, with no difference between arms (p=0.345). Individual data plots indicated that muscle growth occurred in the experimental arm for all individuals, however no changes in muscle size were observed at any location in the control arm. Median muscle size differences within the experimental condition were as follows: 50% (Pre: 3.8, Post: 4.2 cm; p=0.066), 60% (Pre: 4.4, Post: 4.7 cm; p=0.034) and 70% (Pre: 4.9, Post: 5.0 cm; p=0.066). Median differences in muscle size between the experimental and control arms found significant differences at the 50% site (p=0.041) with a trend at the 60% (p=0.068) and 70% (p=0.059) sites. CONCLUSIONS: Everyday training of the same muscle group appears to be effective for increasing muscle size over a relatively short duration, in trained individuals. Additionally, performing only 1RM testing every day may increase 1RM strength, which does not appear to be augmented by greater exercise volume.

Optimal Combinations of Isometric Normalization Tests for the Production of Maximum Voluntary Activation of the Shoulder Muscles

ObjectiveTo identify the smallest combinations of maximum voluntary isometric contraction (MVIC) tests that produce near-maximum voluntary activation (MVA) for a large proportion of participants for the shoulder girdle muscles. DesignCross-sectional study. SettingResearch center. ParticipantsHealthy participants (N=38). InterventionsNot applicable. Main Outcome MeasuresThe electromyography of 12 shoulder muscles was recorded while participants performed 15 MVIC tests. The smallest combinations of MVIC tests that met our acceptance criterion (ie, produce 90% of MVA for 90% of participants) were identified. Optimal combinations were identified for each of the 12 muscles individually and for the 12 muscles simultaneously. Electromyographic activation levels of the 95th highest percentile obtained with our optimal combinations and with the Four Normalization Tests previously recommended were compared using paired t tests. ResultsBetween 2 and 6 MVIC tests were required for each of the 12 muscles, and 12 MVIC tests were required for the 12 muscles to meet the acceptance criterion. These optimal combinations produced electromyographic activation levels of the 95th highest percentile comprised between 97% and 100% of MVA. These electromyographic activation levels were significantly higher than the electromyographic activation levels obtained with the Four Normalization Tests. ConclusionsAlthough the number of MVIC tests to normalize 12 shoulder muscles was increased compared with previous recommendations, the proposed method ensures that near-MVA (>90%) was obtained for a large proportion of participants (>90%). Moreover, because electromyographic activation levels of the 95th highest percentile were at least 97% of MVA, the identified combinations could reduce the interparticipant variability. The proposed combinations could help to improve electromyographic normalization and therefore reduce the misinterpretations regarding shoulder muscle activation levels.

Differences in leg muscle activity and body sway between elderly adults able and unable to maintain one-leg stance for 1min: the effect of hand support.

One-leg stance (OLS) training is often used to prevent falls in the elderly. The burden imposed on the supporting lower limb during OLS may differ depending on whether hand support is used, particularly in patients with decreased lower-limb strength. Here we examined the effect of hand support on leg muscle activity and body sway during OLS in elderly subjects able to maintain OLS for 1min unaided [able group (AG), n=13] and those who were unable to do so [unable group (UG), n=11]. All subjects performed OLS unaided and OLS with front support (OLS-FS) using one hand for 1min each. We estimated leg muscle activity [mean and maximum % root mean square (%RMS)] and body sway (total, X-axis, and Y-axis path lengths) for both tests. %RMS was calculated according to the results of the maximum voluntary isometric contraction test. The overall average mean and maximum %RMS for the tibialis anterior muscle was larger in UG than in AG. In AG, tibialis anterior muscle mean and maximum %RMS and body sway was larger during OLS than during OLS-FS. Total and X-axis path lengths were larger during the first 20s OLS phase in AG and the first 20s OLS-FS phase in UG. These results highlight the need to differentiate between patients able and unable to perform OLS unaided for training because of differences in leg muscle activity.

Optimal Normalization Tests for Muscle Activation of the Levator Scapulae, Pectoralis Minor, and Rhomboid Major: An Electromyography Study Using Maximum Voluntary Isometric Contractions

ObjectiveTo identify maximum voluntary isometric contraction (MVIC) test positions for the deeper-lying scapulothoracic muscles (ie, levator scapulae, pectoralis minor, rhomboid major), and to provide a standard set of a limited number of test positions that generate an MVIC in all scapulothoracic muscles. DesignCross-sectional study. SettingPhysical and rehabilitation medicine department. ParticipantsHealthy subjects (N=21). InterventionsNot applicable. Main Outcome MeasuresMean peak electromyographic activity from levator scapulae, pectoralis minor, and rhomboid major (investigated with fine-wire electromyography) and from upper trapezius, middle trapezius, lower trapezius, and serratus anterior (investigated with surface electromyography) during the performance of 12 different MVICs. ResultsThe results indicated that various test positions generated similar high mean electromyographic activity and that no single test generated maximum activity for a specific muscle in all subjects. The results of this study support using a series of test positions for normalization procedures rather than a single exercise to increase the likelihood of recruiting the highest activity in the scapulothoracic muscles. ConclusionsA standard set of 5 test positions was identified as being sufficient for generating an MVIC of all scapulothoracic muscles: seated T, seated U 135°, prone T–thumbs up, prone V–thumbs up, and supine V–thumbs up. A standard set of test positions for normalization of scapulothoracic electromyographic data that also incorporates the levator scapulae, pectoralis minor, and rhomboid major muscles is 1 step toward a more comprehensive understanding of normal and abnormal muscle function of these muscles and will help to standardize the presentation of scapulothoracic electromyographic muscle activity.

Reachable workspace reflects dynamometer-measured upper extremity strength in facioscapulohumeral muscular dystrophy.

It is not known whether a reduction in reachable workspace closely reflects loss of upper extremity strength in facioscapulohumeral muscular dystrophy (FSHD). In this study we aimed to determine the relationship between reachable workspace and quantitative upper extremity strength measures. Maximal voluntary isometric contraction (MVIC) testing of bilateral elbow flexion and shoulder abduction by hand-held dynamometry was performed on 26 FSHD and 27 control subjects. In addition, Kinect sensor-based 3D reachable workspace relative surface areas (RSAs) were obtained. Loading (500-g weight) effects on reachable workspace were also evaluated. Quantitative upper extremity strength (MVIC of elbow flexion and shoulder abduction) correlated with Kinect-acquired reachable workspace RSA (R = 0.477 for FSHD, P = 0.0003; R = 0.675 for the combined study cohort, P < 0.0001). Progressive reduction in RSA reflected worsening MVIC measures. Loading impacted the moderately weak individuals the most with additional reductions in RSA. Reachable workspace outcome measure is reflective of upper extremity strength impairment in FSHD.

Correlação e reprodutibilidade de testes abdominais em mulheres jovens

The purpose of this study was to investigate possible correlations between the values of 1 minute abdominal tests, 2 minutes with bench, a repetition maximum, a repe- tition maximum with 70% of 1RM and maximum voluntary isometric contraction test and then, to verify the reproducibility of them in young women. The study was composed by 15 trained women (26.22 ± 4.67 ages). The tests were randomly performed in different days with minimum of 48 hours of interval between collections. After of 7-10 days interval, the tests were performed again. The present results suggested it is possible to conclude that abdominal tests present a good capacity of reproducibility. Besides this, the 1min and 2min tests have presented a good relation with the maximum strength test (1RM), however the maximum voluntary isometric contraction and repetition maximum with 70% of 1RM tests did not presented any correlation with the other tests.

P.14.17 Evaluation of the ability of timed walking tests to quantify function in sporadic inclusion body myositis

Sporadic inclusion body myositis (sIBM) causes progressive loss of ambulatory function due to declining muscle strength. Although the cause is currently unknown, clinical trials are underway with the goal of improving strength and function in individuals affected with this disease. Selection of appropriate outcome measures is critical for the success of these trials. The 6-min walk test (6MWT) has been the de facto standard for assessing function in neuromuscular disease, however, this test has not been well studied in subjects with sIBM. 55 individuals with sIBM (43 male, 12 female; age range: 46–85 years; mean age: 66.8 ± 8.4 years) completed a battery of strength and functional testing to determine the optimal walking assessment to demonstrate change throughout clinical trials for subjects with this diagnosis. Strength was measured using maximum voluntary isometric contraction testing of the hips, knees, and ankles using a fixed quantitative muscle analysis system. Functional testing included the 2-min walk test (2MWT), 6MWT, modified Timed Up and Go (mTUG), time to ascend and descend 4 stairs, and stepping up on curbs (SoC). Our results indicate that both the 2MWT and 6MWT are highly correlated (r = 0.975). Both tests are also similarly correlated with the other functional measures and lower extremity strength. Further research is needed to determine longitudinal changes on the 2MWT in individuals with sIBM, however preliminary evidence suggests that the 2MWT is a possible alternative to walking tests of longer duration. Sporadic inclusion body myositis (sIBM) causes progressive loss of ambulatory function due to declining muscle strength. Although the cause is currently unknown, clinical trials are underway with the goal of improving strength and function in individuals affected with this disease. Selection of appropriate outcome measures is critical for the success of these trials. The 6-min walk test (6MWT) has been the de facto standard for assessing function in neuromuscular disease, however, this test has not been well studied in subjects with sIBM. 55 individuals with sIBM (43 male, 12 female; age range: 46–85 years; mean age: 66.8 ± 8.4 years) completed a battery of strength and functional testing to determine the optimal walking assessment to demonstrate change throughout clinical trials for subjects with this diagnosis. Strength was measured using maximum voluntary isometric contraction testing of the hips, knees, and ankles using a fixed quantitative muscle analysis system. Functional testing included the 2-min walk test (2MWT), 6MWT, modified Timed Up and Go (mTUG), time to ascend and descend 4 stairs, and stepping up on curbs (SoC). Our results indicate that both the 2MWT and 6MWT are highly correlated (r = 0.975). Both tests are also similarly correlated with the other functional measures and lower extremity strength. Further research is needed to determine longitudinal changes on the 2MWT in individuals with sIBM, however preliminary evidence suggests that the 2MWT is a possible alternative to walking tests of longer duration.

Upper and Lower Limb Muscles in Patients With COPD: Similarities in Muscle Efficiency But Differences in Fatigue Resistance

Peripheral muscle dysfunction is a common finding in patients with COPD; however, the structural adaptation and functional impairment of the upper and lower limb muscles do not seem to be homogenous. We compared muscle fatigue and recovery time between 2 representative muscles: the middle deltoid and the quadriceps femoris. Twenty-one subjects with COPD (FEV1 46.1 ± 10.3% of predicted) underwent maximal voluntary isometric contraction and an endurance test (60% of maximal voluntary isometric contraction, to the limit of tolerance). The maximal voluntary isometric contraction test was repeated after 10 min, 30 min, 60 min, and 24 hours for both the quadriceps femoris and middle deltoid. Surface electromyography was recorded throughout the endurance test. Maximal voluntary isometric contraction significantly decreased only for the middle deltoid between 10 and 60 min after the endurance test. A significant increase of the root mean square and a greater decline in median frequency throughout the endurance test occurred for the middle deltoid, compared with the quadriceps femoris. When dyspnea and fatigue scores were corrected by endurance time, higher values were observed for the middle deltoid (0.07 and 0.08, respectively) in relation to the quadriceps femoris (0.02 and 0.03, respectively). Subjects with COPD had a higher fatigability of a representative upper limb muscle (middle deltoid) than a lower limb muscle (quadriceps femoris).

SMA valiant trial: A prospective, double‐blind, placebo‐controlled trial of valproic acid in ambulatory adults with spinal muscular atrophy

An open-label trial suggested that valproic acid (VPA) improved strength in adults with spinal muscular atrophy (SMA). We report a 12-month, double-blind, cross-over study of VPA in ambulatory SMA adults. There were 33 subjects, aged 20–55 years, included in this investigation. After baseline assessment, subjects were randomized to receive VPA (10–20 mg/kg/day) or placebo. At 6 months, patients were switched to the other group. Assessments were performed at 3, 6, and 12 months. The primary outcome was the 6-month change in maximum voluntary isometric contraction testing with pulmonary, electrophysiological, and functional secondary outcomes. Thirty subjects completed the study. VPA was well tolerated, and compliance was good. There was no change in primary or secondary outcomes at 6 or 12 months. VPA did not improve strength or function in SMA adults. The outcomes used are feasible and reliable and can be employed in future trials in SMA adults.

Reevaluating measures of disease progression in facioscapulohumeral muscular dystrophy

Recent advances in the understanding of the molecular pathophysiology of facioscapulohumeral muscular dystrophy (FSHD) have identified potential therapeutic targets. Consequently, an accurate understanding of disease progression in FSHD is crucial for the design of future clinical trials. Data from 228 subjects in 3 clinical trials and 1 natural history study were compared to examine disease progression in FSHD. All studies utilized the same techniques for manual muscle testing and maximum voluntary isometric contraction testing. Both techniques yield a total strength score that can be followed over time as an indicator of disease progression. Whereas natural history data showed a decrease in strength over 1 year, there was an apparent increase in strength at 6 months in 2 of the 3 clinical trials in both the placebo and treatment groups, that persisted for up to 1 year for maximum voluntary isometric contraction testing. Variability estimates from the clinical trial data were consistent with those seen in the natural history data. Patients in clinical trials in FSHD may have better outcomes than those in natural history studies, regardless of treatment assignment, emphasizing the importance of placebo groups and the need for caution when interpreting the strength results of controlled and uncontrolled trials.

Rate of Force Development as an Adjunctive Outcome Measure for Return-to-Sport Decisions After Anterior Cruciate Ligament Reconstruction

Descriptive, prospective, longitudinal single-cohort study. To investigate the rate of force development to 30% (RFD(30)), 50% (RFD(50)), and 90% (RFD(90)) of maximal voluntary isometric contraction (MVIC) as an adjunct outcome measure for determining readiness for return to sport following an anterior cruciate ligament (ACL) reconstruction. One criterion of full recovery following an ACL reconstruction is the ability to achieve 85% or 90% of the maximal strength of the contralateral limb. However, the time required to develop muscular strength in many types of daily and sports activities is considerably shorter than that required to achieve maximal strength. Therefore, in addition to maximal strength, neuromuscular functions such as RFD should also be considered in the definition of recovery. Forty-five male professional soccer players who underwent an ACL reconstruction were recruited. Assessment with the International Knee Documentation Committee (IKDC) Subjective Knee Evaluation Form, Tegner score, and KT1000 instrumented arthrometer was performed postinjury/prereconstruction and at 6 and 12 months after ACL reconstruction. MVIC, RFD(30), RFD(50), and RFD(90) testing was performed preinjury, as part of standard preseason assessment, and at 6 and 12 months post-ACL reconstruction. The average MVIC value 6 months postreconstruction was 97% of the preinjury average value. In contrast, at 6 months, the RFD(30), RFD(50), and RFD(90) values were 80% (P = .04), 77% (P = .03), and 63% (P = .007), respectively, of the preinjury values. The mean RFD values for the reconstructed knee attained or exceeded 90% of the preinjury mean values only at the 12-month post-ACL reconstruction assessment (RFD(30), P = .86; RFD(50), P = .51; RFD(90), P = .56). Despite the near recovery of MVIC strength to preinjury levels, there were still significant deficits in RFD at 6 months post-ACL reconstruction. An RFD similar to the preinjury RFD was achieved at 12 months post-ACL reconstruction, following a rehabilitation program focusing on muscle power. These results suggest that, following an ACL reconstruction, RFD criteria may be a useful adjunct outcome measure for the decision to return athletes to sports. J Orthop Sports Phys Ther 2012;42(9):772-780, Epub 19 July 2012. doi:10.2519/jospt.2012.3780.

A Prospective, Randomized Controlled Trial of Valproic Acid in Ambulant Adults with SMA: The VALIANT Trial (S25.002)

Objective: To report the results of a randomized, double-blind, placebo-controlled trial of valproic acid (VPA) in ambulatory adults with spinal muscular atrophy (SMA). Background Much evidence suggests that VPA, a histone deacetylase inhibitor, might benefit patients with SMA by modulating SMN2 splicing to increase production of full-length SMN transcript from SMN2 . Five open-label human trials of VPA in SMA showed a benefit in strength and function. Design/Methods: This was a prospective, randomized, double blind, 12 month study in SMA adults over 18 years old. After two baseline assessments, subjects were randomized to VPA or placebo and then crossed over to the other group at six months. Patients were evaluated at 3, 6, and 12 months. Primary outcome was the six-month strength change by maximum voluntary isometric contraction testing. Secondary outcomes included adverse events and changes in ulnar compound motor action potential amplitude and motor unit number estimation, strength by handheld dynamometry, 6 minute walk test, pulmonary function, functional rating scale (SMAFRS), and quality of life assessment. Results: Thirty-three subjects (20 M, 13 F; mean age 37.1) were enrolled; 16 patients were initially on VPA and 17 on placebo. Three patients did not complete the study; two due to adverse events not related to VPA and one withdrew. There were no significant adverse events. There was no significant change in the primary or secondary outcome after six months of treatment. Conclusions: VPA at doses used in this study did not improve strength or function in ambulatory SMA adults, and is compatible with earlier published negative CARNI-VAL studies in SMA children. The Project Cure-SMA group is currently analyzing data from open label studies in infants with Type 1 that should provide additional important information on VPA and its effect on biomarkers. Supported by: This study was entirely funded by FSMA through the Project Cure Investigators Network, and NIH CCTS funding at Ohio State. Disclosure: Dr. Elsheikh has nothing to disclose. Dr. Kolb has nothing to disclose. Dr. King has nothing to disclose. Dr. Chelnick has nothing to disclose. Dr. Scott has nothing to disclose. Dr. LaSalle has nothing to disclose. Dr. Krosschell has nothing to disclose. Dr. Reyna has nothing to disclose. Dr. Swoboda has received research support from BioMarin Pharmaceuticals and Orphamed, Dr. Kissel has nothing to disclose.

Knee extensor strength exhibits potential to predict function in sporadic inclusion‐body myositis

In this study we address the challenging issue of potential use of muscle strength to predict function in clinical trials. This has immediate relevance to translational studies that attempt to improve quadriceps strength in sporadic inclusion-body myositis (sIBM). Maximum voluntary isometric contraction testing as a measure of muscle strength and a battery of functional outcomes were tested in 85 ambulatory subjects with sIBM. Marked quadriceps weakness was noted in all patients. Strength was correlated with distance walked at 2 and 6 minutes. Additional correlations were found with time to get up from a chair, climb stairs, and step up on curbs. Quadriceps (knee extensor) strength correlated with performance in this large cohort of sIBM subjects, which demonstrated its potential to predict function in this disease. These data provide initial support for use of muscle strength as a surrogate for function, although validation in a clinical trial is required.

Strength Training's Chronic Effects on Muscle Architecture Parameters of Different Arm Sites

Strength training generates alterations in muscle geometry, which can be monitored by imaging techniques as, for example, the ultrasound (US) technique. There is no consensus about the homogeneity of hypertrophy in different muscle sites. Therefore, the purpose of this study was to compare the muscle thickness (MT) and pennation angle (PA) in 3 different sites (50, 60, and 70% of arm length) of the biceps brachii and triceps brachii after 12 weeks of strength training. Forty-nine healthy untrained men were divided into 2 groups: Training Group ([TG, n = 40] 29.90 ± 1.72 years; 79.53 ± 11.84 kg; 173 ± 0.6 cm) and Control Group (n = 9 25.89 ± 3.59 years; 73.96 ± 9.86 kg; 171 ± 6 cm). The TG underwent a strength training program during 12 weeks, which included exercises such as a free-weight bench press, machine lat pull-down, triceps extension in lat pull-down, and standing free-weight biceps curl with a straight bar. A US apparatus was used to measure the PA and MT at the 3 sites. The maximal voluntary isometric contraction (MVC) test was conducted for each muscle group. After 12 weeks of training, a significant difference was observed between MT in biceps brachii, with an improvement of 12% in the proximal site, whereas the distal site increased by only 4.7% (p < 0.05). For the long head of the triceps brachii, the MT and PA at the 3 sites presented significant increases, but no significant variation was observed among them, probably because of the pennated-fiber arrangement. The MVC increased significantly for both muscle groups. The results indicated that the strength training program was efficient in promoting hypertrophy in both muscles, but with dissimilar responses of the pennated and fusiform muscle architecture at different arm sites.

Muscle Activation and Perceived Loading During Rehabilitation Exercises: Comparison of Dumbbells and Elastic Resistance

High-intensity resistance training plays an essential role in the prevention and rehabilitation of musculoskeletal injuries and disorders. Although resistance exercises with heavy weights yield high levels of muscle activation, the efficacy of more user-friendly forms of exercise needs to be examined. The aim of this study was to investigate muscle activation and perceived loading during upper-extremity resistance exercises with dumbbells compared with elastic tubing. A single-group, repeated-measures study design was used. Exercise evaluation was conducted in a laboratory setting. Sixteen female workers (aged 26-55 years) without serious musculoskeletal diseases and with a mean neck and shoulder pain intensity of 7.8 on a 100-mm visual analog scale participated in the study. Electromyographic (EMG) activity was measured in 5 selected muscles during the exercises of lateral raise, wrist extension, and shoulder external rotation during graded loadings with dumbbells (2-7.5 kg) and elastic tubing (Thera-Band, red to silver resistance). The order of exercises and loadings was randomized for each individual. Electromyographic amplitude was normalized to the absolute maximum EMG amplitude obtained during maximal voluntary isometric contraction and exercise testing. Immediately after each set of exercise, the Borg CR10 scale was used to rate perceived loading during the exercise. Resistance exercise with dumbbells as well as elastic tubing showed increasing EMG amplitude and perceived loading with increasing resistance. At the individually maximal level of resistance for each exercise-defined as the 3 repetitions maximum-normalized EMG activity of the prime muscles was not significantly different between dumbbells (59%-87%) and elastic tubing (64%-86%). Perceived loading was moderately to very strongly related to normalized EMG activity (r=.59-.92). Limitations The results of this study apply only for exercises performed in a controlled manner (ie, without sudden jerks or high acceleration). Comparably high levels of muscle activation were obtained during resistance exercises with dumbbells and elastic tubing, indicating that therapists can choose either type in clinical practice. The Borg CR10 can be a useful aid in estimating intensity of individual rehabilitation protocols.

Electrical impedance myography to assess outcome in amyotrophic lateral sclerosis clinical trials

Objective Standard outcome measures used for amyotrophic lateral sclerosis (ALS) clinical trials, including the ALS functional rating scale-revised (ALSFRS-R), maximal voluntary isometric contraction testing (MVICT), and manual muscle testing (MMT), are limited in their ability to detect subtle disease progression. Electrical impedance myography (EIM) is a new non-invasive technique that provides quantitative data on muscle health by measuring localized tissue impedance. This study investigates whether EIM could provide a new outcome measure for use in ALS clinical trials work. Methods Fifteen ALS patients underwent repeated EIM measurements of one or more muscles over a period of up to 18 months and the primary outcome variable, θ z-max , measured. The θ z-max megascore was then calculated using the same approach as has been applied in the past for MVICT. This and the MMT data were then used to assess each measure’s statistical power to detect a given effect on disease progression in a hypothetical planned clinical therapeutic trial. Results θ z-max showed a mean decline of about 21% for the test period, averaged across all patients and all tested muscles. The θ z-max megascore had a power of 73% to detect a 10% treatment effect in our planned hypothetical trial, as compared to a 28% power for MMT. These results also compared favorably to historical data for ALSFRS-R and MVICT arm megascore from the trial of celecoxib in ALS, where both measures had only a 23% power to detect the same 10% treatment effect. Conclusions The θ z-max megascore may provide a powerful new outcome measure for ALS clinical trials. Significance The application of EIM to future ALS trials may allow for smaller, faster studies with an improved ability to detect subtle progression of the disease and treatment effects.

Maximum voluntary isometric contraction: Reference values and clinical application

Maximum voluntary isometric contraction (MVIC) is a standardized method for measurement of muscle strength in patients with neuromuscular disease. Values obtained from MVIC testing are difficult to interpret at present as normative data are limited. The objective of this study was to generate reference values for MVIC. A convenience sample of 494 healthy men and women aged 20-76 years was recruited. MVIC testing was performed on nine muscle groups bilaterally: neck flexors, shoulder abductors, shoulder adductors, elbow and knee flexors and extensors, and hip and ankle flexors. MVIC was performed using the Quantitative Muscle Assessment system. Age and sex related reference values were calculated for each muscle group using quantile regression. A clinical reporting system was developed to facilitate interpretation of patient values with reference to normal percentiles. Reference values generated from this study can be used to determine the presence and extent of muscle weakness in a given population and to evaluate the effectiveness of treatment interventions.

An alternative test of electromyographic normalization in patients

The value of electromyography (EMG) in the interpretation of normal and pathological movement depends on recording, processing, and normalization procedures. Traditionally, maximum voluntary isometric contraction (MVIC) of individual muscles is commonly used for EMG normalization. However, this is a time- and energy-consuming procedure, especially in patients. The aim of the present study was to compare an alternative method of recording the MVIC of lower-limb muscles to the traditional method in healthy, young subjects as well as individuals with a stroke. The alternative method consisted of recording the maximum effort of several thigh and leg muscles simultaneously using two tasks on a dynamometer. Five healthy subjects and five individuals who had a stroke performed both MVIC tasks. The healthy group repeated the test 3 h later on the same day. In general, the method of computing maximum EMG from the alternative MVIC test yielded values that were equal or greater than those from the traditional test in both groups. In the healthy group, muscles showed similar EMGs in the two sessions, indicating that the test was reliable. These results suggest that the less time-consuming alternative method of computing maximum EMG values used here provides a reasonable alternative when time and fatigue become issues, especially when testing patient populations.