Mark Halaki

Development and psychometric testing of Korean language versions of 4 neck pain and disability questionnaires

Study Design. Cohort study. Objectives. To develop and establish the psychometric properties of Korean versions of 4 neck pain and disability questionnaires: the Neck Disability Index, Neck Pain and Disability Scale, Functional Rating Index, and Short Form McGill Pain Questionnaire (SFMPQ). Summary of Background Data. To our knowledge, there are no published Korean language neck pain and disability measures. Methods. Versions of each questionnaire in idiomatic modern Korean were developed with a process involving initial independent translation, synthesis of the translations, independent back translation, and review by an expert committee to achieve equivalence with the original English. Psychometric testing of the questionnaires with 261 subjects was undertaken to examine test-retest reliability, internal consistency, discriminative validity, and longitudinal construct validity. Results. Test-retest reliability of the translated versions of the 3 disability questionnaires was excellent (intraclass correlation coefficient[2,1] = 0.86–0.90). High internal consistency was found in the 3 disability questionnaires (Cronbach-α ranged from α = 0.88 for the Functional Rating Index to α = 0.96 for the Neck Pain and Disability Scale, and 0.82 for the SFMPQ). The visual analog scale subscale of the SFMPQ was the most responsive of the subscales (effect size = 1.44, standardized response mean = 1.37). The visual analog scale was also the most responsive pain and disability index in internal responsiveness analysis, although disability indexes showed marginally better responsiveness when compared with external standards. No floor or ceiling effects were observed. Conclusions. We conclude that the questionnaires were successfully translated and show acceptable measurement properties, and, as such, are suitable for use in clinical and research applications.

Shoulder Muscle Recruitment Patterns During Commonly Used Rotator Cuff Exercises: An Electromyographic Study

Background and Purpose: Graduated rotation exercises performed with the arm by the side are commonly used to improve rotator cuff (RC) muscle function. The aim of this study was to compare the pattern of recruitment of the RC muscles with that of other shoulder muscles that rotate the shoulder joint during these exercises. Subjects: The nondominant shoulders of 15 subjects who were healthy were tested. Methods: Activity in the infraspinatus, supraspinatus, subscapularis, latissimus dorsi, pectoralis major, and posterior deltoid muscles was recorded. Low-, medium-, and high-intensity rotation exercises were performed with a pulley system. Results: As the intensity of both internal and external rotation exercises increased, activity increased in a systematic manner in all muscles capable of producing rotation torque during concentric and eccentric contractions. Discussion and Conclusion: The results indicate that, in people who are healthy, the motor strategy used to deal with increasing rotation resistance with the arm in a pendant position is to gradually increase activity in all shoulder rotation torque-generating muscles.

Normalization of EMG Signals: To Normalize or Not to Normalize and What to Normalize to?

© 2012 Halaki and Ginn, licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Normalization of EMG Signals: To Normalize or Not to Normalize and What to Normalize to?

A comprehensive analysis of muscle recruitment patterns during shoulder flexion: An electromyographic study

Although flexion is a common component of the routine clinical assessment of the shoulder the muscle recruitment patterns during this movement are not clearly understood making valid interpretation of potential muscle dysfunction problematic. The purpose of this study was to comprehensively examine shoulder muscle activity during flexion in order to compare the activity levels and recruitment patterns of shoulder flexor, scapular lateral rotator and rotator cuff muscles. Electromyographic (EMG) data were recorded from 12 shoulder muscles sites in 15 volunteers. Flexion was performed in standing in the sagittal plane at no load, 20%, and 60% of each subjects maximum load. EMG data were normalized to maximum values obtained during maximum voluntary contractions. Results indicated that anterior deltoid, pectoralis major, supraspinatus, infraspinatus, serratus anterior, upper, and lower trapezius were activated at similar moderate levels. However, subscapularis was activated at low levels and significantly lower than supraspinatus and infraspinatus. Similar activity patterns across time were demonstrated in the muscles that produce flexion torque, laterally rotate the scapula, as well as supraspinatus and infraspinatus, and did not change as flexion load increased. The onset of activity in supraspinatus and anterior deltoid occurred at the same time and prior to movement of the limb at all loads with infraspinatus activity also occurring prior to movement onset at the medium and high load conditions only. Posterior rotator cuff muscles appear to be counterbalancing anterior translational forces produced during flexion and it would appear that supraspinatus is one of the muscles that consistently “initiates” flexion. Clin. Anat. 24:619–626, 2011.

The rotator cuff muscles have a direction specific recruitment pattern during shoulder flexion and extension exercises

A recent study has shown that posterior rotator cuff (RC) muscles are recruited at significantly higher levels than the anterior RC during shoulder flexion. It was proposed that the mechanism whereby the posterior RC muscles were providing shoulder stability during flexion was to counterbalance potential anterior humeral head translation caused by flexion torque producing muscles. This hypothesis implies that anterior RC activity should be higher than posterior RC activity during extension to prevent posterior humeral head translation. As the normal recruitment pattern of the RC during extension has not been established, the purpose of this study was to examine this hypothesis by comparing shoulder muscle activation levels and recruitment patterns during flexion and extension exercises. Electromyographic (EMG) activity was recorded from 9 shoulder muscles in 15 volunteers. Flexion and extension exercises were performed in prone at 20%, 50%, and 70% of each participants maximal load. A repeated measures ANOVA was used to determine differences between exercises, muscles and loads, while Pearsons correlation analysis was used to relate mean EMG patterns. During extension subscapularis and latissimus dorsi were activated at higher levels than during flexion; during flexion, supraspinatus, infraspinatus, deltoid, trapezius, and serratus anterior were more highly activated than during extension. In addition, the pattern of activity in each muscle did not vary with load. These results support the hypothesis that during flexion and extension the RC muscles are recruited in a direction specific manner to prevent potential antero-posterior humeral head translation caused by torque producing muscles.

Does passive mobilization of shoulder region joints provide additional benefit over advice and exercise alone for people who have shoulder pain and minimal movement restriction? A randomized controlled trial.

Background Passive mobilization of shoulder region joints, often in conjunction with other treatment modalities, is used for the treatment of people with shoulder pain and minimal movement restriction. However, there is only limited evidence supporting the efficacy of this treatment modality. Objective The purpose of this study was to determine whether passive mobilization of shoulder region joints adds treatment benefit over exercise and advice alone for people with shoulder pain and minimal movement restriction. Design This was a randomized controlled clinical trial with short-, medium- and longer-term follow-up. Setting The study was conducted in a metropolitan teaching hospital. Patients Ninety-eight patients with shoulder pain of local mechanical origin and minimal shoulder movement restriction were randomly allocated to either a control group (n=51) or an experimental group (n=47). Intervention Participants in both groups received advice and exercises designed to restore neuromuscular control at the shoulder. In addition, participants in the experimental group received passive mobilization specifically applied to shoulder region joints. Measurements Outcome measurements of shoulder pain and functional impairment, self-rated change in symptoms, and painful shoulder range of motion were obtained at 1, 3, and 6 months after entry into the trial. All data were analyzed using the intention-to-treat principle by repeated-measures analyses of covariance. Results No statistically significant differences were detected in any of the outcome measurements between the control and experimental groups at short-, medium-, or longer-term follow-up. Limitations Therapists and participants were not blinded to the treatment allocation. Conclusion This randomized controlled clinical trial does not provide evidence that the addition of passive mobilization, applied to shoulder region joints, to exercise and advice is more effective than exercise and advice alone in the treatment of people with shoulder pain and minimal movement restriction.

The use of surface electrodes to record infraspinatus activity is not valid at low infraspinatus activation levels.

Limited information is available to support the validity of using surface electrodes to record activity from infraspinatus. The aims of this study were to compare infraspinatus activity recorded using surface and intramuscular electrodes during several shoulder isometric and dynamic tasks and to establish if infraspinatus activity recorded using intramuscular electrodes is representative of whole muscle activity. Surface and intramuscular electrodes were placed over infraspinatus in nine subjects without shoulder pain. Isometric shoulder external rotation, at 0° and 90° abduction, and extension were performed at six loads. Dynamic shoulder flexion and abduction were performed at 70% maximum load. Results indicated that while surface and intramuscular electrodes record similar activation patterns when infraspinatus is moderately to highly activated (r and slope ∼ 1), only intramuscular electrodes accurately reflected low (<10%MVC) infraspinatus activity (r=0.95 ± 0.04, slope=15.6 ± 16.3). The linear relationship between the activity recorded with surface and intramuscular electrodes when infraspinatus is moderately to highly active also indicated that intramuscular recordings from infraspinatus are representative of activity in the whole muscle. To ensure validity in reporting infraspinatus activation patterns when studying functional shoulder tasks in which infraspinatus may be relatively active and inactive at different phases of these tasks, intramuscular electrodes should be used to record infraspinatus activity.

Human stick balancing: an intermittent control explanation

There are two issues in balancing a stick pivoting on a finger tip (or mechanically on a moving cart): maintaining the stick angle near to vertical and maintaining the horizontal position within the bounds of reach or cart track. The (linearised) dynamics of the angle are second order (although driven by pivot acceleration), and so, as in human standing, control of the angle is not, by itself very difficult. However, once the angle is under control, the position dynamics are, in general, fourth order. This makes control quite difficult for humans (and even an engineering control system requires careful design). Recently, three of the authors have experimentally demonstrated that humans control the stick angle in a special way: the closed-loop inverted pendulum behaves as a non-inverted pendulum with a virtual pivot somewhere between the stick centre and tip and with increased gravity. Moreover, they suggest that the virtual pivot lies at the radius of gyration (about the mass centre) above the mass centre. This paper gives a continuous-time control-theoretical interpretation of the virtual-pendulum approach. In particular, by using a novel cascade control structure, it is shown that the horizontal control of the virtual pivot becomes a second-order problem which is much easier to solve than the generic fourth-order problem. Hence, the use of the virtual pivot approach allows the control problem to be perceived by the subject as two separate second-order problems rather than a single fourth-order problem, and the control problem is therefore simplified. The theoretical predictions are verified using the data previously presented by three of the authors and analysed using a standard parameter estimation method. The experimental data indicate that although all subjects adopt the virtual pivot approach, the less expert subjects exhibit larger amplitude angular motion and poorly controlled translational motion. It is known that human control systems are delayed and intermittent, and therefore, the continuous-time strategy cannot be correct. However, the model of intermittent control used in this paper is based on the virtual pivot continuous-time control scheme, handles time delays and moreover masquerades as the underlying continuous-time controller. In addition, the event-driven properties of intermittent control can explain experimentally observed variability.

Phenotypic Variability of Childhood Charcot-Marie-Tooth Disease

IMPORTANCE Disease severity of childhood Charcot-Marie-Tooth disease (CMT) has not been extensively characterized, either within or between types of CMT to date. OBJECTIVE To assess the variability of disease severity in a large cohort of children and adolescents with CMT. DESIGN, SETTING, AND PARTICIPANTS A cross-sectional study was conducted among 520 children and adolescents aged 3 to 20 years at 8 universities and hospitals involved in the Inherited Neuropathies Consortium between August 6, 2009, and July 31, 2014, in Australia, Italy, the United Kingdom, and the United States. Data analysis was conducted from August 1, 2014, to December 1, 2015. MAIN OUTCOMES AND MEASURES Scores on the Charcot-Marie-Tooth Disease Pediatric Scale (CMTPedS), a well-validated unidimensional clinical outcome measure to assess disease severity. This instrument includes 11 items assessing fine and gross motor function, sensation, and balance to produce a total score ranging from 0 (unaffected) to 44 (severely affected). RESULTS Among the 520 participants (274 males) aged 3 to 20 years, CMT type 1A (CMT1A) was the most prevalent type (252 [48.5%]), followed by CMT2A (31 [6.0%]), CMT1B (15 [2.9%]), CMT4C (13 [2.5%]), and CMTX1 (10 [1.9%]). Disease severity ranged from 1 to 44 points on the CMTPedS (mean [SD], 21.5 [8.9]), with ankle dorsiflexion strength and functional hand dexterity test being most affected. Participants with CMT1B (mean [SD] CMTPedS score, 24.0 [7.4]), CMT2A (29.7 [7.1]), and CMT4C (29.8 [8.6]) were more severely affected than those with CMT1A (18.9 [7.7]) and CMTX1 (males: 15.3 [7.7]; females: 13.0 [3.6]) (P < .05). Scores on the CMTPedS tended to worsen principally during childhood (ages, 3-10 years) for participants with CMT4C and CMTX1 and predominantly during adolescence for those with CMT1B and CMT2A (ages, 11-20 years), while CMT1A worsened consistently throughout childhood and adolescence. For individual items, participants with CMT4C recorded more affected functional dexterity test scores than did those with all other types of CMT (P < .05). Participants with CMT1A and CMTX1 performed significantly better on the 9-hole peg test and balance test than did those with all other types of CMT (P < .05). Participants with CMT2A had the weakest grip strength (P < .05), while those with CMT2A and CMT4C exhibited the weakest ankle plantarflexion and dorsiflexion strength, as well as the lowest long jump and 6-minute walk test distances (P < .05). Multiple regression modeling identified increasing age (r = 0.356, β = 0.617, P < .001) height (r = 0.251, β = 0.309, P = .002), self-reported foot pain (r = 0.162, β = .114, P = .009), and self-reported hand weakness (r = 0.243, β = 0.203, P < .001) as independent predictors of disease severity. CONCLUSIONS AND RELEVANCE These results highlight the phenotypic variability within CMT genotypes and mutation-specific manifestations between types. This study has identified distinct functional limitations and self-reported impairments to target in future therapeutic trials.

The rotator cuff muscles are activated at low levels during shoulder adduction: an experimental study

QUESTION During isometric shoulder adduction in normal subjects, do the rotator cuff muscles activate more than other shoulder muscles? Are the activation patterns influenced by shoulder abduction angle or load? DESIGN A within-participant, repeated measures experimental study. PARTICIPANTS 15 healthy adults. INTERVENTION Participants performed an isometric adduction exercise at 30°, 60°, and 90° abduction in the scapular plane and at 25%, 50%, 75%, and 100% load. OUTCOME MEASURES During the exercises, a combination of indwelling and surface electromyographic recordings were taken from 11 shoulder muscles: supraspinatus, infraspinatus, subscapularis, pectoralis major, teres major, latissimus dorsi, rhomboid major, serratus anterior, lower trapezius, upper trapezius, and deltoid. RESULTS At 100% load, mean rotator cuff activation levels were low (supraspinatus at 3% of its maximum voluntary contraction, infraspinatus 27%, and subscapularis 27%) and significantly less than the activation levels of rhomboid major (81%), latissimus dorsi (103%), and teres major (76%) (F₁₀,₁₄₀ = 15.5, p < 0.01). No significant difference in activity levels of the rotator cuff muscles were recorded when isometric adduction was performed at 30°, 60°, or 90° abduction (p > 0.89). Among the muscles activated above minimum levels (> 10% of maximum voluntary contraction), mean activation levels increased as load increased (F₃,₄₂ = 72.0, p < 0.01) CONCLUSION Since isometric adduction in normal subjects does not produce moderate to high activation levels in any of the rotator cuff muscles tested, these results do not support the use of shoulder adduction to identify rotator cuff muscle dysfunction or strengthen the rotator cuff muscles.