Cross-education of muscular strength following unilateral resistance training: a meta-analysis.

PURPOSE: Cross-education (CE) of strength is a well-known phenomenon whereby exercise of one limb can induce strength gains in the contralateral untrained limb. The only available meta-analyses on CE, which date back to a decade ago, estimated a modest 7.8% increase in contralateral strength following unilateral training. However, in recent years new evidences have outlined larger contralateral gains, which deserve to be systematically evaluated. Therefore, the aim of this meta-analysis was to appraise current data on CE and determine its overall magnitude of effect. METHODS: Five databases were searched from inception to December 2016. All randomized controlled trials focusing on unilateral resistance training were carefully checked by two reviewers who also assessed the eligibility of the identified trials and extracted data independently. The risk of bias was assessed using the Cochrane Risk-of-Bias tool. RESULTS: Thirty-one studies entered the meta-analysis. Data from 785 subjects were pooled and subgroup analyses by body region (upper/lower limb) and type of training (isometric/concentric/eccentric/isotonic-dynamic) were performed. The pooled estimate of CE was a significant 11.9% contralateral increase (95% CI 9.1-14.8; p < 0.00001; upper limb: + 9.4%, p < 0.00001; lower limb: + 16.4%, p < 0.00001). Significant CE effects were induced by isometric (8.2%; p = 0.0003), concentric (11.3%; p < 0.00001), eccentric (17.7%; p = 0.003) and isotonic-dynamic training (15.9%; p < 0.00001), although a high risk of bias was detected across the studies. CONCLUSIONS: Unilateral resistance training induces significant contraction type-dependent gains in the contralateral untrained limb. Methodological issues in the included studies are outlined to provide guidance for a reliable quantification of CE in future studies.

Time course of strength adaptations following high-intensity resistance training in individuals with multiple sclerosis.

PURPOSE: No evidence exists regarding the time course and clinical relevance of muscle strength improvements following resistance training in people with multiple sclerosis (PwMS). The purpose of this study was to investigate the temporal course and the clinical meaningfulness of the changes in strength induced by high-intensity resistance training and whether these changes impact on muscle endurance to fatigue and functional outcomes. METHODS: PwMS with predominantly unilateral hyposthenia of the ankle dorsiflexors underwent a 6-week isokinetic training of the more affected ankle dorsiflexion muscles. Maximal strength was measured at baseline, during the training on a weekly basis, at the end of the intervention (POST) and at the 12-week follow-up. Muscle endurance to fatigue, mobility and walking outcomes were assessed at baseline, POST and follow-up. Reproducibility and responsiveness analyses were performed. RESULTS: Significant gains in muscle strength were already detected after 3 weeks of training with no further improvements in the following weeks. These improvements exceeded the cutoff values for relevant changes and were also positively correlated to improved muscle endurance to fatigue and mobility measures. None of the observed changes in muscle performance and functional outcomes was retained at the follow-up. CONCLUSIONS: Preliminary evidence showed that 3 weeks of high-intensity resistance training induces consistent and meaningful improvements in muscle performance of the ankle dorsiflexors in PwMS. These findings may have practical dose-response and cost-effectiveness implications in the management of MS-induced muscle weakness, potentially enhancing the understanding of the response to training exhibited by PwMS. TRIAL REGISTRATION NUMBER: ClinicalTrials.gov identifier NCT02010398; December 2013.

No evidence of neural adaptations following chronic unilateral isometric training of the intrinsic muscles of the hand: a randomized controlled study.

PURPOSE: To test whether long-term cortical adaptations occur bilaterally following chronic unilateral training with a simple motor task. METHODS: Participants (n = 34) were randomly allocated to a training or control groups. Only the former completed a 4-week maximal-intensity isometric training of the right first dorsal interosseus muscle through key pinching. Maximal strength was assessed bilaterally in four different movements progressively less similar to the training task: key, tip and tripod pinches, and handgrip. Transcranial magnetic stimulation was used to probe, in the left and right primary hand motor cortices, a number of standard tests of cortical excitability, including thresholds, intra-cortical inhibition and facilitation, transcallosal inhibition, and sensory-motor integration. RESULTS: Training increased strength in the trained hand, but only for the tasks specifically involving the trained muscle (key +8.5 %; p < 0.0005; tip +7.2 %; p = 0.02). However, the effect size was small and below the cutoff for meaningful change. Handgrip and tripod pinch were instead unaffected. There was a similar improvement in strength in the untrained hand, i.e., a cross-education effect (key +6.4 %; p = 0.02; tip +4.7 %; p = 0.007). Despite these changes in strength, no significant variation was observed in any of the neurophysiological parameters describing cortico-spinal and intra-cortical excitability, inter-hemispheric inhibition, and cortical sensory-motor integration. CONCLUSIONS: A 4-week maximal-intensity unilateral training induced bilaterally spatial- and task-specific strength gains, which were not associated to direct or crossed cortical adaptations. The observed long-term stability of neurophysiological parameters might result from homeostatic plasticity phenomena, aimed at restoring the physiological inter-hemispheric balance of neural activity levels perturbed by the exercise. TRIAL REGISTRATION NUMBER: ClinicalTrials.gov identifier NCT02010398.

Characterization of ankle dorsiflexors performance in healthy subjects following maximal-intensity isokinetic resistance training.

The purpose of this randomized trial was to examine, in healthy subjects, the effect of unilateral isokinetic-concentric training of the dominant ankle dorsiflexors (DF) on the peak moment (PM), mean PM (MPM), maximal work and mean work (meanW). Thirty volunteers (26.7±4.6years old) underwent bilateral isokinetic testing of ankle DF at 45 and 90°/s. Participants were randomly assigned to a control or a training group. The training lasted 4weeks (4-day/week). All dynamometric parameters increased significantly only in the training group for the trained leg (p<0.05), with greater gains in work (32-47% at 45°/s and 31-41% at 90°/s) than moment variables (14-18% at 45°/s and 14-28% at 90°/s). Similar increases in strength were also noted at both angular velocities in the untrained leg (p<0.01) for both work and moment parameters, depicting a cross-training effect. Correlations between 'moments' and 'works' increased in both legs after training from 0.59-0.77 to 0.79-0.95. Principal component analysis indicated that, at baseline, PM showed the highest weight on DF performance; after training, meanW at 90°/s and MPM at 45°/s exhibited the highest loadings. High-intensity training of ankle DF increase the ability in generating energy throughout the entire range of motion rather than maximizing the PM.

Effects of abdominal surgery through a midline incision on postoperative trunk flexion strength in patients with colorectal cancer.

BACKGROUND: Abdominal surgery with bowel resection through a midline or transverse incision is performed in most cases of colorectal cancer (CRC). Both incisions affect abdominal wall function and may lead to differences in postoperative clinical outcomes. Although postoperative isometric trunk flexion strength (ITFS) has previously been investigated, the results were based on measurement tools distinguished by poor reproducibility and validity. OBJECTIVE: To evaluate the reproducibility of and variations in ITFS following abdominal surgery using a dynamometer and explore the correlation between ITFS and the scar length. METHOD: The study group consisted of 22 consecutive patients (15 men and 7 women) referred for surgery. The outcome parameters included ITFS which was measured using a fixed dynamometer and a digital manometer, scar length, weight and pain. Test-retest measurement (3 h apart) of ITFS was taken 1 day before surgery to determine the instruments' reproducibility. Additional measurements of the outcome parameters were taken 1 and 6 weeks postoperatively. RESULTS: Excellent test-retest correlations (ICC > 0.85) coupled with low standard error of the measurement for both the ITFS and the manometric findings indicated clinically acceptable reproducibility of the findings. Significant pre- and postoperative differences in ITFS were noted using both techniques. Six weeks postoperatively, fair and significant correlations were noted between the dynamometry-based ITFS and both the scar length (r = 0.452) and age (r = 0.498). Of note, scar length and preoperative dynamometric ITFS predicted ITFS 6 weeks postoperatively (F = 102.949, p < 0.001, R(2) = 0.92). CONCLUSIONS: Measurements of ITFS using dynamometry in elective CRC patients are reproducible, sensitive to clinical changes and allow prediction of postoperative ITFS scores based on their preoperative counterparts.

Isokinetic assessment of the shoulder rotators: a study of optimal test position.

BACKGROUND: Isokinetic assessment of the shoulder rotator cuff is a common component of shoulder muscles assessment. Nevertheless, the extensive mobility of the shoulder poses great difficulty in finding a consensus protocol for evaluation. OBJECTIVE: To select an optimal protocol, among three, based on the best reproducibility and reliability of strength scores derived from internal and external rotator tests. METHOD: The dominant side external and internal rotator muscles of twelve healthy male subjects were evaluated based on a concentric protocol (60° s(-1) and 240° s(-1) ) in three different test positions: two in lying supine with the arm in either 90° or 45° abduction and one in the seated position with the arm moving in the scapular plane on the dominant shoulder. Subjects were tested twice over 10 days. RESULTS: The two lying installations were associated with the lowest coefficient of variation (7.1-11.8%) and smallest detectable difference (7-15.9 N.m) for peak moment and strength ratios. Consequently, the lying positions were chosen for rotators assessment with 90° of abduction associated with a higher reproducibility for the agonist/antagonist ratios or 45° if some pain was provoked. In any case, the coefficient of variation did not exceed 12%. CONCLUSION: Based on a reproducibility and reliability analysis, we recommend the testing of isokinetic strength of the shoulder rotators to be conducted in supine lying, with the arm at 90° or 45° abduction in the frontal plane.

Effect of a cognitive task on postural control in patients with a clinically isolated syndrome suggestive of multiple sclerosis.

BACKGROUND: Patients with multiple sclerosis (MS) frequently experience poor postural control affecting mobility and/or cognitive impairment, even in the early stages of the disease. As postural control consumes attentional resources, it is essential to test stability during a cognitive task. AIM: To assess postural control and determine the effect of a cognitive task on balance in patients with a clinically isolated syndrome (CIS) suggestive of MS, within 3 months from onset. DESIGN: Observational case control study SETTING: Multiple Sclerosis Center and Institute of Motor Functions, Sheba Medical Center, Tel Hashomer, Israel POPULATION: Fifty-two CIS patients, aged 35.2±1.3 years, disease duration of 54±6.2 days and Expanded Disability Status Scale (EDSS) of 1.7±0.2, participated in the study. The control group consisted of 28 age and gender matched healthy subjects. METHODS: Stability was evaluated by the quantifying movement of the center of pressure (CoP) during standing under three conditions: eyes open, eyes closed, and while performing the modified Stroop test. Sway rate and CoP data was collected by a computerized force platform device. RESULTS: After combining major postural control parameters, only 50% of the patients performed normally. Differences in postural variables were found between patients and healthy subjects (P<0.01). Both sway rate and standard deviation of the CoP in all test conditions were significantly higher in patients compared to controls. The cognitive task resulted in an elevated sway rate both in CIS patients and the control group when compared with the eyes open task. Within 3 months of the onset of neurological symptomatology, postural instability was detected in 50% of CIS patients using a dedicated balance measurement device. CONCLUSION: As these findings are associated with the very early phase of MS, it appears that the ongoing pathological disease process is already taking place with regard to the balance control system. CLINICAL REHABILITATION IMPACT: Identification of postural abnormalities in the early stages is important in order to establish proper intervention programs.

Epilepsy syndrome-associated balance dysfunction assessed by static posturography.

PURPOSE: To compare subclinical balance dysfunction in patients with various epilepsy syndromes with apparently healthy subjects. METHODS: Twenty-seven patients with localization-related epilepsy (LRE), 19 with primary generalized epilepsy (PGE), who had no subjective complaints of impaired balance and no abnormal neurologic findings on examination, and 22 apparently healthy subjects, underwent static posturography using the Posture Scale Analyzer (PSA) system. RESULTS: Sway index was higher in patients compared to healthy subjects in all tests, significant for single leg stance (p=0.005). Patients with PGE had a higher sway index compared to patients with LRE in six of the tests, also significant for single leg stance (p=0.027). This difference was not affected by the type of AED treatment or disease duration. CONCLUSION: Posturography can improve balance function assessment in patients with epilepsy, demonstrate subclinical impairment in seemingly asymptomatic patients, and further characterize balance deficits in different epilepsy syndromes.

Physical activity participation and bleeding characteristics in young patients with severe haemophilia.

Patients with haemophilia are now widely advised to participate in sport activities. However, no extensive data are available about their actual participation. The aim of this study was to describe the type; intensity and duration of leisure time physical activity (PA) among young patients with severe hemophilia and to assess whether there are differences in bleeding profile and muscle strength in related to activity intensity. Forty-four boys (ages 12-25 years) with severe haemophilia were studied. PA was assessed by the Godin and Shephard (G&S) questionnaire. Bleeding profile was determined based on a one month diary filled by each patient. Muscle strength of the lower limbs muscles was assessed using a hand held dynamometer. Only three subjects did not perform any PA. Twenty-five of the participants performed strenuous PA at least once a week. An inverse, moderate association (r(p) =-0.45, P < 0.002) was found between the G&S score and age. There were no significant differences in bleeding frequency or pain but a significant difference in the cause of bleed was found: those who exercised strenuously showed a higher proportion of bleeds due to traumatic reasons (P < 0.01). No differences in muscle strength values were noted in related to activity intensity also no linear association was noted between muscle strength and bleeding profile. Further investigation, including prospective studies, is needed in order to assess the temporal sequencing between training and the occurrence of bleeds and bleeds cause.

Quadriceps and hamstring isokinetic strength and electromyographic activity measured at different ranges of motion: a reproducibility study.

Isokinetic strength measurements of the quadriceps and hamstring that are commonly conducted using a 90 degrees range of motion (RoM) may involve some risk to specific knee patient groups. Testing these muscles at a much shorter RoM may reduce the risk but in order to render this method clinically acceptable the reproducibility of the derived test findings has to be established. Therefore the main objective of this study was to assess the reproducibility of isokinetic peak torque and normalized EMG scores of these muscles based on 90 degrees (0-90 degrees flexion, LR) and three successive short RoMs: 0-30 degrees (SR1), 30-60 degrees (SR2) and 60-90 degrees (SR3). Eight healthy subjects were tested three times with a 2 week between-session interval. All tests were performed on the dominant limb and consisted of maximal concentric and eccentric exertions. The velocities applied were 90 degrees /s for LR and 30 degrees /s for each of the SRs. Findings indicated no between-session improvement in strength. Based on the coefficient of variation the measurement error for all isokinetic strength scores remained stable throughout the testing sessions ranging 0.6-13.9% with the absolute majority of instances less than 10%. The reproducibility of the EMG scores was poorer ranging 1.5-25% and 0.5-19% for the quadriceps and hamstring, respectively. It is concluded that testing of knee muscles at short (30 degrees ) RoMs does not compromise the reproducibility of the strength or EMG scores derived from the commonly used RoM of 90 degrees . However, whereas strength was reproducible to within the accepted clinical standards, the corresponding EMG scores were characterized by a wider error band.

Testing knee extension and flexion strength at different ranges of motion: an isokinetic and electromyographic study.

The main objective of this study was to explore the mechanical and electrical output of thigh muscles derived from a range of motion (RoM) of 90 degrees (0-90 degrees flexion, LR) and the three successive RoMs: 0-30 degrees (SR1), 30-60 degrees (SR2) and 60-90 degrees (SR3). Thirteen men took part in the study. In view of the torque-velocity relationship and in order to render the test conditions as equivalent as possible, LR was tested at 90 degrees /s while the corresponding velocity for all SRs was 30 degrees /s. The findings indicated very good agreement between LR and SR2 in terms of absolute strength (particularly the concentric), within muscle eccentric to concentric strength ratios, between muscles (agonist to antagonist) strength ratios and the normalized IEMG (expressed in muV/Nm). An agreement was also noted between the mean eccentric peak torque of the knee flexors at LR and SR1 and between the mean eccentric peak torque of the knee extensors at LR and SR3. However, in general there was a lesser agreement between LR and SR1 or SR3. It is suggested that testing thigh muscles in the middle sector of knee motion (SR2) yields strength and EMG data that are close and well correlated with those derived from testing the knee along the commonly used (0-90 degrees ) RoM.

Electro-oculographic measures in patients with chronic whiplash and healthy subjects: a comparative study.

BACKGROUND: Despite their high incidence, costs, and long lasting disability, whiplash associated disorders (WAD) lack an identifiable objective pathology that explains their acute or chronic symptoms. OBJECTIVE: In view of previous suggestions of a possible effect of neck torsion on several electro-oculography (EOG) parameters, the main objective of this study was to examine their applicability in differentiating patients from uninvolved subjects. METHODS: Smooth pursuit and saccadic eye movements were assessed in 26 patients with chronic WAD and 23 healthy subjects. All tests were executed in three neck positions: neutral and rotations to left and right. RESULTS: Neck torsion did not influence eye movement performance of either the WAD or healthy groups. However, compared with the healthy group, patients with WAD had significantly lower smooth pursuit velocity gain (SPVG) (p = 0.01) and prolonged saccadic latency (p = 0.001), irrespective of neck position. CONCLUSIONS: Despite scattered differences that reached significance, the electro-oculographic measures used in this study do not seem to offer a clinically relevant method for differentiating between patients with WAD and normal subjects.

Cervical circumduction in normal subjects: a study of maximal versus feigned effort.

The feasibility of using the coefficient of variation in conjunction with motion parameters derived from head circumduction to obtain a compact criterion for differentiating maximal from feigned cervical motion was evaluated. Twenty-five healthy subjects were measured twice during a period of 3 weeks using an ultrasonography-based motion analysis system. Subjects were asked to produce maximal motion of the spine as well as to feign limitation. Extracted from the displayed traces of head circumduction, the angular values of the primary motions of flexion, extension, right and left lateral flexion, as well as their additive score (AS) were determined. No test-retest differences were indicated. The average range of motion (ROM) was significantly smaller and the coefficient of variation of the ROM was significantly larger in the feigned compared with the maximal performance in both tests. However, tolerance interval analysis indicated that the coefficient of variation could not effectively separate between the effort levels, being particularly deficient with respect to AS. In addition, a differential sensitivity in identifying false-negative cases as a function of the movement paradigm was revealed. This study indicates that in healthy subjects, the use of a complex cervical movement such as circumduction cannot serve for differentiating between maximal and feigned performance using the coefficient of variation. The results may also point out the existence of a mechanism for adjusting proportional reductions among the primary cervical motions that result in excellent repeatability even in feigned efforts.

Maximal versus feigned active cervical motion in healthy patients: the coefficient of variation as an indicator for sincerity of effort.

STUDY DESIGN: Maximal and submaximal (feigned) cervical motions in healthy patients were compared. OBJECTIVE: To test the efficiency of the coefficient of variation in differentiating maximal (sincere) from submaximal (feigned) cervical motion in healthy patients. SUMMARY OF BACKGROUND DATA: Although limitation of cervical motion is a recognized impairment, no well-founded approach for verifying the degree to which a patient is maximizing his or her performance is available currently. METHODS: A new ultrasound-based system for three-dimensional motion analysis of the head was used to test 25 healthy patients (22 women and 3 men) ages 26 to 48 years. During the first test, (Test 1), the patients were asked initially to move the head maximally at a self-determined velocity in all the primary directions: flexion, extension, right and left rotation, and right and left lateral flexion. They then were presented with a short vignette describing a fictitious accident and asked, using the same protocol, to perform the same types of cervical motions as if they had experienced an injury. No further instructions were provided. A retest (Test 2) in reverse order (feigned effort first) took place 1 to 16 weeks (mean, 3.3 weeks) later. RESULTS: The range of motion and average velocity were significantly smaller (P = 0.0001) in the feigned than in the maximal performance in all directions and on both tests. Feigned range of motion and velocity also were significantly reduced in Test 2 (P = 0.006), as compared with those in Test 1 (P = 0.0001). The range of motion coefficient of variation in the feigned performance (CVf) remained stable on the retest, but was significantly larger on both tests (P < 0.001) than the corresponding CV derived from maximal performance (CVm). Furthermore, a case-by-case analysis showed that whereas the American Medical Association guidelines identified only 16% of the feigned cases, the use of CVf and CVm resulted in a corresponding rate of 87%. Tolerance intervals at 95% and 99% indicated total separation between the distributions of CVf and CVm, respectively. The average velocity-based CVf and CVm were not of a comparable differentiating power. CONCLUSIONS: This study indicates that in healthy patients, feigned performance may be differentiated from maximal (sincere) performance effectively and reproducibly using the coefficient of variation.

Reproducibility and validity of a new test protocol for measuring isokinetic trunk extension strength.

OBJECTIVE: To investigate the reproducibility and validity of isokinetic trunk extension strength scores obtained using a range of motion of 20 degrees and velocities of 10 and 40 degrees /s. BACKGROUND: Common protocols for testing trunk extension strength incorporate a range of motion of 40 degrees or more and test velocities of between 30 and 180 degrees/s. These test parameters may be neither necessary for portraying the strength profile of the muscles involved nor suitable for patients impaired with low back dysfunction. DESIGN: Test-retest of maximal concentric and eccentric isokinetic trunk extension strength in healthy subjects. METHODS: 17 women and 18 men were tested twice within 1-2 weeks. Tests were performed with subjects positioned in sitting. RESULTS: The trunk extension strength scores revealed excellent agreement with the expected physiological moment-velocity curve. On average women's trunk extension strength was 62% that of men (range: 59.3-64.4%). The test-retest correlation coefficients were generally higher in women (0.70-0.87) than in men (0.52-0.78) and significant at P=0.01. The standard error of measurement ranged between 13 and 21 N m for women and between 35 and 50 N m for men, which were equivalent to 9% and 15% of the mean strength in women and men, respectively. CONCLUSION: This study indicates that the present protocol may be validly applied in assessing trunk extension strength in normal women. RELEVANCE: Reproducible and valid trunk extension strength findings are essential if measurable strength deficiency of the extensors is to be formally accepted as an impairment. The present protocol incorporates or meets most of the relevant problems associated with trunk concentric and eccentric strength testing, and hence has the potential of becoming a standard method for clinical applications.

Identifying feigned isokinetic trunk extension effort in normal subjects: an efficiency study of the DEC.

STUDY DESIGN: A test-retest comparison of maximal and feigned trunk extension effort in normal subjects was performed. OBJECTIVE: To test the robustness of an index termed DEC for differentiating maximal from feigned effort in normal subjects. SUMMARY OF BACKGROUND DATA: Previous studies have indicated that the DEC, which is the difference between the eccentric to concentric strength ratio at two test velocities, is a powerful identifier of feigned effort. This has been found for various muscle groups including the trunk extensors. However, whether this efficiency is affected by exposure to the protocol, learning, or other factors had not been examined. METHODS: Using a KinCom isokinetic dynamometer, 18 men and 17 women were tested twice within 1 to 2 weeks. Concentric and eccentric efforts of the trunk extensors were exerted using a short range of motion (20 degrees ) and two test velocities (10 degrees and 40 degrees per second). In the first part of each test, participants exerted maximal force against the lever arm, whereas in the second part they were to feign their maximal capability, pretending the presence of injury. RESULTS: In both Tests I and II, the feigned DEC scores (DECf) of all the participants were greater than the maximal DEC (DECm) scores (P = 0.0001). Repeated measurement analysis showed that neither DECm nor DECf varied systematically from Test 1 to Test 2. On the basis of the individual male scores, the DEC cutoff score of 0.41 was 100% efficient in Test 1 at differentiating feigned from maximal effort, with neither false-positive nor false-negative cases. Test 2 had a single false-positive case (efficiency 95%), and the optimal cutoff score was 0.275. In the female group, the corresponding efficiency of the DEC was 82% (optimal cutoff, 0.35) for Test 1 and 70% (optimal cutoff, 0.25-0.35) for Test 2. A statistical model for tolerance intervals at 90%, 95% and 99% indicated higher cutoff values for women than men. CONCLUSION: In healthy subjects, the DEC effectively differentiates feigned from maximal performance.

Reproducibility and instrument validity of a new ultrasonography-based system for measuring cervical spine kinematics.

OBJECTIVE: To report instrument validity of CMS 70P, a new ultrasonography-based system for spatial kinematic analysis of the spine and its application in studying the reproducibility of cervical motion findings in healthy subjects. BACKGROUND: Reproducibility of cervical motion has been investigated using various instruments and consisting in most cases of short test-retest time intervals of between minutes to days. METHODS: Performance of the instrument was validated against a digital inclinometer, at ranges of motion compatible with actual cervical motion. To study reproducibility, 25 healthy individuals, 22 women and 3 men aged 26-48 were tested twice within an average time interval of 3.3 weeks. Performed in the seated position and at a self-determined pace, cervical motion was defined in terms of head motion relative to a sternal (reference) system, in all six primary motions: flexion, extension, right rotation, left rotation, right lateral flexion and left lateral flexion. RESULTS: The system exhibited excellent agreement with the digital inclinometer, establishing its instrument validity for testing cervical motion. No significant differences were indicated between the test and retest for both the net maximal displacements and average velocities. The correlation coefficients for the single plane motions (e.g. flexion+extension) were higher than those derived for the primary motions, and ranged between 0.78 (sagittal plane) and 0.88 (frontal plane). The magnitude of the standard error of the measurement reflected the same trend with the lowest value recorded for the frontal plane. The self-selected velocity at which these motions were performed was similar in the frontal and saggital planes but was significantly higher for the transverse plane (rotations). CONCLUSIONS: This study indicates that spanned over time intervals that are measured in weeks, cervical motion findings derived from the CMS 70P are well reproducible. Findings also imply the need for a more stringent control of subject positioning and stabilization. RELEVANCE: Reduction of range of motion and average is typically observed in various pathologies of the cervical spine and is regarded, together with pain, as a major impairment. Therefore, valid assessment of cervical motion which is essential for follow-up and treatment outcome strongly depends on reproducibility of the findings. This study indicates that acceptable reproducibility is maintained over periods of time which are clinically meaningful using the system described herewith.

EMG and strength correlates of selected shoulder muscles during rotations of the glenohumeral joint.

OBJECTIVE: To identify activation patterns of several muscles acting on the shoulder joint during isokinetic internal and external rotation. DESIGN: Combined EMG and isokinetic strength analysis in healthy subjects. BACKGROUND: EMG studies of the shoulder region revealed intricate muscular activation patterns during elevation of the arm but no parallel studies regarding pure rotations of the joint could be located. METHODS: Fifteen (n=30 shoulders) young, asymptomatic male subjects participated in the study. Strength production during isokinetic concentric and eccentric internal and external rotations at 60 and 180 degrees /s was correlated with the EMG activity of the rotator cuff, biceps, deltoid and pectoralis major. Analysis of the smoothed EMG related to the timing of onset of the signal and to the normalized activity at the angle of the peak moment. Determination of the association between the EMG and the moment was based on strength ratios. RESULTS: Findings indicated that for both types of rotations, the rotator cuff and biceps were active 0.092+/-0.038-0.215+/-0.045 s prior to the initiation of the actual movement and 0.112-0.034 s prior to onset of deltoid and pectoralis major activity. These differences were significant in all of the eight conditions (P<0.05). In terms of the strength ratios, strong association was found between electrical activity and moment production in the subscapularis and infraspinatus (r(2)=0.95 and 0. 72, respectively) at the low and high angular velocities. CONCLUSIONS: Prior to actual rotation of the shoulder joint, normal recruitment of the rotator cuff and biceps is characterized by a non-specific presetting phase which is mainly directed at enhancing the joint 'stiffness' and hence its stability. Once movement is in progress, the EMG patterns of these muscles become movement specific and are correlated with the resultant moment. RELEVANCE: Muscular dysfunction relating to delayed onset activity or altered activation patterns, due to pain, perturbed mechanics or disturbed neural activation have been implicated as concomitant factors in other joint associated pathologies. Through highlighting the role of the rotator cuff in shoulder joint rotations, this study lends further support to the argument that a parallel situation may prevail with respect to shoulder joint dysfunction. This could lead to the development of rehabilitation protocols aimed specifically at redressing such dysfunction.

Identification of feigned grip effort using isokinetic dynamometry.

OBJECTIVE: To investigate the feasibility of applying isokinetic dynamometry for identifying submaximal grip strength. DESIGN: Measurement of maximal and feigned concentric and eccentric strength at high and low contraction velocities. BACKGROUND: Identification of feigned grip strength is a highly problematic issue which has been challenged using various techniques, invariably related to isometric efforts. This study is based on recent research which has indicated that isokinetic dynamometry was highly efficient in identifying feigned efforts in other major muscle groups. METHODS: Seventeen healthy women aged 20-25 took part in the study. Prior to executing the feigned effort, subjects were told to exert lower than the maximal grip strength in an attempt to obtain financial compensation for a simulated injury to hand musculature which in fact did not result in weakness of grip. RESULTS: Findings indicated that based on a parameter termed DEC which was defined as the difference between the ratios of the eccentric to concentric strength at the high and low velocities, feigned efforts could very effectively be identified (P<0.0001). Furthermore, a multivariate model enabled this identification to be described in terms of the level of confidence by which a claim concerning weakness of grip may be proclaimed as genuine or insincere. CONCLUSIONS: Though the neuromotor mechanisms responsible for grip strength may differ from those acting with respect to other muscle groups, the inability to adjust the eccentric and concentric force components during submaximal efforts is probably a general feature. RELEVANCE: Isokinetic dynamometry is a powerful method for quantifying various aspects of muscle performance. However, its application in the medicolegal area of muscle weakness has only recently been explored. Combined with previous research, this study strongly indicates that if certain trauma or pathology-related weakness does not result in variations in the force-velocity characteristics of the affected muscles, than this technique has the potential to validly differentiate between patients who have a genuine reason for compensation and those ('symptom magnifiers') who do not.