Age-specific differences in the time-frequency representation of surface electromyographic data recorded during a submaximal cyclic back extension exercise: a promising biomarker to detect early signs of sarcopenia.

PURPOSE: Motivated by the goal of developing new methods to detect early signs of sarcopenia, we investigated if surface electromyographic (SEMG) data recorded during the performance of cyclic, submaximal back extensions are marked by age-specific differences in their time and frequency characteristics. Furthermore, day-to-day retest reliability of the EMG measures was examined. METHODS: A total of 86 healthy volunteers used a back dynamometer to perform a series of three maximal voluntary contractions (MVC) consisting of isometric back extensions, followed by an isometric back extension at 80% MVC, and finally 25 slow cyclic back extensions at 50% MVC. SEMG data was recorded bilaterally at L1, L2, and L5 from the iliocostalis lumborum, longissimus, and multifidus muscles, respectively. Tests were repeated two days and six weeks later. A linear mixed-effects model with fixed effects "age, sex, test number" and the random effect "person" was performed to investigate age-specific differences in both the initial value and the time-course (as defined by the slope of the regression line) of the root mean square (RMS-SEMG) values and instantaneous median frequency (IMDF-SEMG) values calculated separately for the shortening and lengthening phases of the exercise cycles. Generalizability Theory was used to examine reliability of the EMG measures. RESULTS: Back extensor strength was comparable in younger and older adults. The initial value of RMS-SEMG and IMDF-SEMG as well as the RMS-SEMG time-course did not significantly differ between the two age groups. Conversely, the IMDF-SEMG time-course showed more rapid changes in younger than in older individuals. Absolute and relative reliability of the SEMG time-frequency representations were comparable in older and younger individuals with good to excellent relative reliability but variable absolute reliability levels. CONCLUSIONS: The IMDF-SEMG time-course derived from submaximal, cyclic back extension exercises performed at moderate effort showed significant differences in younger vs. older adults even though back extension strength was found to be comparable in the two age groups. We conclude that the SEMG method proposed in this study has great potential to be used as a biomarker to detect early signs of sarcopenic back muscle function.

A systematic review on the effectiveness of medical training therapy for subacute and chronic low back pain.

Medical training therapy (MTT) to improve muscular strength and endurance follows evidence based guidelines and is increasingly recommended to patients suffering from subacute and chronic back pain (LBP). This study investigated whether MTT was effective in reducing pain and improving function in patients with subacute or chronic LBP. Data sources were MEDLINE, EMBASE, CINAHL, Pedro, Cochrane Central Register of Controlled Trials. We included RCTs that examined exercise or MTT in adult patients with LBP compared to placebo, no intervention or other interventions. Study outcomes had to include at least one of the following: pain intensity; functional status, absenteeism. Two independent reviewers performed quality assessment. Visual analogue scale ratings ranging from 0-10 MTT quantified the MTT aspects of the intervention. Studies with rating scores >7.5 were included. We identified only 2 studies that examined the effectiveness of MTT. Both trials, one was of high quality, found MTT to decrease pain and improve function significantly better than therapy of uncertain effectiveness. There is moderate evidence that would support the effectiveness of MTT in the treatment chronic LBP. Future high quality RCT will have to clarify whether MTT is effective and would be superior to other forms of therapeutic exercise.

Risk assessment after hip fracture: check the "healthy" leg!

BACKGROUND AND AIM: Functional deficits may increase the risk for further falls after hip fracture. The aim of this study was to elucidate function and range of movement (ROM)-related risk factors. METHODS: The consecutive, prospective study included all patients admitted to the rehabilitation unit. The geriatric assessment was performed after admission and before discharge; ROM was measured using the neutral zero method. Falls, defined as unintentionally coming to rest on the floor, were documented. Patients' functions were analyzed comparing fallers to nonfallers. RESULTS: A total of 1,497 patients with a mean age of 81.1 ± 8.2 years were included. The incidence of falls during rehabilitation was 9.6 per 1,000 patient-days and was related to patients' age: patients younger than 75 years had an incidence of falls of 5.0, those between 75-84 years had an incidence of 9.5, and those >84 years had an incidence of 12.0, respectively. Fallers showed significantly more functional deficits both in the operated and on the nonoperated leg. Using logistic regression models, especially ROM measured in the frontal plane (hip adduction and abduction) of the nonoperated hip was significantly associated with an increased risk of falling (OR 0.986, 95% CI 0.973-0.999, p = 0.037). CONCLUSION: Patients are at high risk for falls after hip fracture, with age itself being one of the most dominant risk factors. In addition to previously identified gait and mobility disorders, the physical limitations of arthritis of the "healthy" hip seem to be responsible for the functional decline. Therefore, it would be of interest to include the examination of the hips into a falls risk assessment battery.

[Evidence-based medicine and therapeutic ultrasound of the musculoskeletal system]. / Evidenzbasierte Medizin und Ultraschalltherapie des Skeletts.

The aim of this review is to critically analyze the evidence of therapeutic ultrasound between 0.8 and 3 MHz for treating musculoskeletal diseases. Relevant randomized, controlled, clinical trials and systematic reviews published on this topic have been taken into consideration.There was evidence of effectiveness for the following indications: inflammatory and degenerative diseases of joints and the vertebral column, overuse syndromes of tendons and muscles and the facilitation of bone tissue healing.According to the current knowledge an evidence-based recommendation could be most clearly made for the facilitation of bone fracture healing with ultrasound. For all other indications evidence was based on overly sparse data from low quality randomized controlled trials that would not allow clear recommendations. However, there is also a lack of data from methodologically sound clinical trials that could have proven the inefficacy of this treatment. As beneficial effects with ultrasound are frequently observed in everyday clinical practice, this therapeutic modality should continue to be considered in the future as a treatment option for musculoskeletal diseases.

Reliability of posturographic measurements in the assessment of impaired sensorimotor function in chronic low back pain.

UNLABELLED: The evaluation of postural stability using posturography could be both a valuable functional diagnostic and treatment outcome monitoring tool in rehabilitation practice of patients with chronic low back pain (cLBP). No evidence, however, seems to exist, whether or not such posturographic measures are reliable in these patients and therefore clinically and scientifically useful. The aims of this study were manifold and aimed at investigating (1) differences of posturographic measures between cLBP patients and healthy controls (HCs), (2) short- (intrasession-) and long-term (intersession-) reliability of these measurements, and (3) the relationship between both pain intensity and test-related feelings and significant learning effects of the posturographic measures in cLBP. A total of 32 cLBP patients and 19 non-sportive HCs completed (1) comprehensive clinical examination, (2) quantitative posturographic testing (SMART EquiTest, Neurocom International, Clackamas, Oregon) that included all the sensory organisation test (SOT), the motor control test (MCT) and the adaptation test (ADT) and (3) psychological ratings of pain as well as posturographic test related personal feelings and fear associated beliefs. Of these, 22 cLBP patients who received no therapy repeated all measurements and examinations on a second day, 2-3 weeks later. Results revealed significant differences between cLBP patients and HCs in the more demanding postural test conditions of the SOT and the SOT composite score only. Intra-session reliability testing demonstrated significant improvements of the SOT and ADT measures for both HCs and cLBP patients. Results of long-term reliability testing showed significant improvements of the more challenging SOT conditions and SOT composite score. VAS ratings of pain, feelings and fear associated beliefs were not associated with such longitudinal changes. CONCLUSION: Our findings suggest that the significant learning effects observed for the SOT conditions may limit the clinical application of SMART EquiTest postural stability measures for cLBP patients in rehabilitation everyday practice. Further development in software processing will be necessary to identify new postural parameters that are less prone to learning effects.

Postural control during lifting.

Any voluntary motion of the body causes an internal perturbation of balance. Load transfer during manual material handling may increase these perturbations. This study investigates effects of stance condition on postural control during lifting. Nineteen healthy subjects repeatedly lifted and lowered a load between a desk and a shelf. The base of support was varied between parallel and step stance. Ground reaction force and segmental kinematics were measured. Load transfer during lifting perturbed balance. In parallel stance postural response consisted of axial movements in the sagittal plane. Such strategy was accompanied by increased posterior shear forces after lift-off. Lifting in step stance provided extended support in anterior/posterior direction. The postural control mechanisms in the sagittal plane are less complex as compared to parallel stance. However, lifting in step stance was asymmetrical and thus accompanied by distinct lateral transfer of the body. Lateral shear forces were larger as compared to parallel stance. Both lifting techniques exhibit positive and negative aspects. We cannot recommend either one as being better in terms of postural control.

Reliability of pelvic floor muscle strength measurement in elderly incontinent women.

Pelvic floor muscles (PFM) play an important role in maintaining urinary continence with increasing age. Therefore, their contractile properties need to be evaluated. The aim of the study was to examine the reliability and correlation of simple techniques to measure PFM strength in elderly women with urinary incontinence. An interview was used to evaluate the ability to stop the urinary stream during micturition and to calculate the incontinence index. A pad test was applied to objectively evaluate the severity of the disease. Functional testing included a digital examination to measure the force and duration of one contraction, a perineometer measurement (Peritron) to assess maximal contraction force and contraction force of 5 s, and a cone-retention test (Femcon) while walking for 1 min and during Valsalva's manoeuvre. This procedure was performed on three separate occasions within one week. The 37 participating women with a mean age of 62+/-8 (mean+/-SD) years had a severity index of 4.4+/-2.6 and a urine loss of 9.5+/-13.6 mg during the pad test. Sixteen women were able to completely stop the urinary stream during micturition. The digital examination showed no intratester variability. The perineometer measurement showed that the absolute difference in maximal contraction force and mean contraction force within 5 s was less than 5.3 mm Hg and 4.5 mm Hg, respectively, with a probability of 0.95. While walking and during Valsalva's manoeuvre, 19 and 20 women, respectively, held the same cone in place on all three occasions. The maximal contraction force and mean force during the 5-s contraction correlated well with the ability to stop the urinary stream and the digital examination but only weakly with the cone-retention tests. The reliability of PFM strength measurement is highest in the digital examination, followed by perineometer measurements, and then by vaginal cone tests. As PFM function is easy to assess, it should be routinely done in the assessment of urinary incontinence in elderly women.

Sensory-motor control of the lower back: implications for rehabilitation.

Although low back pain (LBP) is a widespread and disabling health problem, there is a lack of evidence based medicine with respect to its treatment and rehabilitation. A major reason for this is the poor understanding of the underlying mechanisms of the LBP syndromes. In an attempt to fill this gap, the present review article provides an overview of the sensory-motor control aspects of trunk stabilization and postural control of the trunk, and how they may relate to the evolution of LBP. In particular, the anatomy and physiology of the sensory-motor control mechanisms of the trunk muscles that contribute to general and segmental stability of the lumbar spine will be elucidated. Furthermore, a brief overview of current theories of postural control will be provided with respect to spinal stabilization. Finally, a concept of the pathophysiological changes within the sensory-motor control mechanisms of the lumbar spine in the presence of muscle injury and pain will be presented. The impact of pain and muscle injury on the muscular support for the lumbar motion segment will be discussed along with the deficits in neuromuscular control in LBP patients with decreased segmental lumbar stability.

The effect of calisthenic home exercises on postmenopausal fractures--a long-term observational study.

OBJECTIVES: To evaluate the long-term effects of calisthenic home exercises on the incidence of fractures in postmenopausal women. DESIGN: Controlled long-term observational study. METHODS: Postmenopausal women between 45 and 75 years of age who had been randomly assigned to an exercise or control group in the course of a previous study conducted 5-10 years ago, were invited for follow-up. The number of fractures before and during the observation time were recorded by means of a questionnaire. Vertebral deformities due to fractures were diagnosed by X-rays at entry and at follow-up. Walking speed, muscle strength, static posturography, and maximum oxygen uptake were measured in addition. RESULTS: After an average follow-up time of 7.6+/-1.1 years, 73 women of the exercise group and 64 subjects of the control group were investigated. Thirty-three per cent (n=24) of the exercise group reported to have exercised continuously at least three times a week for 20 min. No intergroup differences between the compliant and non-compliant exercisers and the control group were seen in the number of fractures. However, the incidence of fracture was lowest in women with a baseline bone mass less than one standard deviation (SD) below the mean for young adults (high BMC) and highest in those with more than 2.5 SD below the mean for young adults (low BMC) (P<0.001, odds ratio 2.9 [95% CI, 1.59-5.39]). CONCLUSION: This long-term follow-up did not produce any evidence that prescription of a calisthenic home exercise program may prevent fractures in postmenopausal women aged between 61+/-6.4 and 68+/-6.5 years.

Effectiveness of exercise therapy in patients with internal derangement of the temporomandibular joint.

This study intended in evaluating the effectiveness of exercise therapy in patients with craniomandibular disorders (CMD). Twenty consecutive patients suffering from CMD with anterior disc displacement without reduction consulting a CMD service were included in the study if they met following criteria: (i) pain in the temporomandibular region, (ii) reduced incisal edge clearance (<35 mm), (iii) magnet resonance imaging confirmed anterior disc displacement without reduction and (iv) evidence of postural dysfunction. All patients were assigned to a waiting list, serving as a no-treatment control period, according to a before-after trial. The treatment consisted of active and passive jaw movement exercises, correction of body posture and relaxation techniques. A total of 18 patients completed the study, no adverse effects occurred. Following main outcome measures were evaluated: (1) pain at rest (2) pain at stress (3) impairment (4) mouth opening at base-line, before and after treatment and at 6 month follow-up. As a result of treatment pain, impairment and mouth opening improved significantly more than during control period (paired samples t-test P < 0.05). After treatment four patients had no pain at all (chi-square: P < 0.05) and only seven patients revealed an impaired incisal edge clearance after treatment. (chi-square Test, P < 0.001). At follow up, seven patients had no pain and experienced no impairment. Exercise therapy seems to be useful in the treatment of anterior disc displacement without reduction.

Effects of back extensor strength training versus balance training on postural control.

PURPOSE: Aim of this study was to investigate effects of 1) regular back extensor strength training as opposed to balance training, and 2) the influence of the sequence of both training types on postural control, force, and muscle efficiency. METHODS: Twenty-six young, healthy subjects were investigated at baseline, 1 month and 2 months later. At each examination, subjects completed a posturographic, balance skill, and isometric maximum voluntary (MVC) back extension testing, including surface electromyographic (SEMG) recordings. After baseline evaluation, subjects were assigned to either daily strength training or balance training. After 1 month, the type of training was exchanged between groups. RESULTS: After 1 month, back extensor strengthening led to decreased postural stability on hard surface, whereas there were no change after balance skill training. Analysis of the low- and high-frequency components of the sway signal revealed that strength training increased control efforts as indicated by an increased high-frequency component in order to maintain postural stability and unchanged low-frequency component. Balance skill training, however, increased postural stability as indicated by a decreased low-frequency component. The control effort remained unchanged. After completing either sequence of training, all postural parameters remained unchanged in both groups. Muscular efficiency as measured by SEMG root mean square during a standardized motor skill task revealed improved muscle economy regardless of the type of training. Back extension torque improved in both groups. CONCLUSION: To avoid reduction of postural stability in rehabilitation processes, we recommend to include antagonist muscles in a comprehensive strength training regime or balance skill training.

Load-dependence of fatigue related changes in tremor around 10 Hz.

OBJECTIVES: The aim of the study was to investigate the effects of different loads on tremor around 10 Hz during fatiguing contractions. METHODS: Eighteen healthy volunteers performed sustained isometric knee extensions at 30%, 50% and 70% maximum voluntary contraction (MVC). During the fatiguing contractions, mechanical recordings were made with a high-resolution force sensor. Tremor-power was calculated for the 6-20 Hz frequency window as a function of time normalized to endurance time. RESULTS: Initial tremor power was different between the high and low load tasks. Changes of tremor with contraction time differed between the three tasks, in that tremor of the 30% MVC contraction showed the least decrease throughout the sustained contraction, whilst that of the 50% and 70% MVC showed progressively higher decreases. At failure, all 3 contractions merged to the same tremor level. CONCLUSION: Load-dependent, fatigue-related 6-20 Hz tremor changes during sustained submaximum voluntary contractions seem mainly the consequence of recruitment of new units and fatigue-related properties of the high threshold motor units of muscles.

Aerobic capacity in adult dermatomyositis/polymyositis patients and healthy controls.

OBJECTIVE: Assessment of myositis patients has relied on symptoms, strength testing, and serum muscle enzyme activity. Recently, functional assessments and evaluation of strength by dynamometry and of disease activity by magnetic resonance imaging have also been added. Aerobic testing in selected patients has been considered useful. DESIGN: Case-control study. SETTING: University Hospital, Vienna, Austria. PATIENTS: Twenty-two subjects (8 outpatients with chronic dermatomyositis and 3 outpatients with chronic polymyositis, and 11 healthy controls) participated, allowing the identification of 11 case-control pairs matched by age (+/-3 years) and gender (mean age, 48+/-14 yrs; ratio of women to men, 18/4). MAIN OUTCOME MEASURES: Target parameters were peak oxygen uptake (peak VO2) to estimate aerobic exercise capacity and peak isometric torque for muscle strength. Creatine phosphokinase (CPK) was measured to assess elevation of muscle enzymes. RESULTS: The mean peak VO2 in patients with dermatomyositis/polymyositis was 15.3 mL/min/kg (SD = 5.8) and in the healthy controls 28.7 mL/min/kg (SD = 7.8). Cardiorespiratory capacity expressed as peak VO2 was thus significantly reduced at 53% (p = .0001) of the control value. Muscle strength expressed as peak isometric torque was significantly lower (p = .01) in patients (mean 148+/-73 Nm) when compared to the control group (mean 261+/-99 Nm). In myositis patients peak VO2 and peak isometric torque correlate well with each other (r = .7631; p = .0001), but not at all with serum CPK levels (r = .056; p = .869). CONCLUSION: Peak VO2 is significantly diminished in patients with dermatomyositis/polymyositis, compared with age- and sex-matched controls. Serum CPK did not significantly correlate with VO2. Aerobic exercise testing may be a useful assessment parameter in selected patients with dermatomyositis/ polymyositis.

Relationship between craniomandibular disorders and poor posture.

The purpose of this research was to show that a relationship between craniomandibular disorders (CMD) and postural abnormalities has been repeatedly postulated, but still remains unproven. This study was intended to test this hypothesis. Twenty-five CMD patients (mean age 28.2 years) were compared with 25 gender and age matched controls (mean age 28.3 years) in a controlled, investigator-blinded trial. Twelve postural and ten muscle function parameters were examined. Measurements were separated into three subgroups, consisting of those variables associated with the cervical region, the trunk in the frontal plane, and the trunk in the sagittal plane. Within these subgroups, there was significantly more dysfunction in the patients, compared to control subjects (Mann-Whitney U test p < 0.001, p < 0.05, p < 0.01). Postural and muscle function abnormalities appeared to be more common in the CMD group. Since there is evidence of the mutual influence of posture and the craniomandibular system, control of body posture in CMD patients is recommended, especially if they do not respond to splint therapy. Whether poor posture is the reason or the result of CMD cannot be distinguished by the data presented here.

[Evaluating rehabilitation progress by measuring thigh circumference]. / Beurteilung des Rehabilitationsfortschritts mittels Oberschenkelumfangmessung.

QUESTION: Thigh girth measurements have been widely used to quantify rehabilitation progress following knee surgery, but the correlation between thigh girth and other functional measures has not been investigated. This study intended to investigate whether such a correlation exists. METHODS: 15 women with bilateral osteoarthrosis of the knee participated in this study. Isokinetic knee extensor strength, thigh girth and body mass were measured immediately before, then at six weeks and six months following cementless total knee arthroplasty. RESULTS: The involved side showed clear pre-operative isokinetic knee extensor strength deficits, and slight reductions in thigh girth. Post-operatively, mean strength deficits were reduced, whereas differences in mean thigh girth became lager. Although thigh girth changes correlated well with body mass, they did not correlate with knee extensor strength. CONCLUSION: Changes in thigh girth are mainly due to changes in body mass. Thigh girth measurement is of no use for the quantification of the rehabilitation progress in total knee arthroplasty.

Reliability of surface electromyographic measurements.

OBJECTIVES: The aim of the study was to investigate short-term, intermediate-term and long-term reliability of surface electromyographic (EMG) measurements. METHODS: Eighteen healthy subjects performed 810 isometric knee extension tests. Reliability for maximum voluntary contraction (MVC) and 50% MVC was assessed with retest intervals of 3 min, 90 min and 6 weeks. Reliability for sustained contractions was assessed with retest intervals of 90 min and 6 weeks. EMG was recorded from the rectus femoris, vastus lateralis and vastus medialis muscles. The root mean square (RMS) and the median frequency (MF) parameters were extracted. At sustained contraction tasks, estimated linear regression values of both parameters were analyzed. Bland-Altman-plots, coefficient of repeatability, Pearson's coefficient of correlation and intra class correlation (ICC) procedures were applied to assess test-retest reliability. RESULTS: EMG recordings taken at short-term intervals were generally better reproducible than those of the longer-term intervals. Moreover, 50% MVC EMG recordings demonstrated better reproducibility than 100% MVC measurements, and EMG recorded from the rectus femoris were more constant than that from the vastus lateralis or vastus medialis. The MF parameter recorded from the rectus femoris was the only reliable parameter of EMG fatigue change. CONCLUSION: In our set up, EMG measurement is best suited for clinical applications if submaximal MVC measurements are performed and signal is taken from rectus femoris muscle.

Cross-cultural adaptation of the Roland-Morris questionnaire for German-speaking patients with low back pain.

STUDY DESIGN: Cross-cultural adaptation and cross-sectional psychometric testing. OBJECTIVES: To develop and validate a cross-cultural version of the Roland-Morris Questionnaire for use in German-speaking patients with low back pain. SUMMARY OF THE BACKGROUND DATA: Clinical research related to the management of back pain would be facilitated enormously if a small number of patient-oriented questionnaires became widely used. If the transposition of a questionnaire from its original cultural context is done by simple translation, it is unlikely to be successful because of language and cultural differences. Therefore, a simple direct translation of a questionnaire from one language to another does not permit its use in clinical trials. METHODS: The instrument was translated and back-translated, pretested, and reviewed by a committee. The German version of the Roland-Morris Questionnaire was tested in 125 patients with low back pain. The study was conducted at the spa resort at Senftenberg, Austria, which is visited by patients from all countries of German-speaking Europe. Reliability and concurrent construct validity were assessed with Pearson's correlation coefficient on the Roland-Morris Questionnaire scores compared with the scales of the Medical Outcome Study Short Form-36 questionnaire. RESULTS: Pearson's correlation coefficient for test-retest reliability of the German version was r = 0.82 (P = 0.0001), and Cronbach's alpha was 0.81. The concurrent validity was r = 0.81 (Roland-Morris Questionnaire/pain rating; P = 0.0001), r = 0.48 (Roland-Morris Questionnaire/forward bending; P = 0.0001), and r = -0.47 (Roland-Morris Questionnaire/lateral bending; P = 0.0001). Correlation between the functional scales of the Medical Outcome Study Short Form-36 questionnaire and the Roland-Morris Questionnaire sum scores ranged from r = -0.29 (emotional limitations; P = 0.0011) to r = -0.71 (physical limitations; P = 0.0001). CONCLUSION: Because the German version of the Roland-Morris Questionnaire seems to be reliable and valid for the assessment of the functional status in German-speaking patients with low back pain, the use of this translated instrument can be recommended in future clinical trials.

Ultrasound therapy for calcific tendinitis of the shoulder.

BACKGROUND AND METHODS: Although ultrasound therapy is used to treat calcific tendinitis of the shoulder, its efficacy has not been rigorously evaluated. We conducted a randomized, double-blind comparison of ultrasonography and sham insonation in patients with symptomatic calcific tendinitis verified by radiography. Patients were assigned to receive 24 15-minute sessions of either pulsed ultrasound (frequency, 0.89 MHz; intensity, 2.5 W per square centimeter; pulsed mode, 1:4) or an indistinguishable sham treatment to the area over the calcification. The first 15 treatments were given daily (five times per week), and the remainder were given three times a week for three weeks. Randomization was conducted according to shoulders rather than patients, so a patient with bilateral tendinitis might receive either or both therapies. RESULTS: We enrolled 63 consecutive patients (70 shoulders). Fifty-four patients (61 shoulders) completed the study. There were 32 shoulders in the ultrasound-treatment group and 29 in the sham-treatment group. After six weeks of treatment, calcium deposits had resolved in six shoulders (19 percent) in the ultrasound-treatment group and decreased by at least 50 percent in nine shoulders (28 percent), as compared with respective values of zero and three (10 percent) in the sham-treatment group (P=0.003). At the nine-month follow-up visit, calcium deposits had resolved in 13 shoulders (42 percent) in the ultrasound-treatment group and improved in 7 shoulders (23 percent), as compared with respective values of 2 (8 percent) and 3 (12 percent) in the sham-treatment group (P=0.002). At the end of treatment, patients who had received ultrasound treatment had greater decreases in pain and greater improvements in the quality of life than those who had received sham treatment; at nine months, the differences between the groups were no longer significant. CONCLUSIONS: In patients with symptomatic calcific tendinitis of the shoulder, ultrasound treatment helps resolve calcifications and is associated with short-term clinical improvement.

The role of the biarticular agonist and cocontracting antagonist pair in isometric muscle fatigue.

Isometric knee extensions until exhaustion at 30%, 50%, and 70% of maximum voluntary contraction were performed by 18 healthy subjects. During muscle fatigue, surface electromyographic activity was recorded from the knee-extensors vastus lateralis, vastus medialis, and rectus femoris, and the coactive antagonistic biceps femoris. The electromyographic parameter median frequency (MF) served as a measure of fatigue. Coefficients of regression of the MF fatigue changes were analyzed statistically. MF fatigue occurred within the coactive biceps femoris and was significantly more pronounced than in the quadriceps. When the MF fatigue shifts of the coactive biceps femoris were compared with each of the three investigated parts of the quadriceps separately, MF fatigue shifts were similar in shape for the biarticular coactive biceps femoris and the biarticular rectus femoris, but differed significantly between the biceps femoris and the two monoarticular muscles, vastus medialis and vastus lateralis. As both the biarticular agonist and coactive antagonist muscles fatigued at a higher rate than the two monoarticular muscles, it seems likely that this biarticular agonist/antagonist pair determines the time to the limit of endurance.