Normal trunk muscle strength and endurance in women and the effect of exercises and electrical stimulation. Part 1: Normal endurance and trunk muscle strength in 101 women

A planar neuromuscular controller to simulate compensation strategies in the sit-to-walk movement

Standing up from a chair is a key daily life activity that is sensitive to functional limitations as we age and associated with falls, frailty, and institutional living. Predictive neuromusculoskeletal models can potentially shed light on the interconnectivity and interdependency of age-related changes in neuromuscular capacity, reinforcement schemes, sensory integration, and adaptation strategies during stand-up. Most stand-up movements transfer directly into walking (sit-to-walk). The aim of this study was to develop and validate a neuromusculoskeletal model with reflex-based muscle control that enables simulation of the sit-to-walk movement under various conditions (seat height, foot placement). We developed a planar sit-to-walk musculoskeletal model (11 degrees-of-freedom, 20 muscles) and neuromuscular controller, consisting of a two-phase stand-up controller and a reflex-based gait controller. The stand-up controller contains generic neural pathways of delayed proprioceptive feedback from muscle length, force, velocity, and upper-body orientation (vestibular feedback) and includes both monosynaptic an antagonistic feedback pathways. The control parameters where optimized using a shooting-based optimization method, based on a high-level optimization criterium. Simulations were compared to recorded kinematics, ground reaction forces, and muscle activation. The simulated kinematics resemble the measured kinematics and muscle activations. The adaptation strategies that resulted from alterations in seat height, are comparable to those observed in adults. The simulation framework and model are publicly available and allow to study age-related compensation strategies, including reduced muscular capacity, reduced neural capacity, external perturbations, and altered movement objectives.

Isokinetic evaluation of the trunk flexors and extensors in women with and without scoliosis: A comparative study

BACKGROUND: Scoliosis affects mainly women and even if its diagnosis relies on clinical evaluation and radiographic assessment, muscular involvement is undeniable impacting possibly on strength and daily activities. OBJECTIVE: To assess the strength of sagitally operating trunk muscles in women with scoliosis (WwS) and apparently healthy women (AH) with a similar mean age. METHODS: The two groups consisted 114 WwS and 42 AH women. The concentric isokinetic evaluation related to the peak moment (PM) of the trunk flexors and extensors at 30 and 90∘/s. Division into subgroups was based on the location of the scoliosis and magnitude of the Cobb angle. RESULTS: The PM of both muscle groups was not correlated with the location of the scoliosis. However, these muscles manifested a highly significant weakness in WwS compared to the AH group, in both test velocities. In terms of the general severity of the weakness, the PM scores in WwS with Cobb angle > 30∘ were significantly lower compared to their healthy counterparts in both ‘muscle’ and ‘velocity’ whereas save the flexors at 90∘/s, there was no difference between the lesser compromised WwS (Cobb ⩽ 30∘) and AH women. The PM-based extension/flexion ratios in WwS were respectively 1.34 ± 0.28 and 1.23 ± 0.27 at 30∘/s and 90∘/s, with no significant difference between subgroups, nor with control values. CONCLUSION: In view of the results, trunk muscles strength should definitely be taken into account when planning therapeutic options for WwS.

Reference values for muscle strength: a systematic review with a descriptive meta-analysis

BACKGROUND

Muscle strength is an important component of health.

OBJECTIVE

To describe and evaluate the studies which have established the reference values for muscle strength on healthy individuals and to synthesize these values with a descriptive meta-analysis approach.

METHODS

A systematic review was performed in MEDLINE, LILACS, and SciELO databases. Studies that investigated the reference values for muscle strength of two or more appendicular/axial muscle groups of health individuals were included. Methodological quality, including risk of bias was assessed by the QUADAS-2. Data extracted included: country of the study, sample size, population characteristics, equipment/method used, and muscle groups evaluated.

RESULTS

Of the 414 studies identified, 46 were included. Most of the studies had adequate methodological quality. Included studies evaluated: appendicular (80.4%) and axial (36.9%) muscles; adults (78.3%), elderly (58.7%), adolescents (43.5%), children (23.9%); isometric (91.3%) and isokinetic (17.4%) strength. Six studies (13%) with similar procedures were synthesized with meta-analysis. Generally, the coefficient of variation values that resulted from the meta-analysis ranged from 20.1% to 30% and were similar to those reported by the original studies. The meta-analysis synthesized the reference values of isometric strength of 14 muscle groups of the dominant/non-dominant sides of the upper/lower limbs of adults/elderly from developed countries, using dynamometers/myometer.

CONCLUSIONS

Most of the included studies had adequate methodological quality. The meta-analysis provided reference values for the isometric strength of 14 appendicular muscle groups of the dominant/non-dominant sides, measured with dynamometers/myometers, of men/women, of adults/elderly. These data may be used to interpret the results of the evaluations and establish appropriate treatment goals.

Subperiosteal transmission of intra-articular pressure between articulated and stationary joints

Hydrostatic pressures can be transmitted between synovial capsules. In each of ten rabbits, we simultaneously measured pressure in two joints, one of which was passively ranged, and the other of which was kept stationary. The intra-articular pressure inside the stationary joint changed every time its companion joint was ranged. But the pressure in the stationary joint did not change when the periosteum was transected above the ranged joint. This phenomenon was observed in all four animals that served as their own controls. The study suggests that the intra-articular pressure was transmitted through the space between the periosteum and the bone surface. Alternative explanations, like measurements of venous blood pressure, did not show correlation with hydrostatic pressure changes in the joints. The Floating Skeleton concept suggests a biomechanical rationale for this newly observed phenomenon: that there exists a subperiosteal hydrostatic connection of synovial joints, and that this "net" distributes excess pressures among joints through the periosteal sheath to sustain the integrity of the joint contacting surfaces over a lifetime.

Spinal mobility and trunk muscle strength in elite hockey players

Elite hockey players of both sexes from the Australian Institute of Sport were assessed for lumbar spine mobility, trunk flexion and back extensor muscle strength, hamstring flexibility and postural characteristics over a two year period. All the athletes were more mobile in rotation than the 'normal' West Australian population, and demonstrated flexible hamstrings and powerful back extensor muscles; trunk flexion was less strong initially, but improved after intervention in the form of a specific exercise programme, over the measurement period. A questionnaire disclosed that low back pain is a common complaint of hockey players, but rarely required intensive physical and medical treatment. The term 'hockey player's back' has been coined in recognition of the long flat thoracolumbar spine frequently noted in these subjects.

A NORMATIVE DATABASE OF ISOKINETIC UPPER-EXTREMITY JOINT STRENGTHS: TOWARDS THE EVALUATION OF DYNAMIC HUMAN PERFORMANCE

The objective of this study was to provide a normative database of dynamic upper-extremity (shoulder and elbow) joint strengths to fill the current void in literature for multidimensional strength capacity profiles. The isokinetic strength of the elbow and shoulder joints was tested for twenty normal males and females. The independent variables consisted of joint angular position, joint angular velocity, direction of exertion, and gender. The measured joint strength (torque, Nm) was the only defined dependent variable. The majority of existing joint strength prediction models and normative databases are static (isometric) in nature. The few available dynamic models are reported in the form of torque as a function of joint angle. Since joint strength is a function of both the joint angular position and angular velocity, descriptive models should take this interaction into consideration. The dynamic joint strengths of the subjects were studied using the KIN_COM 125E Plus. A second-order multiple regression analysis was used to model the dynamic 3-D strength surface response of each joint in each direction of exertion. Analysis of variance (ANOVA) with repeated measures design was used to test for the effects of gender, angular position, angular velocity, and direction on the dynamic strength of each joint, joint strength was significantly influenced by dynamic parameters such as the angular velocity. The interaction between angular position and velocity was highly significant. 3-D strength surface representation may be used as a "performance capacity envelope" to comprehensively characterize an individual's dynamic joint strength performance.

Effects of back posture education on elementary schoolchildren's back function

The possible effects of back education on children's back function were never evaluated. Therefore, main aim of the present study was to evaluate the effects of back education in elementary schoolchildren on back function parameters. Since the reliability of back function measurement in children is poorly defined, another objective was to test the selected instruments for reliability in 8-11-year olds. The multi-factorial intervention lasting two school-years consisted of a back education program and the stimulation of postural dynamism in the class. Trunk muscle endurance, leg muscle capacity and spinal curvature were evaluated in a pre-post design including 41 children who received the back education program (mean age at post-test: 11.2 +/- 0.9 years) and 28 controls (mean age at post-test: 11.4 +/- 0.6 years). Besides, test-retest reliability with a 1-week interval was investigated in a separate sample. Therefore, 47 children (mean age: 10.1 +/- 0.5 years) were tested for reliability of trunk muscle endurance and 40 children (mean age: 10.2 +/- 0.7 years) for the assessment of spinal curvatures. Reliability of endurance testing was very good to good for the trunk flexors (ICC = 0.82) and trunk extensors (ICC = 0.63). The assessment of the thoracic (ICC = 0.69) and the lumbar curvature (ICC = 0.52) in seating position showed good to acceptable reliability. Low ICCs were found for the assessment of the thoracic (ICC = 0.39) and the lumbar curvature (ICC = 0.37) in stance. The effects of 2 year back education showed an increase in trunk flexor endurance in the intervention group compared to a decrease in the controls and a trend towards significance for a higher increase in trunk extensor endurance in the intervention group. For leg muscle capacity and spinal curvature no intervention effects were found. The small samples recommend cautious interpretation of intervention effects. However, the present study's findings favor the implementation of back education with focus on postural dynamism in the class as an integral part of the elementary school curriculum in the scope of optimizing spinal loading through the school environment.

Association of low back pain, impairment, disability & work limitations in nurses

INTRODUCTION

Health care professionals use measures of pain and impairment to identify potential disability and subsequently to predict workers' ability to do their work. However, there is little evidence that measures used are associated with ability to do one's job.

METHODS

A cross-sectional study was conducted. Nurses (n = 100) were classified into either off/modified work (due to LBP) or regular work groups. Trunk ROM, trunk muscular endurance, pain and disability were measured relative to the outcomes work status and Work Limitations Questionnaire (WLQ) score.

RESULTS

Regression analyses which included Roland Morris Questionnaire (RMQ, disability) and Sørenson (back extensor endurance) in the final models correctly classified the work status of 87% of the participants and accounted for 60% of variance in the WLQ score.

CONCLUSIONS

Use of the RMQ and Sørenson test as diagnostic and prognostic tools should be considered in assisting return to work and treatment decision-making in female nurses with LBP.

The efficacy of a treatment program focusing on specific stabilizing exercises for pelvic girdle pain after pregnancy: a randomized controlled trial

STUDY DESIGN

A randomized controlled trial with stratified block design.

OBJECTIVES

To evaluate a treatment program focusing on whether specific stabilizing exercises for patients with pelvic girdle pain after pregnancy reduce pain, improve functional status, and improve quality of life. SUMMARY OF BACKGROUND DATA. : The evidence of effectiveness of treatment for pelvic girdle pain is weak. Recent research has focused on the importance of activation of muscles for motor control and stability of the lumbopelvic region. To the authors' knowledge, the efficacy of applying these principles for pelvic girdle pain has not previously been evaluated in a randomized controlled trial.

METHODS

Eighty-one women with pelvic girdle pain were assigned randomly to two treatment groups for 20 weeks. One group received physical therapy with a focus on specific stabilizing exercises. The other group received individualized physical therapy without specific stabilizing exercises. Assessments were administered by a blinded assessor, at baseline, after intervention and 1 year post partum. Main outcome measures were pain, functional status and quality of life.

RESULTS

There were no dropouts. After intervention and at 1 year post partum, the specific stabilizing exercise group showed statistically and clinically significant lower pain intensity, lower disability, and higher quality of life compared with the control group. Group difference in median values for evening pain after treatment was 30 mm on the Visual Analog Scale. Disability was reduced by more than 50% for the exercise group; changes were negligible in the control group. Significant differences were also observed for physical tests, in favor of the specific exercise group.

CONCLUSION

An individualized treatment approach with specific stabilizing exercises appears to be more effective than physical therapy without specific stabilizing exercises for women with pelvic girdle pain after pregnancy.

Intra- and inter-tester reliability and reference values for isometric neck strength

BACKGROUND AND PURPOSE

Age- and sex-specific reference values for neck strength based on reliable measurements in the upright position are lacking. The aim of the present study was to determine intra- and inter-tester reliability and age- and sex-specific reference values for isometric neck strength in extension, flexion and lateral flexion in sitting position measured with the David Back Clinic 140 (DBC 140) equipment.

METHOD

The reliability of the DBC 140 equipment was investigated in 30 healthy volunteers and reference values were obtained from 101 healthy men and women.

RESULTS

The reliability study showed that neck strength measured with the DBC 140 equipment has almost perfect intra- and inter-tester reliability (ICC values between 0.85 and 0.97). The mean value of the first in a series of three measurements was the highest for all three test leaders and for almost all directions. Results from the reference value study showed that gender is a much more important determinant of neck strength than age, body weight or body mass index (BMI). Neck strength in women was, on average, 55% of that in men, and when adjusted for body weight or BMI, the percentages were 70% and 59%, respectively. In all directions observed, neck strength decreased by approximately 20% from age 25 to 64 years.

CONCLUSIONS

Measurements of neck strength taken in upright position with the DBC 140 equipment have almost perfect intra- and inter-tester reliability and justify the use of this test procedure. The use of the first measurement in a test series can be recommended for use in clinical practice since it was shown to be the maximal test value and thus, had a very low intra-tester difference. The use of reference values for neck strength when evaluating patients with neck disorders needs to take gender into account.

Isometric back extension endurance tests: a review of the literature

OBJECTIVE

To review the literature that describes and evaluates the use of isometric back extension endurance tests.

DATA COLLECTION

Relevant articles in English were retrieved through a search of MEDLINE and the Index to Chiropractic Literature. Key search terms were back muscle endurance, isometric back endurance, trunk extensors, back muscle performance, and Sorensen test.

DATA SYNTHESIS

The principal criterion for inclusion was as follows: any study that discussed or tested an isometric type of back endurance extension test. Studies that were excluded did not use an isometric testing protocol. Thirty-seven of the initial studies are included in this review.

RESULTS

Six different types of isometric back extension endurance testing methods were found. Three of these procedures require special testing devices. Much of the research on this topic has centered on a procedure known as the Sorensen test. Normative databases have been established for the Sorensen test and 2 other test types. Validity and reliability have been assessed for some of the procedures.

CONCLUSIONS

The influence of motivation and effort exerted by the subject are limiting factors in all of the tests reviewed. These psychologic factors warrant further research. On the basis of the literature reviewed, we determined that the Sorensen is probably the most clinically useful of these tests; it is easy to perform, requires no special equipment, and enjoys the most support from the literature.

Intramuscular pressure in the erector spinae and intra-abdominal pressure related to posture and load

STUDY DESIGN

Intramuscular pressures in both Erectors Spinae and intra-abdominal pressures were measured during different holding tasks.

OBJECTIVES

To investigate the potential for using intramuscular pressure measurements in both Erectors Spinae to better quantitate the role of muscles during different lifting tasks in vivo.

SUMMARY OF BACKGROUND DATA

Intramuscular pressure and intra-abdominal pressure were measured previously under isometric and dynamic conditions. However, no previous study systematically has addressed the relation between intramuscular and intra-abdominal pressures and different loads, tasks, and postures.

METHODS

Intramuscular and intra-abdominal were measured simultaneously with microtip pressure transducers in 10 healthy volunteers performing 24 different static holding tasks. Tasks included different weights (10 kg and 20 kg), postures (squat or back lift), and positions of the weight.

RESULTS

Intramuscular pressures were dependent on posture. Kyphotic back posture produced intramuscular pressures of 120-130 mm Hg, compared with the 10-25 mm Hg produced when volunteers were in the erect position (P < 0.001). Holding a 10-kg weight at the thighs close to the body produced significantly (P < 0.001) lower intramuscular pressures (25-32 mm Hg) than that produced by holding it 25 cm in front of the body (47-56 mm Hg). In all tasks, intramuscular pressures were significantly higher with the 20-kg weight than with the 10-kg weight (P < 0.001). Highest values (> 300 mm Hg) were measured when the 20-kg weight was held in the kyphotic posture above the floor and 25 cm away from the body.

CONCLUSIONS

Intramuscular pressure measurements in the erector spinae seem to be a valuable tool for quantitating the role of back muscles during different lifting tasks.

Differentiation of submaximal from maximal trunk extension effort: an isokinetic study using a new testing protocol

STUDY DESIGN

An evaluation of the relations between concentric and eccentric contractions of the trunk extensors and extension effort performed at maximal and submaximal levels.

OBJECTIVE

To define quantitative parameter(s) derivable from isokinetic dynamometry that may differentiate submaximal from maximal trunk extension moment.

SUMMARY OF BACKGROUND DATA

Using various consistency-related parameters, researchers in previous studies have not been able confirm the potential of isokinetic dynamometry for identifying submaximal effort during trunk extension.

METHODS

Twenty healthy subjects, 8 women and 12 men without low back pain history, aged 21 to 30 years, took part in this study. Testing consisted of three experimental conditions using four intermittent concentric and eccentric contractions at 20 degrees and 60 degrees/second. The first condition, in which subjects were asked to exert maximal concentric and eccentric effort, served as the baseline. In the second condition, subjects were asked to exert 50% of the force measured in the first condition. In the third condition, subjects repeated the second condition but were asked to exert the best reproducible level of force.

RESULTS

The highest differentiating power among the experimental conditions was attributed to the intervelocity difference between the concentric and eccentric contractions (P < 0.0001).

CONCLUSIONS

This protocol effectively differentiates submaximal from maximal trunk extension effort in normal subjects.

Trunk rotatory muscle performance in post-stroke hemiplegic patients

This study was undertaken to determine whether the direction of trunk rotation would have any effect on trunk muscle performance of post-stroke hemiplegic patients. The design consisted of a nonrandomized control trial in a setting of secondary care (rehabilitation unit at hospital facility). The subjects included 65 hemiplegic patients (50 males) and age-matched 80 healthy controls (38 females). Isokinetic trunk rotatory muscle performance at angular velocities of 60, 120, and 150 degrees per second was measured by using an isokinetic dynamometer (Cybex Torso Rotation Unit). There were no significant differences in the peak torque and best work between the right and left directions of the trunk rotation in the hemiplegic patients or in healthy controls, regardless of the gender of the subjects (paired t test, P > 0.05). The muscle performance of the hemiplegic patients was significantly lower than that of the controls for both genders (t test, P < 0.05). In the hemiplegic patients, the direction of trunk rotation does not affect the trunk rotatory muscle performance, although the performance itself was slightly decreased.

Reliability of electromyographic power spectral analysis of back muscle endurance in healthy subjects

OBJECTIVE AND DESIGN

To investigate the reliability (within-day and between-days) of measurements of electromyographic (EMG) power spectral values in measurement of the fatigue rate of the back muscles.

METHODS

Twelve healthy male subjects were tested in the unsupported trunk holding position for 60 seconds. Two trials were performed on each of two separate sessions 3 days apart. Surface recording electrodes were placed over the iliocostalis lumborum and multifidus and a branched electrode technique was used to decrease cross-talk.

OUTCOME MEASURES

Median frequency (MF) was extracted from the EMG signals by fast Fourier transform. Initial MF and the MF slope over time were computed from linear regression analysis. The reliability of the initial MF and the MF slope of the iliocostalis lumborum and multifidus was examined by Pearson's product moment correlation coefficients (Pearson's r), paired t tests, and a one-way analysis of variance (ANOVA) from which intrasubject coefficients of variation (CVintra) and intraclass correlation coefficients (ICC) were derived.

RESULTS

For the initial MF, within-day and between-days reliability of the iliocostalis lumborum and multifidus were good (Pearson's r = .79-.94 nonsignificant paired t test, CVintra = 6.5% to 8.5%, ICC = .79-.93). The MF slope showed moderate variability for the iliocostalis lumborum (Pearson's r = .39-.55, nonsignificant paired t test, CVintra = 33.0% to 48.7%, ICC = .37-.56) while better reliability was found for the multifidus (Pearson's r = .77-.87, nonsignificant paired t test, CVintra = 25.8% to 27.5%, ICC = .78-.82).

CONCLUSION

The present study indicated that the trunk holding test with the use of EMG power spectral analysis can be a reliable method to measure the fatigue rate of the back muscles if adequate measures are employed to minimize cross-talk. The better reliability of monitoring the fatigue rate of the multifidus may lead to its future use as a clinical measure.

Lumbar trunk muscle endurance testing: an inexpensive alternative to a machine for evaluation

OBJECTIVES

The goals of this study were to verify the reliability and safety of new methods for evaluating trunk muscle endurance, and to compare the differences between healthy subjects and patients with chronic low-back pain.

DESIGN

Randomized and controlled study.

SETTING

A referral center and institutional practice, and outpatient care.

SUBJECTS

Ninety healthy subjects (37 men and 53 women average age 46.2 years) and 100 patients with CLBP (40 men and 60 women; average age 45.3 years) participated in this study.

MAIN OUTCOME MEASURES

During trunk flexor and extensor endurance tests, the subjects were asked to maintain the original positions for as long as possible. The performance time (seconds) for which subject could maintain the position was compared between two groups. Test-retest correlation (r) was also analyzed. The degree of lumbar lordosis was compared in conventional and new methods.

RESULTS

All test-retest correlations were significantly high in both groups (p < .01). The performance time was much longer in the healthy subjects than in the patients with CLBP during any procedures (p < .01). Lumbar lordosis was significantly less in our method than in the Kraus-Weber test (p < .01).

CONCLUSIONS

This study demonstrated that our methods for measuring trunk flexor and extensor endurance had high reliability, reproducibility, and safety, and were easy to perform, with no need for special equipment. This study also showed that trunk muscles in patients with CLBP were more easily fatigued, compared with those in healthy subjects.

Correlations of isokinetic and psychophysical back lift and static back extensor endurance tests in men

Isokinetic lift, psychophysical lift, and static back endurance tests are among the most widely used measurements of muscle function for determining risk for, and recovery from, back problems. After determining test repeatability we examined the degree of association between these test measures in 100 men selected to represent a variety of occupations and lifestyles. Isokinetic lifting had low correlations with test results for psychophysical lifting (r = 0.28) and static back endurance (r = 0.24). Static back endurance and psychophysical lift test results were not at all correlated (r = 0.03). RELEVANCE--:Muscle function measurements for back problems are sometimes arbitrarily selected due to health practioners' beliefs and preferences or practical reasons such as the availability of equipment. Yet little is known about the associations of these tests with one another or with anthropometric factors. The data presented in this study document that isokinetic lift, psychophysical lift, and static back endurance tests appear to measure very different aspects of muscle function, and comparing studies using these different test methods should be approached with these low inter-test correlations in mind.

Paradoxical variation of strength determinants with different rotation axes in trunk flexion and extension strength tests

The aim of this study was to illustrate the influence of different levels of the fulcrum (the axis of sagittal rotation) on measured trunk flexion and extension strength and compare force and torque as a unit of measure. The isometric trunk strength was measured in 16 healthy female subjects. The dynamometer was kept at the shoulder level and the moment arm was lengthened step by step by moving the fulcrum caudally from the level of the posterior superior iliac spine to the level of the gluteal fold. The moment of force (torque) increased from 117.0 to 208.5 N.m in flexion and from 182.2 to 292.5 N.m in extension, P < 0.0001. An attempt to quantify this change was made. Paradoxically, the measured force remained at a constant level (in flexion) or slightly decreased (in extension). We concluded that torque as a measure of trunk flexion and extension strength is highly dependent on the level of the rotation axis and force appears to be less sensitive for variations with the height of the fulcrum. We would suggest that the observed increase in torque is physiological and reflects to what extent hip flexor or extensor muscles are recruited. The force, on the other hand, may better characterize a person's capability to perform functional tasks. Force and torque should strictly be distinguished from one another.

Influence of repeated measurements on isokinetic lifting strength

The aim of the study was to evaluate the effect of repeated measurements on isokinetic lifting strength in a smaple of patients with low back pain. The measures were performed in series of five consecutive lifts on two occasions 1-13 days apart, and the patients continued their normal living during this period. A group of healthy subjects was used as a control. The hypothesis was that a mere repetition of the lifting procedure would increase the performance, and that the increase would be bigger in the patient group that in the non-patient group. In addition, grip strength was measured on both occasions. It was supposed that grip strength would not change from trial 1 to trial 2. The results showed an increase in lifting strength from first to second trial in the patient group by an average of 28%, and in the control group by an average of 16%. Grip strength did not increase in either group. The last of five consecutive lifts was the best one in a majority of the cases in both trials. Neither five consecutive lifts nor measurements on two different occassions seem enough to define a reliable baseline for maximal lifting capacity. Other factors than an increase in muscle strength influence the performance, one being a repetition of the lifting procedure. This must be accounted for when defining a baseline for isokinetic lifting capacity.

Isokinetic trunk strength and lumbosacral range of motion in elite female field hockey players reporting low back pain

This study was funded, in part, by a Small Faculties Grant from the University of Alberta. Physical therapists have reported an increased incidence of low back pain (LBP) in female field hockey (FH) players, commonly accompanied by decreased trunk range of motion (ROM) and strength. The purpose of this study was to compare lumbosacral sagittal ROM and isokinetic trunk strength in three groups of women: 1) FH athletes with a history of chronic LBP, 2) pain-free FH athletes, and 3) an age-matched, healthy nonathletic control group. Photographs (35 mm) of subjects wearing spinal motion markers were used to determine the limits of lumbosacral saggital ROM in standing. Eccentric and concentric isokinetic trunk flexion and extension torques were measured in sitting through 60 degrees of trunk movement using a Kin-Com dynamometer set at 60 degrees /sec. The ANOVA showed that the pain group had 12 degrees and 18 degrees less extension (p < .01), as well as 18 degrees and 24 degrees less total ROM (p < .001) than the pain-free and control groups, respectively. Only peak (p < .001) and average (p < .03) eccentric extension torques were weaker in the pain group than in the nonathletic control group. These results suggest that physical therapists should perform preseason screening of trunk strength and lumbosacral ROM. In-season trunk extension stretching and strengthening is needed in the training regimes of these athletes. J Orthop Sports Phys Ther 1992;16(3):129-135.

Electromyography of lumbar erector spinae muscles--influence of posture, interelectrode distance, strength, and fatigue

The aims of the study were to obtain information (1) on surface electromyograms (SEMG) from the lumbar erector spinae muscles at different interelectrode distances and postures during short isometric contractions with constant force, (2) on the relationships between SEMG and extension force at different postures, and (3) on changes in SEMG during fatiguing isometric contractions at different postures and strengths. Six male subjects developed target forces in prone postures without gravity confounding the measurement of the extension torque. The angles between the constantly horizontal upper trunk and thighs were 90 degrees (P1), 135 degrees (P2), 170 degrees (P3), and 190 degrees (P4). Standard deviations of the distribution of SEMG amplitudes (RMS values), autoregressive (AR) time series models of the 15th order and spectral densities, including mean power frequency (MPF), were computed. Smaller interelectrode distances accompanied smaller RMS values and higher MPF. At a constant extension torque of about 110 Nm, RMS values and MPF increased from P1 to P4. Changes of interelectrode distance were of relatively minor importance, compared with the variation in the posture. With increasing torque, the increase in RMS values was steeper at P3 than at P2. The AR structure and MPF did not exhibit distinct effects of force. During sustained contractions at P2 and P3, only the highest force (mean = 140 Nm) at P3 caused a significant decrease of the MPF at the very beginning of the contraction. Endurance at P2 was greater than at P3. Higher forces and/or shorter muscles (P3) induced more pronounced and earlier relative decreases of the MPF and residual variance of AR models. Up to the "failure point", RMS values increased slightly, but without significant differences.

Isokinetic lifting simulation: a normative data study

This article describes a system for data collection using an isokinetic lifting task simulation device and reports normative data findings based on a standardized lifting posture. The test population included 2688 normal subjects (1236 females, 1452 males; ages 10-79 years) from five different occupational categories who were tested on a Liftask device using a flexed knees-flexed back lifting posture. Testing consisted of four maximal lifting repetitions preceded by three gradient submaximal repetitions plus one maximal effort at the speeds of 6, 12, 18, 24, 30, and 36 inches/sec. Data on peak force, peak force as percent of body weight, height of peak force, average force, average force as percent of body weight, average power, and total work were categorized by sex and age decade for reporting as normative experimental results. In general, overall performance decreased in an inverse proportion to test speed while height of peak force and average power increased in direct proportion to speed. Also, subject performance increased from the 10-19 decade to the 20-29 decade before decreasing with age through the 70-79 decade. The results may be useful for clinical reference purposes as normative data for the purposes of performance comparisons during isokinetic lifting with a flexed knee-flexed back posture.J Orthop Sports Phys Ther 1988;10(5):156-166.