Human plantarflexor stiffness to multiple single-stretch trials.

The purpose of this investigation was to determine the influence of different stretch velocities, different rates of pre-stretch force development, and different pre-stretch muscle lengths on the intrinsic stiffness exhibited by the quasi-statically contracting active human plantarflexors during multiple single-stretch trials at 20-60% of maximum isometric contraction. Subjects were positioned prone, with the knee flexed 1.57 rad(90 degrees), shank stabilized, and foot secured in a hard plastic orthotic. Slowly increasing isometric plantarflexion force was produced until the plantarflexors were stretched by a rapid 0.2 rad (12 degrees) dorsiflexion movement. Plantarflexion forces and ankle positions were determined during these stretches as well as during resting stretches when the muscle was inactive. Resting forces were subtracted from the active trials, forces converted to torques, and stiffnesses determined for the first 62 ms of the stretch. The slope of the stiffness vs pre-stretch torque relationship averaged 4.30 +/- 0.34 Nm rad-1 Nm-1. Little difference was found between stiffness determined through the single-stretch method and the results of previous studies employing different mechanical inputs. Differences in stiffnesses with different stretching velocities were caused by computational artifact rather than by differences in intrinsic muscular reaction. Faster rates of pre-stretch force increase prior to the stretch resulted in slightly lower stiffnesses. Different pre-stretch muscle lengths apparently did not result in different stiffnesses. The shape of the torque vs displacement curve was remarkably insensitive to the planned manipulations of the testing conditions, responding in a stereotypical manner.

Analysis of strength tests and resistive exercises commonly used for low-back disorders.

Using a modeling approach the conventional sit-up, the double straight-leg lowering, and prone trunk extension, the authors have shown these to have limitations as tests of maximum trunk flexion and extension strength and as modes of resistive exercise. These maneuvers are poor discriminators of trunk muscle strength, and they lack the range of resistance necessary to cover the spectrum of human trunk muscle strength capability. Use of manually handled weights can improve the above clinical tests and resistive exercise methods. As a result of selective positioning of the weights, variable resistance above and below that provided by the body segments alone can be achieved. The partial sit-up may be appropriate only for patients with significant trunk flexion weakness, and the straight head-trunk sit-up may be useful as a more strenuous test and resistive exercise. Rationale and derivations of the rigid-body equilibrium equations, as well as some of the limitations and assumptions associated with the modeling approach, are presented.

Exploration of mechanical and electromyographic responses of trunk muscles to high-intensity resistive exercise.

The purposes of this study were to determine the effects of high intensity exercise on fatigue of the trunk muscles within a test session, and on multiple kinetic and electromyographic (EMG) variables over a 6-week training period. Fourty-five normal men and women (20-40 years of age) completed the study. The KIN/COM trunk testing unit (Chattecx Corporation, Chattanooga, Tennessee) was used for both testing and training. The results of the study follow: 1) The KIN/COM trunk testing system was very accurate, and the method used was highly reproducible for the kinetic variables. Reproducibility for the endurance variables was mixed, and isolated EMG variables were poor. 2) Kinetic and EMG decrements associated with fatigue did occur in the trunk muscles with ten continuous cycles of maximal concentric and eccentric contractions. 3) Trunk muscle strength gains were highest for the same mode of exercise used in training (specificity), but significant strength gains also were seen in different modes of muscle contraction (transfer of training). For the trunk extensors, the eccentric form of exercise was superior. 4) The rate of isometric torque development and decay was increased by exercise in men. 5) Trunk muscle endurance was retained when gains in strength occurred. 6) The majority of variables reflecting strength and endurance were retained. The methods and results can serve as guidelines for the evaluation of trunk muscle function and resistive exercise in the clinic.

Sacroiliac kinematics for reciprocal straddle positions.

STUDY DESIGN: A descriptive and correlation approach was used to assess joint motion. OBJECTIVES: Magnitudes and directions of sacroiliac motion were examined from three different upright postural conditions. SUMMARY OF BACKGROUND DATA: Evidence and clinical views suggest that sacroiliac motion available in the normal case is extremely small to nonexistent. METHODS: Systems for standardizing the three postures and the Metrecom skeletal analysis system (Metrecom, Faro Technologies, Inc., Lake Mary, FL) for acquiring coordinate data for selected skeletal landmarks. RESULTS: The complete sacroiliac oblique-sagittal motion that occurred between the right forward and left forward stride positions was 9 degrees (SD 6.5). The composite oblique-transverse motion was 5 degrees (SD 3.9). The motions in each plane were significantly different from zero. A joint mobility relationship existed between the hip and sacroiliac joints. CONCLUSION: The results demonstrate that substantial angular motion is possible at the sacroiliac joints.

The effect of high-intensity trunk exercise on bone mineral density of postmenopausal women.

The purpose of this study was to determine the effect of a 1-year trunk resistive exercise program on bone mineral density at the lumbar spine and hip in postmenopausal women. Forty-nine subjects were divided into exercise and control groups. Dual photon absorptiometry was used to measure bone mineral density and the Muscle Examination and Exercise Dosimeter 3000 system was used to assess trunk muscle strength. Resistive exercise target levels for the exercise group were based on the results of the trunk muscle strength tests. The exercise group performed 3 sets of 10 repetitions for each of the sit-up, prone trunk extension, and double leg flexion exercises. The subjects were seen once per month and performed the exercises a minimum of three times per week. The bone mineral density and strength tests were done at baseline, at 6 months and at 12 months. The results of the study showed that 1) the dual photon absorptiometry method and the Muscle Examination and Exercise Dosimeter 3000 system were highly reliable in measuring bone mineral density and trunk muscle strength, respectively; and 2) no significant differences were found between the exercise and control groups at lumbar vertebrae L2, L3, L4, L2-L4, and the femoral neck, Ward's triangle, and trochanteric region of the proximal femur at baseline, 6-month, and 12-month evaluation sessions.

Comparison of clinical and objective methods of assessing trunk muscle strength--an experimental approach.

An objective method was used to evaluate the validity of the sit-up, prone trunk extension, and double leg lowering clinical tests. Normal men and women and patients with a history of backache served as subjects. The vast majority of the subjects were able to perform the Grade 1 level, which was the highest resistance imposed by the sit-up and prone extension tests. The double leg lower was superior to the other two clinical tests but was able to identify only broad differences in strength capability. In the main, the subjective clinical tests were poor discriminators and seemed to lack the range of resistance necessary to be definitively useful as methods of assessing trunk muscle strength and may not provide appropriate resistance for improving trunk muscle strength in most patients.

Sacroiliac motion for extreme hip positions. A fresh cadaver study.

STUDY DESIGN: This study placed fresh cadavers in different hip positions and obtained sacroiliac kinematics. The magnitudes and directions of angular and linear sacroiliac motion are reported. OBJECTIVES: To determine the three-dimensional motion at the left and right sacroiliac joints and to explore the mechanical structure of the sacroiliac joint. SUMMARY OF BACKGROUND DATA: Previous in vivo and in vitro studies have reported various amounts of motion at the sacroiliac joints, ranging from no motion to 18 degrees. The results of previous studies have typically not been reported as data in classic engineering terms, and three-dimensional analyses are sparse. Importantly, previous studies have not used external hip positions to elucidate the full range of sacroiliac motion. METHODS: Radiopaque markers were placed in the sacrum and each innominate bone before standardized performance of computed tomography scans at 3-mm intervals, with the fresh cadaver stabilized in the side-lying position on a specially constructed pallet. Computed tomography images were stored on magnetic tape, from which coordinates for centroids of the markers were obtained and subsequent mechanical analyses performed. The intersubchondral lines on the images were traced and reconstructed using computer technology to obtain the thickness of the intersubchondral joint space and the general configuration of the sacroiliac joints. RESULTS: The methods used in this study were validated. The largest amount of sacroiliac motion occurred in the sagittal plane (7 degrees on left and 8 degrees on the right, with a range of 3 degrees to 17 degrees). Definite trends in the direction of angular sacroiliac motion occurred with respect to both bilateral and reciprocal hip joint positions. The translation or linear motion of the posterior superior iliac spines with respect to the sacrum ranged from 4 to 8 mm. This motion tended to occur in all directions, with no detectable trends. The average intersubchondral thickness of the sacroiliac joint was 1.2 mm and the shape of the joint resembled that of an airplane propeller. CONCLUSIONS: Even though the subjects in this study were elderly, considerable angular and linear motion was in evidence. As such, it appears that extreme hip positions are necessary to elucidate full range of motion at the sacroiliac joint. The magnitude and direction of demonstrated sacroiliac motion appears to be sufficient to complement hip joint motion and influence motion at the lumbosacral junction and, thus, low back pain in both the direct and indirect sense.

Effect of cane on variables of gait for patients with hip disorders.

The purposes of this study were to determine the effect of a cane, used in the hand contralateral to the involved hip, on patients' floor reaction forces and on selected time and distance measurements of gait. An instrumented cane, force plate, dynograph recorder and footswitch were among the equipment items used. When the patients walked with a cane the stride length and swing times were increased, while the cadence and the vertical component of the floor reaction force were decreased. The average peak axial loading on the can was 11.6 kg and the average anterior bending moment on the cane was 67.3 kgcm.

Factors contributing to the regulation and clinical assessment of muscular strength.

This paper reviews the physiological, anatomical, and biomechanical factors that contribute to the regulation of muscular strength and the factors to be considered in the clinical assessment of strength. In light of the procedural and mechanical aspects discussed, a comparison of various strength testing methods is made in order to assist the therapist in selecting the appropriate testing procedure to meet his objectives.

Quantitative gait evaluation in the clinic.

The purpose of this paper is to present a clinically feasible method to provide objective, quantitative information regarding the quality of a patient's gait. The technique used is simple and economical and requires minimal equipment. The four basic temporal and distance factors are 1) stride length, 2) step length, 3) cadence, and 4) velocity. The technique requires the following equipment: 1) grid pattern, 2) stop watch, 3) portable tape recorder, 4) tape measure, 5) marking pen, and 6) masking tape. Case examples are provided to demonstrate the use of the data obtained.

System of reporting and comparing influence of ambulatory aids on gait.

The purposes of this study were to 1) present a standardized approach for describing gait when assistive devices are used, 2) report reference data for unassisted and assisted gait patterns for normal adults, and 3) discuss clinical implications for selected variables of gait. Using an automated gait system, measurements for temporal and distance factors and accelerometry were obtained for 25 normal young adults. In addition to the formulation of a new system for describing gait patterns when assistive devices are used, the results of the study were that 1) subjects walked slower with ambulatory aids than without them, 2) assisted gaits with the same number of counts per cycle tended to have similar measurements, 3) reciprocal swing times and stance times were symmetrical for all types of gait studied, 4) double stance times and step times were asymmetrical for three types of assisted gait, and 5) vertical accelerations were disproportionately elevated for most assisted gaits.

Effect of pelvic tilt on standing posture.

Low back dysfunction is associated in many cases with lumbar lordosis, and tilting the pelvis posteriorly is often recommended for therapeutic purposes. The influence of pelvic tilt on the spinal curves has not been studied. The purpose of this study was to use an objective noninvasive method to determine the effect of the pelvic tilt on the spinal curves in the sagittal plane. Thirty-two healthy subjects and 15 patients with chronic low back dysfunction (CLBD) were studied. Patients with CLBD and healthy subjects were instructed in performing active anterior and posterior pelvic tilt maneuvers, first in the supine and then in the standing position. Comparisons between the Patient Group and the Healthy Group were made for several variables representing the severity of spinal curves, pelvic orientation, hip orientation, and knee orientation. A computerized system, the Iowa Anatomical Position System, was used to obtain coordinates of external body surface landmarks from which pelvic tilt measurements were determined. The results showed that the voluntary pelvic tilt did not alter the thoracic spinal curve. For both the Healthy Group and the Patient Group, the lumbar curve was altered by the pelvic tilt: anterior tilt increased the depth of the lumbar curve and posterior tilt decreased the depth of the lumbar curve. The amount of pelvic tilt was the same whether knees were extended or flexed approximately 10 degrees. Pelvic tilt also tended to influence the orientation of the head and other parts of the body.

Accelerographic, temporal, and distance gait factors in below-knee amputees.

Gait characteristics of 19 patients with a unilateral below-knee amputation were studied. The accelerographic and foot placement method used in this study allowed for simultaneous acquisition of data commonly obtained in the experimental laboratory (acceleration) and data easily gathered in the physical therapy clinic (temporal and distance factors). The following results may be of interest to the clinician: 1) measures of cadence, stride length, and velocity were highly related and the magnitude of these measures was below commonly accepted values for normal; 2) the below-knee amputees spent more time in stance phase on their uninvolved lower extremity than on their involved (prosthetic) extemity; 3) the step length from heel strike of the uninvolved lower extremity to heel strike of the involved (prosthetic) lower extremity was greater and accomplished in less time than the opposite step; and 4) smoothness of the gait pattern and any single temporal and distance factor exhibited low statistical relationships.

Relationship between trunk muscle torque and bone mineral content of the lumbar spine and hip in healthy postmenopausal women.

The purpose of the study was to determine the relationship between trunk muscle strength and bone mineral density (BMD). Fifty-six postmenopausal women, aged 38 to 73 years, were examined. The BMD of lumbar vertebrae L2-4, the femoral neck, the Ward's triangle, and the greater trochanter was measured with dual-photon absorptiometry. Isometric and isokinetic torque and work measurements obtained on a trunk testing unit were used to assess trunk flexor and extensor strength. Correlation analysis demonstrated a statistically significant relationship between most trunk torque and work measurements and BMD. The trunk extensors generally provided higher correlations with BMD than did the trunk flexors, and the isokinetic extension torque values demonstrated higher correlations than the isometric extension values in every case. Linear backward-regression models, based on the subjects' weight and trunk flexor and extensor torque and work measurements, demonstrated multiple-correlation coefficients of .67, .58, .43, and .65 in predicting the BMD of the L2-4 region, femoral neck, Ward's triangle, and greater trochanter region, respectively. Estrogen therapy status did not affect the linear regression models. These data suggest a positive relationship in postmenopausal women between flexor and extensor torque values and BMD at the lower lumbar spine and proximal femur.

Relationship of extremity muscle torque and bone mineral density in postmenopausal women.

The purpose of this study was to examine the correlations between the torque of four extremity muscle groups and the bone mineral density (BMD) of the lumbar spine and hip in postmenopausal women. Fifty-six postmenopausal women (means age = 55.4 years, s = 7.1; means height = 162.6 cm, s = 6.4; means weight = 65.9 kg, s = 9.3) served as subjects. Bone mineral density was measured from the L2-L4 vertebral bodies, greater trochanter, femoral neck, and Ward's triangle using dual-photon absorptiometry. Hip abduction, knee extension, hip flexion, and grip force were assessed using the Spark Muscle Examination and Exercise Dosimeter (MEED) 3000 system. The Pearson product-moment correlations between muscle torque and BMD ranged from .07 to .42. The significant (p less than .05) correlations between torque and BMD (r = .27-.42) occurred in functionally and anatomically related areas. Results of this study demonstrate a statistically significant relationship between torque and BMD in anatomically related areas in postmenopausal women. This relationship, however, is not sufficiently strong to allow for prediction of BMD from the four muscle groups tested in this study. The relationship does suggest that strength may be a factor in the determination of BMD. Maintenance of strength in those muscle groups with anatomical or functional relationships to the hip and lumbar spine may play a role in the prevention and cessation of the osteoporotic changes that occur.

The influence of isometric exercise and passive stretch on hip joint motion.

A method was designed to compare the effects of isometric contractions and passive stretch on modifying joint range of motion in 30 normal men. Subjects were randomly assigned into a control group, a passive stretch group, or an isometric contraction group. Each subject assumed a left sidelying position on the force table. Stabilization was applied to the pelvis and left lower extremity. The cuff, to which the force cable was attached, was applied to the right lower extremity. Force measurements produced by the isometric contractions or passive stretch procedures were stored on computer tape. The results of the mean differences in pelvifemoral angle measurements indicated that both treatment groups significantly increased their range of passive hip flexion with the knee extended when compared to the control group. Comparisons between the two treatment groups indicated that the isometric contraction and passive stretch procedures had significant and similar effects.

Sitting posture in a waiting-room environment.

Information on sitting posture in a leisure environment is lacking. The purpose of this study was to determine the prevalence of various sitting postures by observing adults in straight-backed chairs in the waiting areas of several airport terminals. A total of 374 subjects (231 men, 143 women) were studied. The majority of the subjects used the backrest (87%). Men more frequently sat in the slouched position than did women. Most of the group (87%) used a crossed-leg position; women predominantly used the knee-over-knee crossed-leg position while the men slightly favoured the ankle-over-knee crossed-leg position. No preference for laterality was found with respect to the crossed-leg sitting postures.

Spine configuration and range of motion in normals and scoliotics.

The purposes of this study were twofold: to observe the effects of various seated postures on normal and scoliotic spines, and to investigate thoracolumbar range of motion in both normal and scoliotic spines. Eleven adolescent females with mild adolescent idiopathic scoliosis involving the thoracolumbar spine, and 20 healthy female subjects participated in the study. The Iowa Anatomical Position System was used to analyse the lumbar spine curvature. The five upright postures examined were standing, side-bending left, side-bending right, trunk extension, and trunk flexion. The seated postures consisted of erect sitting, slouched sitting, and each leg crossed two different ways in both erect and slouched positions. All seated postures were found to lie well within the extreme passive ranges of motion established by side-bending left, side-bending right, extension, and flexion. The thoracolumbar ranges of motion for scoliotics and normals were similar. Seated postures decreased the lumbar lordosis exhibited in standing for both scoliotics and normals. In general, the variety of seated postures had similar effects in normals and scoliotics, and individual seated postures varied little from each other in their effects on the thoracolumbar spine. All seated postures increased the lateral curvature in scoliotics.

Serial assessment and treatment of a humeral fracture.

Clinical problems at the glenohumeral joint, whether chronic or induced by trauma, tend to manifest joint hypomobility with accompanying. muscle weakness. Fractures at the proximal humerus tend to occur more frequently in older patients, but in the presence of violent trauma this injury may occur in the younger patient as well.' The initial treatment often includes some form of immobilization followed by remobilization and muscle strengthening. There is a clinical need to document the sequence and form of physical therapy treatment and quantitatively reflect changes in joint motion and strength. A case study of a patient with a proximal humeral fracture is presented to (a) dezcribe the clinical findings and treatment associated with a shoulder injury, (b) describe and illustrate some methods of assessment and treatment, and (c) report results for joint motion and muscle strength. The hope of the author is that this paper might provide an example of physical therapy evaluation and treatment for such a case and demonstrate a model for expected results. Further, this paper might be used as a teaching model for therapists who are unexperienced with this type of patient.J Orthop Sports Phys Ther 1980;2(1):25-34.

Dynamic scapulohumeral rhythm: the effects of external resistance during elevation of the arm in the scapular plane.

The purpose of this study was to characterize the scapulohumeral rhythm in the normal shoulder during dynamic elevation of the arm in the scapular plane and to compare the scapulohumeral rhythm during three different states of loading: 1) arm completely unloaded and passively elevated, 2) light load consisting of active elevation against the weight of the limb, and 3) heavy loading against maximal resistance. Electromagnetic tracking was used to record three-dimensional scapular and humeral kinematics on 25 normal subjects. Cardan angles were calculated to assess the dynamic relationship of humeral elevation to scapular upward rotation. The results show that during dynamic humeral elevation the scapulohumeral rhythm changes depending on the phase of elevation and the external load on the arm. During passive range of motion, the scapulohumeral rhythm decreased from 7.9:1 to 2.1:1 as the arm was elevated. Light shoulder loads caused an increase of the scapulohumeral rhythm from 3.1:1 to 4.3:1 as the arm was elevated. Heavy shoulder loading resulted in an increasing scapulohumeral rhythm from 1.9:1 to 4.5:1 as the arm was elevated. The results suggest that the historical assumption of a simple linear 2:1 scapulohumeral rhythm ratio may be overly simplistic and may not accurately describe the scapulohumeral rhythm under varying dynamic conditions. Therapists need to understand the normal changing relationships of the scapulohumeral rhythm under different conditions for accurate interpretation of clinical observations.