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Biomedical subjects

J F Lehmann

Publications and source records attributed to J F Lehmann.

At least 19 recordsLinked to original sources
PubMed1992

Effect of lower limb on body propulsion.

The purpose of this study was to analyze and compare the effects of the leg during swing and stance phases of forward propulsion of the body for both men and women. Twelve able-bodied subjects, six men and six women, were studied with a Vicon(a) gait-analysis system. A two-dimensional, sagittal-plane biomechanical analysis featuring a link-segment model was used to determine the force at the hip in the horizontal direction. Integrating this force curve over time during the swing and stance gait phases produced linear impulses, representing swing and stance contributions to the propulsion of the body, and it allowed quantitative comparisons using student t and Fisher tests. The deceleration of the swing leg was found to be the major contributor to the forward propulsion of the body. The stance leg initially exerted the major restraining or negative impulse during early stance; then it generated a positive impulse during push-off in late stance. A typical pattern of gait impulses was defined for normal gait. Male and female gait impulses were not significantly different for all gait phases.

Adult↗
PubMed1991

Quantitative measurement of spasticity in children with cerebral palsy.

Spasticity was quantified in nine children with spastic diplegia, using a sinusoidal displacement of the foot at frequencies from 3 to 12Hz. Ankle-joint stiffness was separated into elastic (energy-storing) and viscous (energy-dissipating) components. 'Path length' was used to represent the variation in stiffness over this frequency range. Compared with 11 unaffected children, a significant difference in path lengths was demonstrated for the children with spasticity. An age-dependent effect was demonstrated when path lengths of unaffected children were compared with those of 10 unaffected adults. A modified path-length measure is proposed which minimizes age dependency, yet enables detection of spasticity. Passive stiffness properties of unaffected adults showed higher elastic stiffness, viscosity and friction than unaffected children. A method was developed to evade the need for temporary nerve blocks to calculate inerital properties of the foot in persons with spasticity.

Biomechanical Phenomena↗
PubMed1991

Footwear and posture. Compensatory strategies for heel height.

The belief that wearing high-heeled shoes increases lumbar lordosis is firmly ingrained in clinical folklore. Proponents of negative heel footwear argue that because high positive heels increase the lumbar lordosis, negative heels will decrease the lumbar lordosis. Quantitative documentation of the assumption regarding high heels is not to be found in the literature, although sporadic attempts to prove this assumption have been made throughout the 20th Century. Although other effects, such as decreased gait speed and step length, and increased knee flexion at heel strike have been found in more than one study, no increase in lumbar lordosis has been found. Where an actual decrease in lordosis has been found, authors tend to explain it away as inconsistent with what every clinician feels that he or she has observed. We felt it appropriate, then, to conduct both a static and a dynamic study to assess the effects of heel height on lumbar spine and lower limb joint kinematics in the sagittal plane, as well as other strategies to compensate for heel height. The results indicate that the greatest compensation is at the ankle and knee. Where a significant effect occurred in the lumbar spine (males, dynamic study), high heels decreased the lumbar lordosis, i.e., resulted in less swayback rather than more.

Adolescent↗
PubMed1990

Spasticity in spinal cord injured persons: quantitative effects of baclofen and placebo treatments.

Spasticity commonly occurs after a spinal cord injury and is characterized by increased resistance to passive movement of peripheral joints. This study examined the effect of an antispasticity medication on stiffness from the myotatic reflex response generated by passive sinusoidal ankle motion. A repeated measures, multiple base-line, single-subject, double-blind design was employed. The independent variable was spasticity medication treatment, where the levels were 40 mg/day and 80 mg/day of baclofen v placebo treatment. Viscous and elastic stiffness measurements were taken at the ankle joint during a placebo base-line phase and during treatment with baclofen for five adult males with traumatic spinal cord injuries. Ankle sinusoidal oscillation frequencies were from 3 to 12 Hz during test sessions. Mean viscous and elastic stiffness scores for all frequencies were calculated for each phase of the study. Randomization tests of mean changes in stiffness measurements between each treatment phase of the study failed to provide any convincing evidence of a significant treatment effect for reduction of spasticity in the traumatic spinal cord injured subjects studied. Further testing is needed to exclude potential confounding factors before this conclusion can be confirmed. The results suggest that baclofen is not a universal treatment of choice for all individuals with spasticity resulting from traumatic spinal cord injury.

Adult↗
PubMed1990

Quantitative evaluation of sway as an indicator of functional balance in post-traumatic brain injury.

The test of sway, using different conditions of stance with measurements of the average radial deviation of the center of pressure and its path length of sway per unit of time, has been shown to be a useful clinical tool in determining balance problems in traumatic brain injury (TBI) patients. Normative values were established to determine if an individual patient's sway values fell within the normal range (mean +/- 2SD). The tests have shown good test-retest reliability for TBI patients. In addition, it has been shown that the sensitivity of the test is sufficient to identify changes in patients' performances as their clinical conditions change. It has been demonstrated that the different stance conditions of the battery of tests become progressively more difficult to perform (from comfortable stance, eyes open and eyes closed, through narrow stance, eyes open and eyes closed, to tandem stance with right or left foot forward, eyes open and eyes closed). By using these subtests, it is easy to distinguish between the performances of able-bodied patients and TBI patients with very mild balance problems. The validity of the measure has been documented by correlating the sway performance with clinical functional performance tests. The test performance also correlates with the patient's own assessment of his or her gait difficulties. The limited data available suggest that the test of sway relates difficulties in static balance to the frequency of falls. Finally, subtests permit identification of specific problems in maintaining balance as a basis for therapeutic intervention.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1990

Influence of muscle cooling on the viscoelastic response of the human ankle to sinusoidal displacements.

The changes in passive mechanical muscle properties due to cooling of the calf in healthy human volunteers were investigated. The technique, using sinusoidal driving of the foot, permitted the separation of muscle stiffness response into its elastic and viscous components. Cooling the calf with ice for 30 minutes increases the rate of change of elastic stiffness with frequency, and it increases the frictional stiffness over a frequency range of 3 to 12Hz. Such cooling would produce an estimated 3% to 10% increase in total stiffness, on average, in a spastic person. This increase in stiffness would counteract reductions in total stiffness achieved during the application of cryotherapy to relieve spasticity. However, one could expect that for a clinically significant reduction of spasticity, the increase in passive stiffness of the muscle generated by cooling would be largely overshadowed by the decrease in reflex reactivity.

Adult↗
PubMed1978

Temperatures in human thighs after hot pack treatment followed by ultrasound.

Temperature distributions were measured in the anterior thigh of human volunteers after preheating with a hot pack followed by ultrasound, a frequently used therapeutic procedure. The skin surface temperature is elevated by this procedure but the highest temperature is still produced at the bone-muscle interface at the end of the treatment session.

Adult↗
PubMed1978

Knee lock device for knee ankle orthoses for spinal cord injured patients: an evaluation.

The effect of a specially designed knee lock in a knee ankle orthosis was studied in 2 able-bodied volunteers and in 2 patients with spinal cord lesions. This lock allows the knee to bend during the swing phase but locks the knee securely during the stance phase. The device is intended to improve gait pattern and reduce oxygen consumption more than a standard knee lock which keeps the knee straight throughout the entire gait cycle. Energy savings with the knee locking mechanism were significant only at ambulation rates at or above 73 meters/min, a speed which could only be attained by able-bodied subjects. To achieve such high rates of ambulation a patient's hip flexors must be strong; yet a knee ankle orthosis is required only when the patient's knee extensors are weak. In patients with spinal cord injuries, this pattern of muscle strength is rarely encountered. The innervation of hip flexors or knee extensors overlaps, so voluntary control of these muscles will either be present or absent for both muscle groups. Therefore, most spinal cord injured persons who need a knee orthosis would not greatly benefit from this locking mechanism. There may be other conditions in which this device will prove valuable.

Adult↗
PubMed1978

Cancer rehabilitation: assessment of need, development, and evaluation of a model of care.

A sample of 805 cancer patients, comparable to but not identical with a national study, was screened to identify: rehabilitation problems encountered at different cancer sites; the need for rehabilitation services; and gaps in the delivery of rehabilitation care. Significant numbers of rehabilitation problems were found that could be improved by rehabilitation care. Psychologic problems were commonly encountered and seemed more severe in patients with physical disabilities; these patients have to make adjustments to both life-threatening disease and to a disabling condition. The findings suggest a need for psychosocial support services on any oncology service; where cancer is associated with significant physical disability, a comprehensive rehabilitation team with psychologic management capability is often needed. Primary barriers to optimal delivery of rehabilitation care are the lack of identification of patient problems and/or lack of appropriate referral by physicians unfamiliar with the concept of rehabilitation. Health care financial support for the patients in the sample came primarily from private insurance, Medicare and Medicaid; financial support from the patient's family held up well even in the advanced stages of the disease. A model of rehabilitation care delivery was established and implemented, with the result being that gaps and barriers to rehabilitation service delivery disappeared rapidly.

Activities of Daily Living↗
PubMed1978

Fibrous muscular contractures: treatment with a new direct contact microwave applicator operating at 915 MHz.

A patient having bilateral contractures of the rectus femoris and brachial biceps muscles due to pentazocine injection was treated with a regime of heat and stretch. Heat was provided by a new air cooled direct contact applicator operating at 915 MHz. Stretch was applied by adding weights to a cable which was attached to the arm or leg to be stretched. While the left and right elbows which were limited by the contracted biceps were not stretched sufficiently to achieve a normal range of motion, the rectus femoris muscle on both sides did achieve a normal range of motion.

Contracture↗
PubMed1977

Pneumatic and standard double upright orthoses: comparison of their biomechanical function in three patients with spinal cord injuries.

A detailed analysis of the biomechanical and physiological function of pneumatic orthoses comparing them to the standard double upright knee ankle orthoses was performed in three patients with different lesion levels. The results suggest that the main value of the long pneumatic orthosis is for early mobilization of the patient. In addition, the long pneumatic orthosis provides hip and trunk stabilization for marginal walkers who walk for exercise purposes. It is likely that most long-term functional ambulators will choose the standard knee ankle orthosis (KAO). The study dose not represent a statistical sample; therefore generalization must be limited.

Adult↗
PubMed1976

Heat and stretch procedures: an evaluation using rat tail tendon.

This study evaluated various methods of applying force to collagenous tissue at various temperatures to produce permanent elongation, using rat tail tendon as the tissue model. A materials testing machine was used to measure the forces applied and the resulting elongation produced by differing procedures. Short-term vigorous stretching and prolonged moderate stretching were compared at 37 C. The effect of heating tissue prior to applying force was evaluated, and the effect of using a prolonged application of low force was demonstrated. The data showed that the low force, long duration procedure was very effective at producing residual elongation. Elevating tissue temperature and maintaining it prior to applying force was found to cause significantly less damage; and finally, the lower loads applied at elevated temperatures for prolonged periods were found to produce significantly greater residual elongation.

Animals↗
PubMed1976

Mechanical work and fatigue: their roles in the development of muscle work capacity.

To compare the effects of mechanical work versus fatigue on the improvement of work capacity of muscle, young, healthy men were selected to life a 45-pound weight with their quadriceps for 30 sessions, followed by 5 sessions of testing. The study consisted of two phases. Subjects in the first phase did equal amounts of mechanical work with both quadriceps, but had different amounts of fatigue from side to side because the rate of work was different. Subjects in the second phase fatigued both quadriceps, but one quadriceps was fatigued with a rest period between contraction cycles, and one was fatigued without a rest period, thus allowing the side with the rest cycle to do more mechanical work. To test the relative effects of training, a transfer-of-training design was used in both phases. The results suggest that fatigue, defined operationally as the inability or unwillingness of the subject to continue the prescribed task under given reinforcement conditions, plays a larger role in the development of work capacity of muscle than the amount of mechanical work per se.

Adolescent↗
PubMed1976

Restraining forces in various designs of knee ankle orthoses: their placement and effect on the anatomical knee joint.

A biochemical evaluation was conducted on double upright knee ankle orthoses, which were instrumented with strain gauge transducers to determine the magnitudes of the restraining forces exerted on the leg. Measurements were made on six commonly used designs of orthoses worn by spinal cord injured persons ambulating with a swing-through gait. The measurements were used to determine distribution of forces on the limb as well as their effect on anatomical knee shear. Based on the experimental data, the following basic principles of optimal orthosis design were identified: The forces required to stabilize the knee should be minimized by applying the stabilizing force as close as possible to the knee center, and by maintaining the anatomical knee as straight as possible. When the major portion of the knee stabilizing force is applied below the knee, the shear on the anatomical knee structures is markedly reduced. Further, the stabilizing forces should be well distributed over tolerant areas.

Ankle Joint↗
PubMed1976

Undergraduate education in rehabilitation medicine: trends in curriculum development and the impact on specialty manpower and delivery of service.

One hundred thirteen medical schools which offered full degree programs were identified and surveyed by questionnaires to obtain information which identified the existence, characteristics and involvement of physical medicine or rehabilitation medicine programs. The survey also attempted to identify specific changes which have occurred in undergraduate medical education in rehabilitation medicine since the Commission of Education and Rehabilitation Medicine survey of 1963-64. The results suggest that growth of the programs has not followed the expansion in the number of medical schools nor in the number of students enrolled. The programs have however, improved their administrative standing and involvement in medical schools. The impact on the undergraduate medical student is not satisfactory as judged by elective enrollment and recruiting of residents. Lack of funding was found to be one of the major obstacles to curriculum development, along with a marked shortage of academic physiatrists. The impact of the changes in undergraduate medical school curricula on rehabilitation medicine has produced considerable conjoint teaching in conjunction with a large number of basic science and clinical departments.

Curriculum↗
PubMed1976

Craig-Scott orthosis: a biochemical and functional evaluation.

The Craig-Scott double upright knee ankle orthosis was subjected to a biomechanical evaluation which included analysis of the force interaction with the supported limb and a functional evaluation. The results were compared with data previously determined from biomechanical evaluations of other common orthoses. In the Craig-Scott design, the single application of the knee stabilizing force below the knee concentrates this force in a relatively small bony area, sometimes exceeding tolerance. This might be avoided by using a tibial closure with patellar tendon bearing features. The design was found to produce relatively low anatomic knee shear. In functional aspects such as donning, doffing, transfers and ambulation, the orthosis is essentially equivalent to other double upright designs. The rigidity of the orthosis with only a tibial band closure and a bail connecting the uprights was determined to be adequate. The limited number of bands and closures provides some advantages in reduced donning and doffing time; however, in the absence of posterior closures below the knee, the orthosis had a tendency to slide forward off the leg when transferring. This disadvantage was eliminated by adding a soft posterior closure below the knee, which produced a minimal increase in donning and doffing times.

Animals↗