How do strength, sensation, spasticity and joint individuation relate to the reaching deficits of people with chronic hemiparesis?

Hemiparetic subjects present with movement deficits including weakness, spasticity and an inability to isolate movement to one or a few joints. Voluntary attempts to move a single joint often result in excessive motion at adjacent joints. We investigated whether the inability to individuate joint movements is associated with deficits in functional reaching. Controls and hemiparetic subjects performed two different reaching movements and three individuated arm movements, all in the parasagittal plane. The reaching movements were a sagittal 'reach up' (shoulder flexion and elbow flexion) and 'reach out' (shoulder flexion and elbow extension). Joint individuation was assessed by getting each subject to perform an isolated flexion-extension movement at each of the shoulder, elbow and wrist joints. In addition, we measured strength, muscle tone and sensation using standard clinical instruments. Hemiparetic subjects showed varying degrees of impairment when performing reaching movements and individuated joint movements. Reaching impairments (hand path curvature, velocity) were worse in the reach out versus the reach up condition. Typical joint individuation abnormalities were excessive flexion of joints that should have been held fixed during movement of the instructed joint. Hemiparetic subjects tended to produce concurrent flexion motions of shoulder and elbow joints when attempting any movement, one explanation for why they were better at the 'reach up' than the 'reach out' task. Hierarchical regression analysis showed that impaired joint individuation explained most of the variance in the reach path curvature and end point error; strength explained most of the variance in reaching velocity. Sensation also contributed significantly, but spasticity and strength were not significant in the model. We conclude that the deficit in joint individuation reflects a fundamental motor control problem that largely explains some aspects of voluntary reaching deficits of hemiparetic subjects.

Effect of active limb movements on symptoms in patients with low back pain.

STUDY DESIGN: A descriptive, correlational study of patients with mechanical low back pain (LBP). OBJECTIVES: To assess the effect of active limb movements on symptoms in patients with LBP and to examine the relationship between symptoms with limb movements and select patient characteristics. BACKGROUND: Limb movements result in forces applied to the spine and, thus, may be important in the examination and treatment of patients with LBP. METHODS AND MEASURES: A total of 188 people with LBP, 84 men and 104 women, participated in a standardized examination. Six of the items required patients to move their limbs and note LBP symptoms as increased, remained the same, or decreased. The prevalence of various symptom responses with each limb movement test was calculated. Relationships between patient characteristics and reports of increased symptoms were examined with Cochran's linear trend statistic and the Spearman and Pearson correlation coefficients. Differences in characteristics of patients with and without increased symptoms were examined with chi2 test, Mann-Whitney U test, or Student's t test for independent groups. RESULTS: An increase in symptoms was reported by 149 patients with at least 1 of the limb movement tests, and 3 of the patients reported a decrease in symptoms. Across the patient sample, the mean number of limb movement tests for which symptoms were reported as increased was 2.30 +/- 1.64. Patients with an increase in symptoms reported higher average pain intensity the week prior to the examination (median = 2; range: 1-5) and higher functional disability (mean = 0.25; SD = 0.15) than those without a change in symptoms (pain intensity: median = 1; range: 0-2 and functional disability: mean = 0.16; SD = 0.12). The correlation between the number of increased symptoms and the person's average pain intensity was r = 0.23; the correlation with the functional disability score was r = 0.36. Patients with a history of LBP tended to report an increase in symptoms with more of the limb movement tests (mean = 3.5; SD = 1.40) than those without a previous history of LBP (mean = 2.0; SD = 1.11). CONCLUSIONS: Active limb movements performed during the examination primarily resulted in increased LBP symptoms. The presence and number of increased symptoms with the active limb movements was related to the patient's report of average pain intensity and functional disability. Tests of symptoms with active limb movements may provide insight into factors contributing to a LBP problem, as well as information to guide the treatment of patients with LBP.

Use of a classification system to guide nonsurgical management of a patient with chronic low back pain.

BACKGROUND AND PURPOSE: This case report describes the use of a classification system in the evaluation of a patient with chronic low back pain (LBP) and illustrates how this system was used to develop a management program in which the patient was instructed in symptom-reducing strategies for positioning and functional movement. CASE DESCRIPTION: The patient was a 55-year-old woman with a medical diagnosis of lumbar degenerative disk and degenerative joint disease from L2 to S1. Rotation with extension of the lumbar spine was found to be consistently associated with an increase in symptoms during the examination. Instruction was provided to restrict lumbar rotation and extension during performance of daily activities. OUTCOMES: The patient completed 8 physical therapy sessions over a 3-month period. Pretreatment, posttreatment, and 3-month follow-up modified Oswestry Disability Questionnaire scores were 43%, 16%, and 12%, respectively. DISCUSSION: Daily repetition of similar movements and postures may result in preferential movement of the lumbar spine in a specific direction, which then may contribute to the development, persistence, or recurrence of LBP. Research is needed to determine whether patients with LBP would benefit from training in activity modifications that are specific to the symptom-provoking movements and postures of each individual as identified through examination.

Hip abductor weakness in distance runners with iliotibial band syndrome.

OBJECTIVE: To examine hip abductor strength in long-distance runners with iliotibial band syndrome (ITBS), comparing their injured-limb strength to their nonaffected limb and to the limbs of a control group of healthy long-distance runners; and to determine whether correction of strength deficits in the hip abductors of the affected runners through a rehabilitation program correlates with a successful return to running. DESIGN: Case series. SETTING: Stanford University Sports Medicine Clinics. PARTICIPANTS: 24 distance runners with ITBS (14 female, 10 male) were randomly selected from patients presenting to our Runners' Injury Clinic with history and physical examination findings typical for ITBS. The control group of 30 distance runners (14 females, 16 males) were randomly selected from the Stanford University Cross-Country and Track teams. MAIN OUTCOME MEASURES: Group differences in hip abductor strength, as measured by torque generated, were analyzed using separate two-tailed t-tests between the injured limb, non-injured limb, and the noninjured limbs of the control group. Prerehabilitation hip abductor torque for the injured runners was then compared with postrehabilitation torque after a 6-week rehabilitation program. RESULTS: Hip abductor torque was measured with the Nicholas Manual Muscle Tester (kg), and normalized for differences in height and weight among subjects to units of percent body weight times height (%BWh). Average prerehabilitation hip abductor torque of the injured females was 7.82%BWh versus 9.82%BWh for their noninjured limb and 10.19%BWh for the control group of female runners. Average prerehabilitation hip abductor torque of the injured males was 6.86%BWh versus 8.62%BWh for their noninjured limb and 9.73%BWh for the control group of male runners. All prerehabilitation group differences were statistically significant at the p < 0.05 level. The injured runners were then enrolled in a 6-week standardized rehabilitation protocol with special attention directed to strengthening the gluteus medius. After rehabilitation, the females demonstrated an average increase in hip abductor torque of 34.9% in the injured limb, and the males an average increase of 51.4%. After 6 weeks of rehabilitation, 22 of 24 athletes were pain free with all exercises and able to return to running, and at 6-months follow-up there were no reports of recurrence. CONCLUSIONS: Long distance runners with ITBS have weaker hip abduction strength in the affected leg compared with their unaffected leg and unaffected long-distance runners. Additionally, symptom improvement with a successful return to the preinjury training program parallels improvement in hip abductor strength.

Effect of knee and hip position on hip extension range of motion in individuals with and without low back pain.

STUDY DESIGN: A 2-group, nonrandomized, mixed design with 1 between-subjects factor (group) and 2 within-subjects factors (knee and hip position). OBJECTIVES: To determine the amount of passive hip extension during changes in the knee angle in the sagittal plane, and the hip angle in the frontal plane in back-healthy (BH) subjects and subjects with low back pain (LBP). BACKGROUND: Information regarding the specific contributions of hip flexor muscles to limitations in hip extension range of motion (ROM) is necessary for the prescription of appropriate treatment. METHODS AND MEASURES: Thirty-five BH subjects (24 women and 11 men, mean age = 31.37 +/- 11.36) and 10 subjects with LBP (6 women and 4 men, mean age = 33.70 +/- 9.31) participated in the study. The passive length of the one- and two-joint hip flexor muscles was tested in 4 different conditions in which the positions of the knee and the hip were varied. The knee was positioned passively in full extension or 80 degrees of flexion while the hip was positioned passively in zero abduction or full abduction. RESULTS: Subjects with LBP displayed less passive hip extension than BH subjects (LBP, -5.61 degrees +/- 4.30; BH, -2.57 degrees +/- 4.18). Both groups had less hip extension when the knee was in flexion of 80 degrees than when the knee was fully extended (flexed, -5.51 +/- 4.50; extended, -0.98 degrees +/- 4.65), and when the hip was in zero hip abduction than when the hip was fully abducted (zero, -7.55 degrees +/- 5.03; full, 1.06 degrees +/- 4.31). The contribution of the different hip flexors to a hip extension limitation differed between BH and subjects with LBP. BH subjects demonstrated an effect of knee angle on hip extension when the hip was in zero abduction (flexed, -11.43 degrees +/- 5.81; extended, -2.49 degrees +/- 5.39), but not when the hip was in full abduction (flexed, 1.74 degrees +/- 3.91; extended, 1.89 degrees +/- 3.94). Subjects with LBP demonstrated an effect of knee angle on hip extension when the hip was in zero abduction (flexed, -12.60 degrees +/- 4.91; extended, -6.65 degrees +/- 5.03) and when the hip was in full abduction (flexed, -3.10 degrees +/- 5.53; extended, -0.10 degrees +/- 5.18). CONCLUSIONS: The results of this study provide evidence that changing the knee joint angle in the sagittal plane and the hip joint angle in the frontal plane, during the hip flexor length test, can affect the amount of passive hip extension ROM. The contribution of specific hip flexor muscles to a hip extension limitation may differ depending on the individual's movement dysfunction. Modifying the hip flexor length test, as described, should provide information about the specific muscles contributing to a hip joint extension limitation.

Passive ankle stiffness in subjects with diabetes and peripheral neuropathy versus an age-matched comparison group.

BACKGROUND AND PURPOSE: Patients with diabetes mellitus and peripheral neuropathy (DM and PN) often complain of joint stiffness. Although stiffness may contribute to some of the impairments and functional limitations found in these patients, it has not been quantified in this population. The purpose of this study was to quantify and compare passive ankle stiffness and dorsiflexion (DF) range of motion in subjects with DM and PN versus an age-matched comparison group. SUBJECTS: Thirty-four subjects were tested (17 subjects with DM and PN and 17 subjects in an age-matched comparison group). There were 10 male subjects and 7 female subjects in each group. METHODS: A Kin-Com dynamometer was used to measure passive plantar flexor torque as each subject's ankle was moved from plantar flexion into dorsiflexion at 60(/s. The following variables were compared using a Student t test: initial angle (angle of onset of plantar flexor torque), maximal dorsiflexion angle, plantar flexor muscle excursion (difference between initial angle and maximal dorsiflexion angle), slope of the first half of the plantar flexor torque curve (stiffness 1 measurement), and slope of the second half of the plantar flexor torque curve (stiffness 2 measurement). RESULTS: The subjects with DM and PN had smaller maximal dorsiflexion angles and less plantar flexor muscle excursion than the comparison group. There was no difference in initial angle, stiffness 1 measurement, or stiffness 2 measurement. CONCLUSION AND DISCUSSION: Although the subjects with DM and PN had less dorsiflexion range of motion than did the comparison group, there was no difference in stiffness between the groups. This finding suggests that people with DM and PN have "short" versus "stiff" plantar flexor muscles.

Postural synergies associated with a stepping task.

BACKGROUND AND PURPOSE: Synergistic relationships among multiple muscle components are thought to exist to simplify control of posture and movement. The purpose of this study was to examine the extent to which children, young adults, and older adults exhibit consistent sequences of postural muscle activation when lifting the right foot onto a step from a standing position. SUBJECTS: Twenty subjects without known impairments of the neuromuscular system (10 male, 10 female) in each of 3 age groups--children (8-12 years), young adults (25-35 years), and older adults (65-73 years)--participated. METHODS: A pressure switch taped to the subject's right foot was used to determine movement onset and offset. Latencies of muscle activation were determined using surface electromyography. A preferred postural synergy was defined as the sequence of postural muscle activation observed during the majority of trials for each subject. RESULTS: Mean movement times did not differ among age groups. Although the left tibialis anterior (TA) muscle was the first of the postural muscles activated in 93% of the trials, subjects displayed considerable variability in the subsequent order of postural muscle activation. Across subjects, a total of 14 different preferred postural synergies were observed. Age groups did not differ in the number of different synergies. CONCLUSION AND DISCUSSION: Early TA activation may reflect biomechanical constraints of the stepping task, producing forward displacement of the center of mass over the changing base of support. The fact that subjects of all ages were quite variable in the specific sequences of muscles activated subsequent to the TA suggests that, for this type of task, therapists should not focus their interventions on facilitating execution of particular synergy patterns.

Reliability of physical examination items used for classification of patients with low back pain.

BACKGROUND AND PURPOSE: The purpose of this study was to examine the interrater reliability of measurements obtained by examiners administering tests proposed to be important for classifying low back pain (LBP) problems. SUBJECTS: Ninety-five subjects with LBP (41 men, 54 women) and 43 subjects without LBP (17 men, 26 women) were examined by 5 therapists trained in the techniques used. METHODS: A manual was developed by the first author that described the clinical examination procedures. The therapists were trained by the first author in the test procedures and definitions. The training included instruction through videotapes, practice and a written examination. Each examination was conducted by a pair of therapists. Within a pair, a therapist was the primary examiner for half of the subjects and an observer was the primary examiner for half of the subjects. Examination findings were recorded independently, without discussion. RESULTS: Percentage of agreement and generalized kappa coefficients were used to analyzed the data. Kappa values were > or = .75 for all 28 items related to the symptoms elicited and > or = .40 for 72% of the 25 items related to alignment and movement. CONCLUSION AND DISCUSSION: The results suggest that experienced therapist who had trained together were able to agree on the results of examinations and obtain an acceptable level of reliability. Future work should focus on testing of reliability when more than one therapist performs the examination and when therapist not trained by the test developer to administer the examination perform the tests. [Van Dillen LR, Sahrmann SA, Norton BJ, et al. Reliability of physical examination items used for classification of patients with low back pain.

Age Group Differences in Postural Adjustments Associated With a Stepping Task.

In this study, differences among age groups in the postural adjustments associated with a stepping task were identified. Twenty subjects from each of 3 age groups, children (8-12 years), young adults (25-35 years), and older adults (65-73 years), performed the task in 2 movement contexts: place and step. In place, the subject simply lifted the foot and placed it on the step. In step, the subject lifted the foot, placed it on the step, and stepped up onto the step. Latencies of postural and focal muscle activation were determined by using surface electromyography and pressure switches. Center of pressure (CP) data were obtained by using a force platform. Subjects in all 3 age groups consistently demonstrated postural adjustments before movement initiation. Children displayed longer postural latencies than young adults as well as disproportionately large values for CP path length. Older adults showed prolonged postural-focal latencies and decreased CP excursions compared with the 2 younger age groups. These results suggest that maturation of coordination between posture and movement may not be fully complete in 8- to 12-year-olds and that increased restraint characterizes the performance of postural adjustments in healthy persons over 65 years of age.

Relationship of plantar-flexor peak torque and dorsiflexion range of motion to kinetic variables during walking.

BACKGROUND AND PURPOSE: Limited ankle plantar-flexor moments and power during walking have been documented in several patient populations and are believed to contribute to gait deviations. The primary purpose of this study was to determine the relationship of plantar-flexor peak torque (PFPT) and dorsiflexion range of motion (ROM) to peak ankle moments and power during walking in a group of subjects without diabetes mellitus (DM) and in a group of subjects with DM and associated peripheral neuropathies. SUBJECTS: Nineteen subjects, 9 with DM and associated peripheral neuropathies (mean age = 58 years, SD = 14, range = 35-75 years) and 10 without DM (mean age = 57 years, SD = 11, range = 37-68 years), were evaluated. METHODS: The following data were collected on all subjects: PFPT, dorsiflexion ROM, and ankle moments and power during walking (using a two-dimensional link-segment model). Hierarchical multiple regression was used for data analysis. RESULTS: Plantar-flexor peak torque made substantial contributions to the ankle moment (40%) and ankle plantar-flexor power (53%) during walking. There also was a high correlation between PFPT and dorsiflexion ROM (r = .78) and between dorsiflexion ROM and ankle power (r = .72). CONCLUSION AND DISCUSSION: Plantar-flexor peak torque and dorsiflexion ROM are interrelated and appear to be important factors that contribute to ankle plantar-flexor moments and power during walking. This finding suggests that increasing PFPT and dorsiflexion ROM may help decrease gait deviations such as decreased step length and walking speed. When increasing PFPT is not possible, the natural occurrence of limited dorsiflexion ROM may help to maximize ankle moments during walking. Further research is needed to test whether these proposed treatment strategies can have a clinically useful effect. [Mueller MJ, Minor SD, Schaaf JA, et al. Relationship of plantar-flexor peak torque and dorsiflexion range of motion to kinetic variables during walking.

Differences in the gait characteristics of patients with diabetes and peripheral neuropathy compared with age-matched controls.

BACKGROUND AND PURPOSE: Patients with diabetes and peripheral neuropathy have a high incidence of injuries while walking. Biomechanical analysis of their walking may lead to treatments to reduce these injuries. The purpose of this study was to compare (1) the gait characteristics, (2) the plantar-flexor peak torques, and (3) the ankle range of motion of subjects with diabetes mellitus (DM) and peripheral neuropathy with those of age-matched controls. SUBJECTS: Twenty subjects, 10 with DM and a history of peripheral neuropathy (DM group) (mean age = 58 years, SD = 15, range = 35-75) and 10 subjects without diabetes (NODM group) (mean age = 57 years, SD = 11, range = 37-68), were evaluated. METHODS: The following data were collected on all subjects: ankle joint mobility, plantar-flexor peak torque (ankle strength), kinematics of the trunk and lower extremity during normal walking, and ground reaction forces. Moments and power at the ankle, knee, and hip during walking were calculated using a two-dimensional link-segment model. RESULTS: The DM group subjects showed less ankle mobility, ankle moment, ankle power, velocity, and stride length during walking than the NODM group subjects. A significant decrease in ankle strength and mobility appeared to be the primary factor contributing to the altered walking patterns of the DM group. CONCLUSION AND DISCUSSION: The DM group subjects appeared to pull their legs forward using hip flexor muscles (hip strategy) rather than pushing the legs forward using plantar-flexor muscles (ankle strategy), as seen in the NODM group subjects. Implications for treatment are presented to attempt to reduce the number of injuries during walking in patients with DM and peripheral neuropathy.

Patterns of hip rotation range of motion: a comparison between healthy subjects and patients with low back pain.

The purpose of this study was to characterize and classify the prevalence of passive hip rotation range-of-motion (ROM) asymmetry in healthy subjects (n = 100) and in patients with low back dysfunction (n = 50). We categorized the subjects of both groups as having one of three patterns of hip rotation. Pattern IA existed when all ROM measurements were equal (within 10 degrees). Pattern IB existed when total medial and lateral rotation were equal, but one or more of the individual measurements were unequal. Pattern II existed when total medial rotation ROM was greater than total lateral rotation ROM. Those subjects with total lateral rotation ROM greater than total medial rotation ROM demonstrated pattern III. The distribution of subjects among the ROM pattern categories was significantly different in the patient and healthy subject groups. The frequency of occurrence of pattern III was greater in the patient group than in the healthy subject group. These results suggest an association between hip rotation ROM imbalance and the presence of low back pain.

Diagnosis by the physical therapist--a prerequisite for treatment. A special communication.

A critical step for the future of the profession of physical therapy is the development of diagnostic categories. The purpose of this communication is to clarify issues regarding the role of the physical therapist in developing classifications of the signs and symptoms that are identified by the therapist's examinations and tests. A primary premise is that treatment should be based on the diagnosis derived by the physical therapist because the medical diagnosis does not provide sufficient direction. A generic definition is given as a guide for development of diagnostic classification schemes. Arguments are provided that these diagnoses will 1) clarify practice, 2) provide an important means of communication with colleagues and consumers, 3) classify and group conditions that can direct research and assessment of treatment effectiveness, and 4) reduce the tendency toward cultism associated with practice based almost entirely on treatment approaches.

Length and circumference measurements in one-joint and multijoint muscles in rabbits after immobilization.

In this article, we compared changes in the length and circumference of the soleus and the plantaris muscles in rabbits. The rabbits were assigned to a nonimmobilized external control group (n = 4), an experimental shortened-position group (n = 10), or an experimental lengthened-position group (n = 9). One hind limb of each animal in the experimental groups was immobilized in a cast for four weeks to put the muscles in either a shortened or lengthened position. The contralateral limb served as an internal control for the animals in the experimental groups. After the immobilization period, the limbs were fixed in situ, the muscles were dissected, and length and circumference measurements were taken. In both experimental conditions, the immobilized soleus muscles were shorter than their contralateral counterparts (p less than .05); the length of the plantaris muscles did not change. The immobilized muscles had decreased circumference values regardless of the immobilization angle. When compared with the control condition, the shortened soleus muscles had a greater decrease in circumference than did the plantaris muscles. More connective tissue was observed in the muscle bellies of the soleus after immobilization than in the plantaris. Similar significant changes (p less than .05) were found in the nonimmobilized limbs of the animals in the experimental groups. Specifically, the soleus muscles demonstrated length and circumference changes, whereas the plantaris muscles showed changes only in circumference. These findings suggest that when a weight-bearing limb is immobilized, adaptations in gross muscle length and circumference are to be expected in the involved and uninvolved limbs. An assessment of similar adaptations in humans should be a part of the evaluation during recovery.

Motor cortical neuronal activity patterns in monkeys performing several force tasks at the ankle.

Normal rhesus monkeys were conditioned at light signals to exert forces with both feet on fixed foot bars. The tasks included small and large sustained forces in plantar and dorsiflexion directions and large phasic forces in both directions. The tasks were selected to relate to behaviors known to be impaired in the upper motor neuron syndrome. Extracellular recordings were made from 226 area 4 motor cortex units (MCUs) in the hindlimb region of area 4. Ninety percent of the MCUs showed increased activity temporally related to force and EMG changes; 10% showed decreased activity exclusively. The 203 MCUs showing increased activity differed in their directional preference: half were active only in relation to development of force in one direction (unidirectional) and the remainder with forces in both directions (bidirectional). Only 28/101 of the bidirectional units were symmetric (equal activity with force in both directions). The majority were asymmetric with a greater degree of activity in one direction. Both unidirectional and bidirectional (symmetric and asymmetric) MCUs often developed increased activity not only with agonist force production but also with force relaxation in the antagonist muscles. Seventy-eight percent of the MCUs showing increased activity had phasic discharge qualities, lacking sustained activity during the prolonged force holds. Thirty-eight percent of the MCUs showing increased activity were more active with larger force, and 14% with smaller force; 48% had closely similar activity with both force levels. None of these characteristics was related to directionality. A spectrum of MCU behaviors was found that ranged in complexity from units which increased or decreased discharge with force in one direction to those responding with force production and force relaxation in both directions.

Electromyographic study of the relationship between hamstring and abdominal muscles during a unilateral straight leg raise.

The purposes of this study were 1) to assess the relative participation of the hip extensor and abdominal musculature during unilateral straight leg raising in the naive subject and 2) to examine quantitatively alterations in the pattern of pelvic stabilization when the subject was instructed to relax the contralateral extremity. Surface electrodes were used to record bilaterally the electromyographic activity of the rectus abdominus, external oblique, and medial hamstring muscles. Each healthy subject performed a unilateral straight leg raise three times in each of two modes, Preferred and Relaxed. The electromyographic values for each muscle were normalized to a maximum isometric contraction and analyzed using a three-factor (2 X 2 X 2) mixed design analysis of variance. Results indicate that 9 of the 11 subjects used the tested medial hamstrings and abdominal muscles during a unilateral straight leg raise performed in the Preferred Mode. When instructed to relax the contralateral extremity for the Relaxed Mode, abdominal muscle activity increased significantly (p less than .01). The findings indicate that although most subjects normally stabilize with the contralateral extremity during a unilateral straight leg raise, they can consciously alter the pattern.

Review of length-associated changes in muscle. Experimental evidence and clinical implications.

Movement dysfunction that may be caused by length-associated changes in muscle is a problem of people treated by physical therapists. The purpose of this article is to review the literature related to length-associated changes in muscle. An analysis of length-associated changes in animal and human studies is presented. The methods used to produce the changes in animals are discussed, and the clinical implications of the length-associated changes in muscle are suggested.

Stretch reflex of the biceps and brachioradialis muscles in patients with upper motor neuron syndrome.

The position of elbow flexion commonly observed in patients with upper motor neuron lesions is attributed by many clinicians to hyperactive stretch reflexes. The purpose of this study was to examine the passive stretch reflexes of the biceps and brachioradialis muscles in order to assess their possible relative contributions to the flexion posture. Twenty-one patients with upper motor neuron lesions were tested, using an automated system to produce controlled passive movement strech reflexes. Ratios derived from the electromyographic activity elicited during passive movement were used for quantitative comparisons. The stretch reflex response of the brachioradialis muscle was larger and earlier than the biceps response. A surprising finding was reciprocal activity in these two synergists following phasic stretch.

Reflex and voluntary electromyographic activity in patients with hemiparesis.

The purpose of this study was to quantify the effect of combining voluntary effort with passive muscle stretch in the major flexors and extensors of the elbow and knee joints in order to test the validity of the assumption that stretching a muscle in conjunction with voluntary effort enhances the production of muscle activity more than muscle stretch or voluntary effort alone. This was accomplished by using a computer-controlled test instrument to produce the conditions necessary for measuring stretch reflex activity, voluntary effort, and stretch reflex activity plus voluntary effort, and then quantitatively examining the EMG activity associated with each test condition. In general, greater EMG activity was produced by the combination of muscle stretch and voluntary effort than by either muscle stretch or voluntary effort alone. Clinical implications of these findings are discussed.