Gregory Karst | University of Nebraska Medical Center (original) (raw)
Papers by Gregory Karst
![Research paper thumbnail of Multijoint arm movements [microform] : predictions and observations regarding initial muscle activity at the shoulder and elbow /](https://attachments.academia-assets.com/41719450/thumbnails/1.jpg)
](Thesis (Ph. D. - Physiology)--University of Arizona, 1989. Includes bibliographical references (l... more Thesis (Ph. D. - Physiology)--University of Arizona, 1989. Includes bibliographical references (leaves 187-194). Microfiche. s
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Journal of Neurophysiology
1. The question we addressed was the following: what rules does the CNS employ, given the initial... more 1. The question we addressed was the following: what rules does the CNS employ, given the initial and final positions of the arm for a pointing movement, to decide which shoulder and elbow muscles ("agonists") to activate for initiating movement? 2. Widely varying initial and final positions were used, so that the movements studied encompassed much of the reachable work space within the horizontal plane. For each movement, the initial electromyographic (EMG) activity at each joint was classified qualitatively in terms of the "sign," i.e., flexor or extensor muscle activity, and quantitatively in terms of the integral of the rectified EMG. 3. The sign of initial muscle activity at each joint was found to be related to the angular excursions at both joints during movement to the final position. 4. Two different hypothesized rules, derived from previously proposed strategies for control of multijoint limb movements, were tested for their ability to predict correctly...
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In order to manipulate objects with our hands, we routinely use coordinated rotations about the s... more In order to manipulate objects with our hands, we routinely use coordinated rotations about the shoulder and elbow to convey the hand from point to point within the surrounding workspace. The seeming ease with which the nervous system is able to generate muscle activation patterns appropriate for pushing an elevator button or reaching for the telephone appear to belie the well-documented complexity of the mechanics underlying such movements. In order to delineate rules by which the CNS might choose suitable patterns of muscle activation, and to identify the movement parameters most important in implementing those rules, we have investigated the electromyographic (EMG) activity of shoulder and elbow muscles associated with a variety of two-joint pointing movements in the horizontal plane (Hasan and Karst, 1989; Karst, 1989).
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Thesis (M.S. - Animal Physiology)--University of Arizona, 1984. Includes bibliographical referenc... more Thesis (M.S. - Animal Physiology)--University of Arizona, 1984. Includes bibliographical references (leaves 53-58). Microfiche. s
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Aviation Space and Environmental Medicine
Ventilation (VE), CO2 output (VCO2), oxygen uptake (VO2), respiratory exchange ratio (R), and the... more Ventilation (VE), CO2 output (VCO2), oxygen uptake (VO2), respiratory exchange ratio (R), and the ventilatory equivalents for VO2 and VCO2 were measured during graded exercise before and after 10 d of continuous bed rest (BR) in the -6 degrees head-down position to determine the effect of deconditioning on the anaerobic threshold (AT), i.e., the highest workrate or VO2 which was achieved without evidence of lactic acidosis, as judged from the profile of ventilatory and gas exchange responses. Ten healthy male subjects performed a supine graded cycle ergometer test before (pre) and after (post) BR which consisted of 4 min of unloaded pedaling at 60 rpm followed by an increased workrate of 15 W X min-1 until volitional fatigue (max). VE, VCO2, VO2, R, VE/VO2 and VE/VCO2 were measured every 30 s and used collectively to identify the AT. Plasma (PV) and blood (BV) volumes were measured pre- and post-BR by T-1824. Following BR, VO2max decreased from 2.42 +/- 0.17 to 2.25 +/- 0.13 L X min...
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Journal of applied biomechanics, 2012
The purpose of this investigation was to evaluate the effect of a lower body positive pressure su... more The purpose of this investigation was to evaluate the effect of a lower body positive pressure support system on the joint kinematics and activity of the lower extremity antigravity musculature of adults and children during walking. Adults (age = 25 ± 4 years) and children (age = 13 ± 2 years) walked at a preferred speed and a speed that was based on the Froude number, while 0-80% of their body weight was supported. Electrogoniometers were used to monitor knee and ankle joint kinematics. Surface electromyography was used to quantify the magnitude of the vastus lateralis and gastrocnemius muscle activity. There were three key findings: (1) The lower extremity joint angles and activity of the lower extremity antigravity muscles of children did not differ from those of adults. (2) The magnitude of the changes in the lower extremity joint motion and antigravity muscle activity was dependent upon an interaction between body weight support and walking speed. (3) Lower body positive pressu...
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The Journal of physiology, 1990
1. The purpose of this study was to investigate tetanic force development and relaxation in singl... more 1. The purpose of this study was to investigate tetanic force development and relaxation in single motor units that were subjected to a standard fatigue test. 2. Motor units of tibialis posterior, a hindlimb muscle in the adult cat, were assigned to four categories (i.e. types S, FR, FI, FF) using conventional criteria. 3. Based on the first tetanus of the fatigue test, type S units took significantly longer to develop force and to relax than the fast-twitch units. Within the fast-twitch subpopulations, type FR and FI units were significantly slower to develop force and to relax than were type FF units, but there were no significant differences between type FR and FI units. 4. After 120 s of the fatigue test, the rates of force development were faster than initial values in type S and FR units, but were largely unchanged for the type FI and FF units. Most relaxation parameters were unaffected by stimulation in type S and FR units, but all parameters became significantly slower in ty...
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Medicine & Science in Sports & Exercise, 1984
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Journal of Geriatric Physical Therapy, 2012
Persons with total knee arthroplasty (TKA) have many impairments that may compromise postural con... more Persons with total knee arthroplasty (TKA) have many impairments that may compromise postural control. Most work examining postural control following TKA has focused on static and reactive postural control. The purpose of this study was to (1) compare anticipatory postural adjustments (APAs) between individuals with TKA and healthy controls; and (2) identify possible pre- to postoperative changes in APAs in those undergoing TKA. Ten individuals planning TKA and 10 healthy age- and sex-matched controls were recruited. During a standing reaching task, lower extremity muscle activity was measured using electromyography (EMG) onsets and normalized EMG amplitudes, and center of pressure (COP) excursion was measured via a force platform. Other outcome measures included isometric strength of the knee flexors and extensors. Individuals in the TKA group were tested preoperatively, and at 3 and 6 months postoperatively. Controls were also measured 3 times over 6 months. There were no pre- to postoperative differences in lower extremity EMG onsets, normalized EMG amplitudes, or COP excursion in those with TKA. When compared to controls, individuals with TKA demonstrated lower EMG amplitudes of the vastus lateralis and biceps femoris, whereas EMG onsets and COP excursion did not differ. Individuals with TKA demonstrated lower knee extension torque. It seems that the surgery itself did not alter APAs among individuals with TKA. Potential contributors to the differences in EMG amplitudes in those with TKA compared to controls, such as impaired neural activation or efforts to reduce stress on the involved knee joint, need further investigation.
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Journal of Neurologic Physical Therapy, 2004
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Perceptual and Motor Skills, 2012
The kinematics of children&#3... more The kinematics of children's walking are nearly adult-like by about age 3-4 years, but metabolic efficiency of walking does not reach adult values until late in adolescence or early adulthood, perhaps due to higher coactivation of agonist/antagonist muscle pairs in adolescents. Additionally, it is unknown how use of a body weight-supported treadmill device affects coactivation, but because unloading will alter the activity of anti-gravity muscles, it was hypothesized that muscle coactivation will be altered as well. Muscle coactivation during treadmill walking was evaluated for adolescents (ages 10 to 17 years, M = 13.2, SD = 2.2) and adults (ages 22 to 35 years, M = 25.2, SD = 4.3), for thigh muscles (vastus lateralis/biceps femoris) and lower leg muscles (tibialis anterior/gastrocnemius). Conditions included body weight unloadings from nearly 0% to 80% of body weight, while walking at a preferred speed (self-selected, overground speed) or a reduced speed. Unloading was accomplished using a lower body positive pressure support system. Coactivation was found to be higher in adolescents than in adults, but only for the lower leg muscles.
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Physical Therapy
Inappropriate neural control of the quadriceps femoris muscle group has been implicated in patell... more Inappropriate neural control of the quadriceps femoris muscle group has been implicated in patellofemoral pain syndrome (PFPS). This study investigated the timing of initial electromyographic (EMG) activity of the vastus medialis oblique muscle (VMO) and the vastus lateralis muscle (VL) in asymptomatic subjects and subjects with PFPS during reflex and voluntary muscle activity. Fifteen symptomatic subjects (SYMP group) (9 with bilateral symptoms) and 12 asymptomatic subjects (ASYMP group) participated. Both knees were tested in the ASYMP group and only the symptomatic knees were tested in the SYMP group, resulting in a total of 24 data sets from each group. Electromyographic data were recorded from the VMO and VL under three conditions: reflex knee extension (RFLX) elicited by a patellar tendon tap, and active knee extension in non-weight-bearing (NWB) and weight-bearing (WB) situations. For each condition, EMG activity onset times for the VMO and VL were determined from ensemble av...
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Physical Therapy
The purpose of this study was to determine whether active exercises combining hip adduction with ... more The purpose of this study was to determine whether active exercises combining hip adduction with knee extension activate medial components of the quadriceps femoris muscle (QF) more than does knee extension alone. Twelve healthy adults (6 men, 6 women), aged 20 to 36 years (mean = 24.8, SD = 5.8), participated in the study. The subjects performed quadriceps femoris setting (QS), straight leg raising (SLR), straight leg raising with the hip laterally rotated (SLR/LR), and straight leg raising combined with isometric hip adduction (SLR/ADD). Electromyographic (EMG) activity was recorded from the oblique (VMO) and longitudinal (VML) portions of the vastus medialis, vastus lateralis (VL), and rectus femoris muscles. Comparison of normalized mean EMG magnitudes revealed that the single-joint QF components (VMO, VML, and VL) demonstrated significantly greater activity during QS than during any of the three SLR variations and that SLR/LR and SLR/ADD did not elicit greater relative activity...
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Journal of Orthopaedic & Sports Physical Therapy, 1996
Various authors have indicated that imbalance of the vastus medialis/vastus lateralis muscles mig... more Various authors have indicated that imbalance of the vastus medialis/vastus lateralis muscles might lead to patellofemoral pain syndrome. However, few reports have been published to substantiate such a hypothesis. The purpose of this study was to attempt to set a scale for the normal reflex response times of the vastus medialis oblique and vastus lateralis muscles after a patellar tendon tap and to determine if patellofemoral pain syndrome patients have an alteration in this firing sequence. A control group of 80 healthy adults was compared with a group of 19 patellofemoral pain syndrome patients. Results indicated that the reflex response time of the vastus medialis oblique was significantly shorter than the reflex response time of the vastus lateralis in the normal subjects (p < or = .01). When comparing these data in the patellofemoral pain syndrome group, a significant earlier firing was obtained from the vastus lateralis in comparison with the vastus medialis oblique (p < or = .01). These findings suggest that a reversal has occurred in the firing pattern of the vastus medialis oblique and vastus lateralis muscles in patellofemoral pain syndrome patients. The results indicate an alteration in the neuromuscular answer of the vastus medialis oblique and vastus lateralis muscles during a patellar tendon tap.
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Journal of Orthopaedic & Sports Physical Therapy, 1997
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Physical therapy, 1998
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The Journals of Gerontology Series A: Biological Sciences and Medical Sciences, 1999
Impaired control of foot trajectory during the swing phase of gait is hypothesized to increase th... more Impaired control of foot trajectory during the swing phase of gait is hypothesized to increase the risk of slipping or tripping. Before assessing the predictive validity of foot trajectory measures with respect to incidence of falls, it is necessary to establish their reliability. The purpose of this study is to assess within- and between-session reliability of foot trajectory measures and traditional temporal-distance measures in healthy elderly women during gait. Sixteen healthy, elderly women (ages 65-79 years) completed six sets of five trials each of natural and fast cadence gait during a 3.5-hour period on each of 4 days. An optoelectric motion analysis system and heel switches were used to obtain both foot trajectory (minimum toe clearance during swing, vertical, and horizontal heel contact velocities) and temporal-distance measures (step width, cadence, velocity, stride length, and time). Within-session test-retest reliability of all variables at natural and fast speeds was good to excellent, with intraclass correlation coefficients (ICCs) of greater than 0.9 for all but one measure (fast cadence stride time). ICCs for between-session test-retest reliability were slightly lower, but still greater than 0.9 for all but two measures (fast cadence stride time and natural cadence vertical heel contact velocity). Heel contact velocities quantified at the instant of heel contact correlated strongly with values obtained by averaging over the last 2% of the gait cycle. The good to excellent within- and between-session reliability of these foot trajectory measures supports their use as a possible means of assessing subtle changes in gait motor control. Confirmation of an association between alterations in foot trajectory measures and incidence of falls awaits further study.
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Pediatric Physical Therapy, 1998
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Journal of Orthopaedic & Sports Physical Therapy, 2004
A repeated-measures, counterbalanced design. To test whether subjects could learn and retain the ... more A repeated-measures, counterbalanced design. To test whether subjects could learn and retain the ability to alter the relative activity of abdominal muscle groups when performing trunk curl exercises. Although trunk curl exercises are widely prescribed, a disadvantage of trunk curls is that they primarily activate rectus abdominis, while the internal and external oblique abdominis muscles are considered to be more important contributors to lumbar stability. A convenience sample of 25 subjects performed trunk curl exercises in accordance with 3 different sets of instructions: nonspecific instructions (NS), instructions intended to emphasize rectus abdominis activity (RE), and instructions intended to emphasize oblique abdominis activity (OE). Electromyographic (EMG) activity was recorded from the upper and lower rectus and the internal and external oblique abdominis muscles while a physical target was used to insure that the trunk was raised to the same height for all conditions. Normalized root-mean-square EMG amplitude measures were used to test for instruction-dependent changes in the relative EMG activity of the rectus and oblique muscle groups. Following a single, brief, instruction session, subjects performing trunk curls had significantly greater normalized oblique:rectus EMG ratios when following OE instructions (mean [+/- SD] oblique-rectus ratio, 1.45 +/- 0.34) than when following RE (mean [+/- SD] oblique-rectus ratio, 0.76 +/- 0.24) or NS (mean [ISD] oblique-rectus ratio, 0.63 +/- 0.23) instructions. Retesting 1 week later indicated that subjects retained this skill. With minimal instruction, subjects are able to volitionally alter the relative activity of the oblique and rectus abdominis muscles when performing trunk curls. Incorporating instructions emphasizing oblique abdominis activity into lumbar stabilization programs appears promising and has potential advantages over other approaches to altering abdominal muscle activity during trunk
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Archives of Physical Medicine and Rehabilitation, 1995
The objective of this article was to determine, using selected computerized gait analysis procedu... more The objective of this article was to determine, using selected computerized gait analysis procedures, whether variation exists in the gait patterns of children with cerebral palsy who exhibit genu recurvatum. This descriptive study compared differences in kinematic, temporal-distance, and electromyographic (EMG) variables between two groups of children with cerebral palsy who exhibited genu recurvatum and age-matched controls. The setting was a motion analysis laboratory. Six children with cerebral palsy who showed genu recurvatum and a control group of four normal children participated in this study. Main outcome measures were hip-knee angle-angle diagrams, knee phase plane plots, knee angle versus time diagrams, stride length, cadence, single-limb support, and EMG data. Through use of hip-knee angle-angle diagrams, knee phase plane plots, and knee angle versus time diagrams, distinctive kinematic patterns emerged, allowing for grouping of subjects. Kinematic measures of knee angle at foot-floor contact and knee angle at greatest extension provided further support for the groups created, as did temporal-distance measures of stride length, cadence, and single-limb support. Analysis of variance procedures for the EMG data showed selected time points in the gait cycle during which differences between the groups were observed. Because differences in kinematic, temporal-distance, and EMG variables existed in this study to warrant grouping into two categories, physical therapists and orthopedic surgeons may need to vary the treatments they introduce dependent on the nature of the child's gait pattern.
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Thesis (Ph. D. - Physiology)--University of Arizona, 1989. Includes bibliographical references (l... more Thesis (Ph. D. - Physiology)--University of Arizona, 1989. Includes bibliographical references (leaves 187-194). Microfiche. s
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Journal of Neurophysiology
1. The question we addressed was the following: what rules does the CNS employ, given the initial... more 1. The question we addressed was the following: what rules does the CNS employ, given the initial and final positions of the arm for a pointing movement, to decide which shoulder and elbow muscles ("agonists") to activate for initiating movement? 2. Widely varying initial and final positions were used, so that the movements studied encompassed much of the reachable work space within the horizontal plane. For each movement, the initial electromyographic (EMG) activity at each joint was classified qualitatively in terms of the "sign," i.e., flexor or extensor muscle activity, and quantitatively in terms of the integral of the rectified EMG. 3. The sign of initial muscle activity at each joint was found to be related to the angular excursions at both joints during movement to the final position. 4. Two different hypothesized rules, derived from previously proposed strategies for control of multijoint limb movements, were tested for their ability to predict correctly...
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In order to manipulate objects with our hands, we routinely use coordinated rotations about the s... more In order to manipulate objects with our hands, we routinely use coordinated rotations about the shoulder and elbow to convey the hand from point to point within the surrounding workspace. The seeming ease with which the nervous system is able to generate muscle activation patterns appropriate for pushing an elevator button or reaching for the telephone appear to belie the well-documented complexity of the mechanics underlying such movements. In order to delineate rules by which the CNS might choose suitable patterns of muscle activation, and to identify the movement parameters most important in implementing those rules, we have investigated the electromyographic (EMG) activity of shoulder and elbow muscles associated with a variety of two-joint pointing movements in the horizontal plane (Hasan and Karst, 1989; Karst, 1989).
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Thesis (M.S. - Animal Physiology)--University of Arizona, 1984. Includes bibliographical referenc... more Thesis (M.S. - Animal Physiology)--University of Arizona, 1984. Includes bibliographical references (leaves 53-58). Microfiche. s
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Aviation Space and Environmental Medicine
Ventilation (VE), CO2 output (VCO2), oxygen uptake (VO2), respiratory exchange ratio (R), and the... more Ventilation (VE), CO2 output (VCO2), oxygen uptake (VO2), respiratory exchange ratio (R), and the ventilatory equivalents for VO2 and VCO2 were measured during graded exercise before and after 10 d of continuous bed rest (BR) in the -6 degrees head-down position to determine the effect of deconditioning on the anaerobic threshold (AT), i.e., the highest workrate or VO2 which was achieved without evidence of lactic acidosis, as judged from the profile of ventilatory and gas exchange responses. Ten healthy male subjects performed a supine graded cycle ergometer test before (pre) and after (post) BR which consisted of 4 min of unloaded pedaling at 60 rpm followed by an increased workrate of 15 W X min-1 until volitional fatigue (max). VE, VCO2, VO2, R, VE/VO2 and VE/VCO2 were measured every 30 s and used collectively to identify the AT. Plasma (PV) and blood (BV) volumes were measured pre- and post-BR by T-1824. Following BR, VO2max decreased from 2.42 +/- 0.17 to 2.25 +/- 0.13 L X min...
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Journal of applied biomechanics, 2012
The purpose of this investigation was to evaluate the effect of a lower body positive pressure su... more The purpose of this investigation was to evaluate the effect of a lower body positive pressure support system on the joint kinematics and activity of the lower extremity antigravity musculature of adults and children during walking. Adults (age = 25 ± 4 years) and children (age = 13 ± 2 years) walked at a preferred speed and a speed that was based on the Froude number, while 0-80% of their body weight was supported. Electrogoniometers were used to monitor knee and ankle joint kinematics. Surface electromyography was used to quantify the magnitude of the vastus lateralis and gastrocnemius muscle activity. There were three key findings: (1) The lower extremity joint angles and activity of the lower extremity antigravity muscles of children did not differ from those of adults. (2) The magnitude of the changes in the lower extremity joint motion and antigravity muscle activity was dependent upon an interaction between body weight support and walking speed. (3) Lower body positive pressu...
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The Journal of physiology, 1990
1. The purpose of this study was to investigate tetanic force development and relaxation in singl... more 1. The purpose of this study was to investigate tetanic force development and relaxation in single motor units that were subjected to a standard fatigue test. 2. Motor units of tibialis posterior, a hindlimb muscle in the adult cat, were assigned to four categories (i.e. types S, FR, FI, FF) using conventional criteria. 3. Based on the first tetanus of the fatigue test, type S units took significantly longer to develop force and to relax than the fast-twitch units. Within the fast-twitch subpopulations, type FR and FI units were significantly slower to develop force and to relax than were type FF units, but there were no significant differences between type FR and FI units. 4. After 120 s of the fatigue test, the rates of force development were faster than initial values in type S and FR units, but were largely unchanged for the type FI and FF units. Most relaxation parameters were unaffected by stimulation in type S and FR units, but all parameters became significantly slower in ty...
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Medicine & Science in Sports & Exercise, 1984
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Journal of Geriatric Physical Therapy, 2012
Persons with total knee arthroplasty (TKA) have many impairments that may compromise postural con... more Persons with total knee arthroplasty (TKA) have many impairments that may compromise postural control. Most work examining postural control following TKA has focused on static and reactive postural control. The purpose of this study was to (1) compare anticipatory postural adjustments (APAs) between individuals with TKA and healthy controls; and (2) identify possible pre- to postoperative changes in APAs in those undergoing TKA. Ten individuals planning TKA and 10 healthy age- and sex-matched controls were recruited. During a standing reaching task, lower extremity muscle activity was measured using electromyography (EMG) onsets and normalized EMG amplitudes, and center of pressure (COP) excursion was measured via a force platform. Other outcome measures included isometric strength of the knee flexors and extensors. Individuals in the TKA group were tested preoperatively, and at 3 and 6 months postoperatively. Controls were also measured 3 times over 6 months. There were no pre- to postoperative differences in lower extremity EMG onsets, normalized EMG amplitudes, or COP excursion in those with TKA. When compared to controls, individuals with TKA demonstrated lower EMG amplitudes of the vastus lateralis and biceps femoris, whereas EMG onsets and COP excursion did not differ. Individuals with TKA demonstrated lower knee extension torque. It seems that the surgery itself did not alter APAs among individuals with TKA. Potential contributors to the differences in EMG amplitudes in those with TKA compared to controls, such as impaired neural activation or efforts to reduce stress on the involved knee joint, need further investigation.
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Journal of Neurologic Physical Therapy, 2004
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Perceptual and Motor Skills, 2012
The kinematics of children&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#3... more The kinematics of children&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s walking are nearly adult-like by about age 3-4 years, but metabolic efficiency of walking does not reach adult values until late in adolescence or early adulthood, perhaps due to higher coactivation of agonist/antagonist muscle pairs in adolescents. Additionally, it is unknown how use of a body weight-supported treadmill device affects coactivation, but because unloading will alter the activity of anti-gravity muscles, it was hypothesized that muscle coactivation will be altered as well. Muscle coactivation during treadmill walking was evaluated for adolescents (ages 10 to 17 years, M = 13.2, SD = 2.2) and adults (ages 22 to 35 years, M = 25.2, SD = 4.3), for thigh muscles (vastus lateralis/biceps femoris) and lower leg muscles (tibialis anterior/gastrocnemius). Conditions included body weight unloadings from nearly 0% to 80% of body weight, while walking at a preferred speed (self-selected, overground speed) or a reduced speed. Unloading was accomplished using a lower body positive pressure support system. Coactivation was found to be higher in adolescents than in adults, but only for the lower leg muscles.
Bookmarks Related papers MentionsView impact
Physical Therapy
Inappropriate neural control of the quadriceps femoris muscle group has been implicated in patell... more Inappropriate neural control of the quadriceps femoris muscle group has been implicated in patellofemoral pain syndrome (PFPS). This study investigated the timing of initial electromyographic (EMG) activity of the vastus medialis oblique muscle (VMO) and the vastus lateralis muscle (VL) in asymptomatic subjects and subjects with PFPS during reflex and voluntary muscle activity. Fifteen symptomatic subjects (SYMP group) (9 with bilateral symptoms) and 12 asymptomatic subjects (ASYMP group) participated. Both knees were tested in the ASYMP group and only the symptomatic knees were tested in the SYMP group, resulting in a total of 24 data sets from each group. Electromyographic data were recorded from the VMO and VL under three conditions: reflex knee extension (RFLX) elicited by a patellar tendon tap, and active knee extension in non-weight-bearing (NWB) and weight-bearing (WB) situations. For each condition, EMG activity onset times for the VMO and VL were determined from ensemble av...
Bookmarks Related papers MentionsView impact
Physical Therapy
The purpose of this study was to determine whether active exercises combining hip adduction with ... more The purpose of this study was to determine whether active exercises combining hip adduction with knee extension activate medial components of the quadriceps femoris muscle (QF) more than does knee extension alone. Twelve healthy adults (6 men, 6 women), aged 20 to 36 years (mean = 24.8, SD = 5.8), participated in the study. The subjects performed quadriceps femoris setting (QS), straight leg raising (SLR), straight leg raising with the hip laterally rotated (SLR/LR), and straight leg raising combined with isometric hip adduction (SLR/ADD). Electromyographic (EMG) activity was recorded from the oblique (VMO) and longitudinal (VML) portions of the vastus medialis, vastus lateralis (VL), and rectus femoris muscles. Comparison of normalized mean EMG magnitudes revealed that the single-joint QF components (VMO, VML, and VL) demonstrated significantly greater activity during QS than during any of the three SLR variations and that SLR/LR and SLR/ADD did not elicit greater relative activity...
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Journal of Orthopaedic & Sports Physical Therapy, 1996
Various authors have indicated that imbalance of the vastus medialis/vastus lateralis muscles mig... more Various authors have indicated that imbalance of the vastus medialis/vastus lateralis muscles might lead to patellofemoral pain syndrome. However, few reports have been published to substantiate such a hypothesis. The purpose of this study was to attempt to set a scale for the normal reflex response times of the vastus medialis oblique and vastus lateralis muscles after a patellar tendon tap and to determine if patellofemoral pain syndrome patients have an alteration in this firing sequence. A control group of 80 healthy adults was compared with a group of 19 patellofemoral pain syndrome patients. Results indicated that the reflex response time of the vastus medialis oblique was significantly shorter than the reflex response time of the vastus lateralis in the normal subjects (p < or = .01). When comparing these data in the patellofemoral pain syndrome group, a significant earlier firing was obtained from the vastus lateralis in comparison with the vastus medialis oblique (p < or = .01). These findings suggest that a reversal has occurred in the firing pattern of the vastus medialis oblique and vastus lateralis muscles in patellofemoral pain syndrome patients. The results indicate an alteration in the neuromuscular answer of the vastus medialis oblique and vastus lateralis muscles during a patellar tendon tap.
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Journal of Orthopaedic & Sports Physical Therapy, 1997
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Physical therapy, 1998
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The Journals of Gerontology Series A: Biological Sciences and Medical Sciences, 1999
Impaired control of foot trajectory during the swing phase of gait is hypothesized to increase th... more Impaired control of foot trajectory during the swing phase of gait is hypothesized to increase the risk of slipping or tripping. Before assessing the predictive validity of foot trajectory measures with respect to incidence of falls, it is necessary to establish their reliability. The purpose of this study is to assess within- and between-session reliability of foot trajectory measures and traditional temporal-distance measures in healthy elderly women during gait. Sixteen healthy, elderly women (ages 65-79 years) completed six sets of five trials each of natural and fast cadence gait during a 3.5-hour period on each of 4 days. An optoelectric motion analysis system and heel switches were used to obtain both foot trajectory (minimum toe clearance during swing, vertical, and horizontal heel contact velocities) and temporal-distance measures (step width, cadence, velocity, stride length, and time). Within-session test-retest reliability of all variables at natural and fast speeds was good to excellent, with intraclass correlation coefficients (ICCs) of greater than 0.9 for all but one measure (fast cadence stride time). ICCs for between-session test-retest reliability were slightly lower, but still greater than 0.9 for all but two measures (fast cadence stride time and natural cadence vertical heel contact velocity). Heel contact velocities quantified at the instant of heel contact correlated strongly with values obtained by averaging over the last 2% of the gait cycle. The good to excellent within- and between-session reliability of these foot trajectory measures supports their use as a possible means of assessing subtle changes in gait motor control. Confirmation of an association between alterations in foot trajectory measures and incidence of falls awaits further study.
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Pediatric Physical Therapy, 1998
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Journal of Orthopaedic & Sports Physical Therapy, 2004
A repeated-measures, counterbalanced design. To test whether subjects could learn and retain the ... more A repeated-measures, counterbalanced design. To test whether subjects could learn and retain the ability to alter the relative activity of abdominal muscle groups when performing trunk curl exercises. Although trunk curl exercises are widely prescribed, a disadvantage of trunk curls is that they primarily activate rectus abdominis, while the internal and external oblique abdominis muscles are considered to be more important contributors to lumbar stability. A convenience sample of 25 subjects performed trunk curl exercises in accordance with 3 different sets of instructions: nonspecific instructions (NS), instructions intended to emphasize rectus abdominis activity (RE), and instructions intended to emphasize oblique abdominis activity (OE). Electromyographic (EMG) activity was recorded from the upper and lower rectus and the internal and external oblique abdominis muscles while a physical target was used to insure that the trunk was raised to the same height for all conditions. Normalized root-mean-square EMG amplitude measures were used to test for instruction-dependent changes in the relative EMG activity of the rectus and oblique muscle groups. Following a single, brief, instruction session, subjects performing trunk curls had significantly greater normalized oblique:rectus EMG ratios when following OE instructions (mean [+/- SD] oblique-rectus ratio, 1.45 +/- 0.34) than when following RE (mean [+/- SD] oblique-rectus ratio, 0.76 +/- 0.24) or NS (mean [ISD] oblique-rectus ratio, 0.63 +/- 0.23) instructions. Retesting 1 week later indicated that subjects retained this skill. With minimal instruction, subjects are able to volitionally alter the relative activity of the oblique and rectus abdominis muscles when performing trunk curls. Incorporating instructions emphasizing oblique abdominis activity into lumbar stabilization programs appears promising and has potential advantages over other approaches to altering abdominal muscle activity during trunk
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Archives of Physical Medicine and Rehabilitation, 1995
The objective of this article was to determine, using selected computerized gait analysis procedu... more The objective of this article was to determine, using selected computerized gait analysis procedures, whether variation exists in the gait patterns of children with cerebral palsy who exhibit genu recurvatum. This descriptive study compared differences in kinematic, temporal-distance, and electromyographic (EMG) variables between two groups of children with cerebral palsy who exhibited genu recurvatum and age-matched controls. The setting was a motion analysis laboratory. Six children with cerebral palsy who showed genu recurvatum and a control group of four normal children participated in this study. Main outcome measures were hip-knee angle-angle diagrams, knee phase plane plots, knee angle versus time diagrams, stride length, cadence, single-limb support, and EMG data. Through use of hip-knee angle-angle diagrams, knee phase plane plots, and knee angle versus time diagrams, distinctive kinematic patterns emerged, allowing for grouping of subjects. Kinematic measures of knee angle at foot-floor contact and knee angle at greatest extension provided further support for the groups created, as did temporal-distance measures of stride length, cadence, and single-limb support. Analysis of variance procedures for the EMG data showed selected time points in the gait cycle during which differences between the groups were observed. Because differences in kinematic, temporal-distance, and EMG variables existed in this study to warrant grouping into two categories, physical therapists and orthopedic surgeons may need to vary the treatments they introduce dependent on the nature of the child's gait pattern.
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