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Biomedical subjects

Tim L Uhl

Publications and source records attributed to Tim L Uhl.

14 recordsLinked to original sources
PubMed2006

Measurement of lumbar multifidus muscle contraction with rehabilitative ultrasound imaging.

Rehabilitative Ultrasound Imaging (RUSI) has been validated as a noninvasive method to measure activation of selected muscles. The purpose of this study was to determine the relationship between muscle thickness change, as measured by ultrasonography, and electromyography (EMG) activity of the lumbar multifidus (LM) muscle in normal subjects. Bipolar fine wire electrodes were inserted into the LM at the L4 level of five subjects. Simultaneous EMG and RUSI data (muscle thickness) were collected while subjects performed increasingly demanding postural response tasks thought to activate the LM muscle. To determine the relationship between muscle thickness change and EMG activity, the normalized EMG data were correlated to normalized RUSI data. To determine if the tasks increased the demand on the LM, the mean EMG data were compared over each of the four tasks. Muscle thickness change as measured by RUSI was highly correlated with EMG activity of LM in asymptomatic subjects (r=.79,P<.001). Mean EMG data showed increasing levels of activation across tasks (19-34% of maximum voluntary isometric contraction (MVIC)). The results of the repeated measures ANOVA demonstrated theses differences were significant (F(3,12)=25.39,P<.001). Measurement of muscle thickness change utilizing RUSI is a valid and potentially useful method to measure activation of the LM muscle in a narrow range (19-34% of MVIC) in an asymptomatic population.

Adult↗
PubMed2006

Reliability of the three-dimensional pendulum test for able-bodied children and children diagnosed with cerebral palsy.

This prospective study compared the test-retest reliability of thirteen variables calculated from the pendulum test in able-bodied children to those of children diagnosed with cerebral palsy. Ten healthy children and 10 children with a primary diagnosis of cerebral palsy (CP) (mean age 13 years) participated in the study. Data were collected using a three-dimensional motion analysis system on two separate occasions 73+/-28 days apart. The between day reliability ICC scores of all variables were moderate to very high (0.60-0.98) for children with CP and high to very high (0.71-0.98) for able-bodied children. The children with CP demonstrated slower maximum angular velocity compared to the able-bodied children (202 degrees /s versus 293 degrees /s, p<0.01). The time to maximum angular velocity occurred sooner for children with CP compared to able-bodied children (0.22s versus 0.34s, p<0.001). For some children with CP, the knee motions demonstrated were not oscillations of decreasing magnitude. Therefore the integrals of knee motion in each plane were calculated. For both groups of subjects the largest integrals of motion were in the sagittal plane (knee flexion/extension). The able-bodied subject's integrals were twice as large compared to subjects diagnosed with CP (p<0.01). High test-retest reliability of the variables suggests that the pendulum test provides an objective and reliable method to assess quadriceps spasticity in children with cerebral palsy.

Adolescent↗
PubMed2006

EMG analysis of shoulder muscle fatigue during resisted isometric shoulder elevation.

The purpose of this study was to determine if a difference existed in the rate of fatigue of select shoulder muscles during isometric shoulder elevation and if the measured rate of fatigue was consistent from day to day. Shoulder muscle fatigue has been associated with alterations in joint mechanics and possibly contributes to shoulder dysfunction. While research exists, there is limited information on an objective and reliable measure of shoulder fatigue. Sixteen asymptomatic subjects were evaluated. The subjects held a weight equivalent to 60% of his/her Maximum Voluntary Isometric Contraction (MVIC) while elevating in the scapular plane. Surface electrodes were applied to collect electromyographic activity from the upper trapezius, middle deltoid, serratus anterior, and lower trapezius muscles while the arm was held at 90 degrees elevation. Data collection ceased when the subject was no longer able to maintain 90 degrees of elevation. The subject then rested and a second trial performed. One week later, the two-trial procedure was repeated. A significant interaction of trial x day x muscle was found for the rate of fatigue. Post hoc analysis revealed that the rate of fatigue of the middle deltoid was significantly greater than the other muscles tested. The intraday reliability was good for all muscles but interday reliability was poor except for the middle deltoid. This study suggests that the middle deltoid appears to fatigue faster than the other shoulder muscles tested at the selected level of shoulder elevation. This should be considered in designing a rehabilitation program to develop a sequence that does not overly fatigue the middle deltoid.

Adult↗
PubMed2006

A comparison of individual joint contributions to multijoint position reproduction acuity in overhead-throwing athletes.

BACKGROUND: Measures of joint position sense often test single-axis motions isolating a single joint. Such methods hamper our ability to apply findings to functional multijoint activities. Using a functional, active, multijoint test, we measured upper-extremity position reproduction in overhead-throwers. We compared acuity among four joints and examined individual joint contributions or patterns of contribution among joints to overall task acuity. METHODS: We used an electromagnetic tracking device to measure reproduction of two functional upper-extremity positions. We calculated absolute, constant and variable error at four upper-extremity joints around multiple axes of rotation: three axes at the scapulothoracic and glenohumeral joints and two axes at the elbow and wrist. To represent individual joint acuity, we calculated 3-dimensional variable error. Additional 3-dimensional variable error scores using deviation in hand position (with reference to the thorax) represented overall task acuity. We used principle component analyses to identify contributions of individual joints or patterns of contribution among joints to overall task acuity for absolute, constant and variable error. FINDINGS: Scapulothoracic and glenohumeral joints displayed better acuity compared with elbow and wrist joints. When examined separately, absolute, constant and variable error scores did not indicate any individual joint contributed more to task acuity. When we examined the principle components of all error score measures together, a distinct proximal-to-distal pattern of joint contribution to overall task acuity emerged. INTERPRETATION: Proximal joints display better reposition acuity compared with distal joints, however proximal joints contribute more to acuity of the overall task. Our results indicate that upper-extremity joints do not function independently in repositioning tasks and measures of absolute, constant and variable errors combined over multiple joints may better represent upper-extremity function.

Adult↗
PubMed2006

Outcomes of a weight-bearing rehabilitation program for patients diagnosed with patellofemoral pain syndrome.

OBJECTIVE: To determine the effects of a weight-bearing rehabilitation program on quadriceps and gluteus medius electromyographic activity, pain, and function in subjects diagnosed with patellofemoral pain syndrome (PFPS). DESIGN: Pretest and posttest 6-week intervention study. SETTING: Musculoskeletal research laboratory. PARTICIPANTS: Fourteen subjects diagnosed with PFPS and 14 healthy control subjects volunteered to participate in this study. No subjects withdrew from the study because of adverse effects. INTERVENTION: Subjects diagnosed with PFPS participated in a 6-week rehabilitation program. The rehabilitation program consisted of weight-bearing exercises that focused on strengthening the quadriceps and hip abductor musculature. MAIN OUTCOME MEASURES: Electromyographic onsets of the vastus medialis oblique (VMO) and vastus lateralis and onset and duration of the gluteus medius were collected during a stair-stepping task that was performed during the pretest and posttest. A visual analog scale (VAS) and Functional Index Questionnaire (FIQ) were administered at pretest and posttest and each week of the intervention. RESULTS: Vastus lateralis and VMO onset timing differences (vastus lateralis electromyographic onset minus VMO electromyographic onset) and VAS and FIQ scores significantly improved for patients diagnosed with PFPS. Vastus lateralis and VMO onset timing in the PFPS group were significantly different from those in the control group at baseline and were not significantly different from the control group after the intervention. We did not find differences in gluteus medius onsets or duration of activity. CONCLUSIONS: Subjects diagnosed with PFPS responded favorably and quickly to a therapeutic exercise program that incorporated quadriceps and hip musculature strengthening. The efficacy of the therapeutic exercise program used in this study should be further investigated in a larger subject population.

Adolescent↗
PubMed2005

Kinematic and EMG characteristics of simple shoulder movements with proprioception and visual feedback.

The objective of this study was to determine if simple, shoulder movements use the dual control hypothesis strategy, previously demonstrated with elbow movements, and to see if this strategy also applies in the absence of visual feedback. Twenty subjects were seated with their right arm abducted to 90 degrees and externally rotated in the scapular plane. Subjects internally rotated to a target position using a custom shoulder wheel at three different speeds with and without visual feedback. Kinematics were collected with a motion analysis system and electromyographic (EMG) recordings of the pectoralis major (PECT), infraspinatus (INFRA), anterior and posterior (ADELT, PDELT) deltoid muscles were used to evaluate muscle activity patterns during movements. Kinematics changed as movement speed increased with less accuracy (p<0.01). Greater EMG activity was observed in the PECT, PDELT, and INFRA with shorter durations for the ADELT, PDELT and INFRA. Movements with only kinesthetic feedback were less accurate (p<0.01) and performed faster (p<0.01) than movements with visual feedback. EMG activity suggests no major difference in CNS control strategies in movements with and without visual feedback. Greater resolution with visual feedback enables the implementation of a dual control strategy, allowing greater movement velocity while maintaining accuracy.

Adult↗
PubMed2004

Measures of accuracy for active shoulder movements at 3 different speeds with kinesthetic and visual feedback.

STUDY DESIGN: Repeated-measures experiment. OBJECTIVE: To compare measures of end point accuracy (EPA) for 2 feedback conditions: (1) visual and kinesthetic feedback and (2) kinesthetic feedback alone, during shoulder movements, at 3 different speeds. BACKGROUND: Shoulder joint kinesthesia is typically reported with EPA measures, such as constant error. Reporting multiple measures of EPA, such as variable error and absolute error, could provide a more detailed description of performance. METHODS AND MEASURES: Subjects were seated with the shoulder abducted 90 degrees in the scapular plane and externally rotated 75 degrees, with the forearm placed in a custom shoulder wheel. Subjects internally rotated the shoulder 27 degrees to a target position at 48 degrees of shoulder external rotation for both conditions. Motion analysis was used to determine peak angular velocity and 3 EPA measures for shoulder movements. Each EPA measure was compared between the 2 feedback conditions and among the 3 speeds with a separate 2-way analysis of variance. RESULTS: Movements performed with kinesthetic feedback alone, measured by constant error (P<.01), variable error (P<.01), and absolute error (P<.01), were less accurate than movements performed with visual and kinesthetic feedback. Faster movements were less accurate when measured by constant error (P = .01) and absolute error (P<.01) than slower movements. Subjects tended to overshoot the target in the absence of visual feedback; however, movement speed played minimal role in the overshooting. CONCLUSIONS: Multiple measures of EPA, such as constant, variable, and absolute error during simple restricted shoulder movements may provide additional information regarding the evaluation of a motor performance or identify different central nervous system control mechanisms for joint kinesthesia.

Adult↗
PubMed2003

Effects of moist heat on hamstring flexibility and muscle temperature.

The purpose of this study was to determine whether the application of a moist heat pack (MHP) could increase hamstring flexibility. Both legs for each subject were used for this study. Each leg was randomly assigned to either an MHP leg or a control leg condition. Twenty-seven male subjects (height = 178.5 +/- 8.6 cm; weight = 84.4 +/- 18.7 kg; age = 21.9 +/- 6.3 years) volunteered for this study. For the MHP leg condition, baseline hamstring flexibility was measured using an active knee extension test. A 23-ga indwelling thermistor was inserted to a depth of 2.54 cm to measure hamstring temperature. After baseline temperature was recorded, 2 MHPs were placed on either side of the thermistor until temperature was increased by 0.4 degrees C. Hamstring flexibility postintervention measurements were performed at 0, 4, 8, and 16 minutes. The same protocol was used for the control leg, without the MHP application. A 2 x 5 repeated-measures analysis of variance revealed no significant interaction between the MHP and the control leg condition. These results support previous findings that MHP application does not significantly affect muscle flexibility. After application of an MHP, it takes 20-25 minutes to increase intramuscular temperatures by 0.4 degrees C. Both of these findings should be taken into consideration when using an MHP to increase muscle flexibility.

Adolescent↗
PubMed2003

Shoulder musculature activation during upper extremity weight-bearing exercise.

STUDY DESIGN: Repeated-measures design comparing 7 static weight-bearing shoulder exercises. OBJECTIVE: The purpose of this study was to determine the demand on shoulder musculature during weight-bearing exercises and the relationship between increasing weight-bearing posture and shoulder muscle activation. BACKGROUND: Weight-bearing shoulder exercises are commonly prescribed in the rehabilitation of shoulder injuries. Limited information is available as to the demands placed on shoulder musculature while these exercises are performed. METHODS: Eighteen healthy college students volunteered for this study. Surface bipolar electrodes were applied over the infraspinatus, posterior deltoid, anterior deltoid, and pectoralis major muscles. Fine-wire bipolar intramuscular electrodes were inserted into the supraspinatus muscle. Electromyographic (EMG) root mean square signal intensity was normalized to 1 second of EMG obtained with a maximal voluntary isometric contraction (MVIC). Subjects were tested under 7 isometric exercise positions that progressively increased upper extremity weight-bearing posture. RESULTS: There was a high correlation between increasing weight-bearing posture and muscular activity (r = 0.97, P < 0.01). There was relatively little demand on the shoulder musculature for the prayer and quadruped positions (2%-10% MVIC). Muscular activation was greater for the infraspinatus than for other shoulder muscles throughout most of the exercise positions tested. CONCLUSION: These results indicate that alterations of weight-bearing exercises, by varying the amount of arm support and force, resulted in very different demands on the shoulder musculature. Specifically, the infraspinatus was particularly active during the weight-bearing exercises used in this study.

Adult↗
PubMed2002

Clinical assessment and rehabilitation of shoulder and knee sensorimotor control.

The orthopedic surgeon must perform a thorough evaluation of an unstable joint to derive the accurate diagnosis. One component of this examination is evaluation of the sensorimotor system. This article provides an overview of techniques and methodology used to assess the sensorimotor system. Rehabilitation concepts are presented to assist the physician during patient consultation following injury or surgery.

Humans↗
PubMedDate not supplied

Physeal changes and range-of-motion differences in the dominant shoulders of skeletally immature baseball players.

The purpose of this study was to document range-of-motion differences and radiographic changes in the dominant shoulder of skeletally immature throwers and to determine how pain associated with throwing may relate to these changes. Seventy-nine male youth baseball players (aged 8-15 years) completed a questionnaire, a shoulder examination, and a series of radiographs to determine physeal changes and humeral retroversion. Radiographs were reviewed and interpreted by a blinded musculoskeletal radiologist. Measurement of proximal humeral physeal width revealed a significant increase on the dominant side for the entire group, in subjects with a history of symptoms during the current season, and in subjects who had never had symptoms. Visual radiographic changes were commonly found in subjects with a history of pain (16/26 [62%]) as well as in those subjects without symptoms (29/53 [55%]). Subjects had increased external rotation of the dominant arm as compared with the nondominant arm, and this pattern increased in magnitude as the throwers aged. Range-of-motion and radiographic asymmetry of the shoulders is common, is often asymptomatic, and may represent adaptive changes in this population.

Adolescent↗
PubMedDate not supplied

The effect of limb support on muscle activation during shoulder exercises.

The purpose of this study was to determine the difference in demands on glenohumeral musculature during unsupported and supported active range-of-motion (AROM) shoulder exercises. Twenty healthy subjects volunteered for this study. Surface or fine-wire bipolar electrodes were applied to the infraspinatus, posterior deltoid, anterior deltoid, pectoralis major, and supraspinatus muscles. Subjects performed vertical wall slides and diagonal wall slides (45 degrees angle) with their hand in contact with the wall (supported) and not in contact with the wall (unsupported). Significantly greater supraspinatus activity was found in the unsupported exercises versus the supported exercises (F(4,76) = 4.38, P = .003). Exercises performed in the 45 degrees diagonal position were more demanding on shoulder musculature than vertical exercises (F(1,19) = 19.3, P < .001). Although our results were obtained in healthy subjects and the implications in a pathological population are not clear, we suggest that when designing a progression of exercises for increasing shoulder muscular activity, supported short lever arm AROM exercises should precede unsupported long lever arm AROM exercises.

Adult↗
PubMedDate not supplied

Qualitative clinical evaluation of scapular dysfunction: a reliability study.

The purpose of this study was to determine the intrarater and interrater reliability of a clinical evaluation system for scapular dysfunction. No commonly accepted terminology presently exists for describing the abnormal dynamic scapular movement patterns that are commonly associated with shoulder injury. A method of observation was devised for clinical evaluation of scapular dysfunction. Blinded evaluators (2 physicians and 2 physical therapists) were familiarized with the evaluation method of scapular movement patterns before viewing a videotape of 26 subjects with and without scapular dysfunction. Each evaluator was asked to categorize the predominant scapular movement pattern observed during bilateral humeral scaption and abduction motions. Reliability was assessed by a kappa coefficient. Intertester reliability (kappa = 0.4) was found to be slightly lower than intratester reliability (kappa = 0.5). These results indicate that, with refinement, this qualitative evaluation method may allow clinicians to standardize the categorization of dynamic scapular dysfunction patterns.

Adult↗