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Biomedical subjects

L R Osternig

Publications and source records attributed to L R Osternig.

At least 19 recordsLinked to original sources
PubMed2005

Attentional deficits in concussion.

PRIMARY OBJECTIVE: The purpose of the present study was to examine deficits in the alerting, orienting and executive components of attention in individuals who have recently suffered a concussion. RESEARCH DESIGN: A group design was used in which the performance by individuals with concussion was compared to control subjects matched for age, height, weight and activity level. METHODS AND PROCEDURES: Participants completed the Attentional Network Test (ANT) that breaks down attention into alerting, orienting and executive components. Reaction time and response accuracy were the dependent variables. MAIN OUTCOMES AND RESULTS: It was found that only the orienting and executive components of attention were affected by concussion, whereas the alerting component was normal. Furthermore, participants with concussion required a significantly longer time than controls to initiate correct responses. CONCLUSIONS: These results suggest that the orienting and executive components of attention are most susceptible to the effects of concussion.

Adolescent↗
PubMed2001

Effects of position and speed on joint torques and knee shear after ACL injury.

PURPOSE: The purpose of this study was to assess the effect of joint position and movement speed on hip (HT) and knee (KT) extensor torque, HT/KT ratio (HKR), and anterior tibial shear (S) in presurgical-ACL deficient (PRE; N = 15), post-ACL reconstructed (POST; N = 15), and uninjured controls (CON; N = 15). METHODS: Measurements were recorded on a semirecumbent variable resistance, closed-chain dynamometer. Tests were conducted at 1 and 1.5 Hz and maximum speed at 33% and 50% 1RM. HT, KT, and S were recorded during the extension phase of the cycle (85 degrees -25 degrees of knee flexion). RESULTS: KT was greatest when the knee was more flexed, whereas HT dominated when it was more extended. This suggests that the hamstrings, as a component of the hip extensors, may generate considerable propulsive force during knee extension, which may help counter anterior tibial shear. S increased whereas KT decreased, suggesting that the quadriceps continue to generate shear force despite the decreasing mechanical advantage producing KT. Increasing knee extension speed significantly decreased S in the POST and CON groups. The correlations between KT and S changed from significantly negative to significantly positive as the knee extended from 85 degrees to 25 degrees in the POST and CON groups. This may be related to the orientation of the patellar tendon, relative to the tibial longitudinal axis that shifts from a posterior to anterior direction, as the knee extends. CONCLUSIONS: Joint position and movement speeds affect the magnitude of hip and knee torques and anterior tibial shear. Reducing the magnitude of S during heavy loads may be a normal phenomenon, and POST surgical subjects may retain or regain this function by 1 yr after surgery.

Adult↗
PubMed2000

Human hip and knee torque accommodations to anterior cruciate ligament dysfunction.

It has been postulated that the adaptations of lower extremity function exhibited by anterior cruciate ligament (ACL) deficient and post-ACL surgical patients represent early accommodations to the loss of ACL function after injury so that excessive anterior displacement of the tibia is prevented. Prior studies have suggested that compensation patterns in ACL deficient and post-ACL surgical subjects may affect joint moments of the knee as well as the hip. However, the variance in knee and hip forces between ACL deficient, post-surgical ACL and uninjured groups has not been clearly elucidated. The purpose of this study was to assess hip:knee extensor torque ratios relative to anterior tibia shear in pre-surgical-ACL deficient, post-surgical and uninjured subjects. Measurements of hip and knee joint moments and anterior tibia shear were recorded from 45 injured and uninjured subjects (21 men, 24 women) during lower extremity, variable resistance exercise. Anterior tibia shear was computed by decomposing joint moments and reaction forces according to a model derived from cadaver knee dissections and radiography, in combination, to estimate the tibio-femoral compressive and shear forces generated by the patellar tendon at various angles throughout the knee joint range. Three groups of subjects were studied: recently injured ACL deficient pre-surgical subjects who were scheduled for immediate surgery (PRE; n = 15); postsurgical subjects who had undergone ACL reconstructive surgery at least 1 year prior to testing (POST; n = 15); and uninjured controls (CON; n = 15). All PRE and POST subjects had a normal contralateral limb. Tests were conducted under six conditions: 1 and 1.5 Hz cadence and maximal speed at 33% and 50% one repetition maximum resistance. The results revealed that the hip:knee ratios were significantly greater for the post-ACL surgical group than the PRE and CON groups (P<0.01; P<0.03). There were significant negative correlations between the hip extensor:knee extensor torque ratios and maximal anterior tibia shear across all groups. The hip:knee extensor torque ratio increased with decreased anterior tibia shear in all groups with significant correlations ranging from -0.55 to -0.88 (P<0.01) for the injured limbs of PRE and POST groups, and -0.64 to -0.78; (P<0.01) for the CON group. The highest overall correlations were found for the post-surgical subjects. The results revealed that anterior tibia shear declined significantly with speed (P<0.01) in all groups. However, the converse was true for the hip:knee extensor torque ratio across speeds. The ratio increased significantly with speed (P<0.001) for all groups at the 33% and 50% resistances. The results suggest (1) that post-ACL surgical subjects appear to accommodate to ACL substitution by using hip extensors to a significantly greater extent than the uninjured controls in closed-chain lower extremity exercise; (2) that the hip:knee extensor torque ratio is significantly related to the magnitude of anterior tibia shear; and (3) that the anterior tibia shear is significantly reduced as speed increases in closed-chain lower extremity exercise.

Adaptation, Physiological↗
PubMed1999

Effects of movement speed and joint position on knee flexor torque in healthy and post-surgical subjects.

Coactivation of knee flexors during knee extension assists in joint stability by exerting an opposing torque to the anterior tibial displacement induced by the quadriceps. This opposing torque is believed to be generated by eccentric muscle actions that stiffen the knee, thereby attenuating strain to joint ligaments, particularly the anterior cruciate ligament (ACL). However, as the lengths of knee muscles vary with changes in joint position, the magnitude of flexor/extensor muscle force coupling may likewise vary, possibly affecting the capacity for active knee stabilization. The purpose of this study was to assess the effect of changes in movement speed and joint position on eccentric/concentric muscle action relationships in the knees of uninjured (UNI) and post-ACL-surgery (INJ) subjects (n = 14). All subjects were tested for maximum eccentric and concentric torque of the contralateral knee flexors and extensor muscles at four isokinetic speeds (15 degrees-60 degrees x s(-1)) and four joint position intervals (20 degrees-60 degrees of knee flexion). Eccentric flexor torque was normalized to the percentage of concentric flexor torque generated at each joint position interval for each speed tested (flexor E-C ratio). In order to estimate the capacity of the knee flexors to resist active knee extension, the eccentric-flexor/concentric-extensor ratios were also computed for each joint position interval and speed (flexor/extensor E-C ratio). The results revealed that eccentric torque surpassed concentric torque by 3%-144% across movement speeds and joint position intervals. The magnitude of the flexor E-C ratio and flexor/extensor E-C increased significantly with speed in both groups of subjects (P < 0.05) and tended to rise with muscle length as the knee was extended; peak values were generated at the most extended joint position (20 degrees-30 degrees). Although torque development patterns were symmetrical between the contralateral limbs in both groups, between-group comparisons revealed significantly higher flexor/extensor E-C ratios for the INJ group compared to the UNI group (P < 0.05), particularly at the fastest speed tested (60 degrees x s(-1)). The results indicate that joint position and movement speed influence the eccentric/concentric relationships of knee flexors and extensors. The INJ subjects appeared to accommodate to surgery by developing the eccentric function of their ACL and normal knee flexors, particularly at higher speeds and at more extended knee joint positions. This may assist in the dynamic stabilization of the knee at positions where ACL grafts have been reported to be most vulnerable to strain.

Adult↗
PubMed1996

Eccentric knee flexor torque following anterior cruciate ligament surgery.

The purposes of this study were to compare eccentric knee flexor torque and muscle activation in the limbs of normal (NOR) subjects and in subjects who had undergone unilateral ACI, autograft surgical reconstruction (INJ) and to assess the effect of movement speed on EMG/ torque ratios and eccentric-concentric actions. Fourteen subjects (7 NOR and 7 INJ) were tested for knee eccentric flexor torque and EMG activity at four isokinetic speeds (15 degrees, 30 degrees, 45 degrees and 60 degrees.s-1). Results revealed that post-surgical limbs (ACL) produced significantly less (P < 0.05) eccentric torque and flexor EMG activity at 60 degrees.s-1 than uninjured (UNI) contralateral limbs. Eccentric torque rose significantly as speed increased from 45 degrees to 60 degrees.s-1 for surgical group uninjured limbs and NOR group left and right limbs. Eccentric flexor torque increased with speed for both groups and approximated equality with concentric extensor torque at 60 degrees.s-1 for INJ group ACL and UNI limbs. Concentric flexor muscle EMG/torque ratios were 30-191% greater than eccentric muscle actions across groups and speeds. The results suggest that ACL dysfunction may result in reduced eccentric flexor torque at rapid movement speeds, that eccentric flexor torque increases with movement speed and may have the capacity to counter forceful extensor concentric torque, and that eccentric muscle actions produce less muscle activation per unit force than concentric actions which may reflect reduced energy cost.

Adult↗
PubMed1995

Contralateral hamstring (biceps femoris) coactivation patterns and anterior cruciate ligament dysfunction.

It has been postulated that coactivation of antagonist hamstring musculature during active knee extension aids the anterior cruciate ligament (ACL) in maintaining joint stability by exerting an opposing torque to anterior tibial displacement induced by the quadriceps. It was the purpose of this study to compare contralateral patterns of hamstring coactivation in subjects who have suffered ACL dysfunction with subjects who have normal knees. Five subjects who had suffered ACL dysfunction (INJ) and five uninjured (UNI) subjects performed maximal flexions and extensions of the knee on a modified isokinetic dynamometer at 100 degrees and 300 degrees.s-1. Simultaneous recordings of torque, angular displacement, and electromyographic (EMG) activity from the hamstring musculature were computer processed. No significant differences (P < 0.05) in torque were found between ACL/normal and right/left limbs for the INJ and UNI groups, respectively. For the INJ subjects, mean coactivation of the normal limb hamstrings during extension averaged twice that of the ACL limb. In contrast, no significant difference was found for the same comparison between right and left limbs in the UNI group. The results of this study suggest that asymmetry in hamstring coactivation during knee extension may result from ACL dysfunction.

Adult↗
PubMed1994

Medial tibial stress syndrome. The location of muscles in the leg in relation to symptoms.

The legs of fifty cadavera were dissected to identify accurately the structures that attach to the tibia at the site of symptoms of medial tibial stress syndrome and that could potentially contribute to this condition. The origins of the soleus, the flexor digitorum longus, and the tibialis posterior muscles as well as that of the deep crural fascia were measured. The average sites of attachment and the ranges of attachment were determined for each structure. The soleus, the flexor digitorum longus, and the deep crural fascia were found to attach most frequently at the site where symptoms of medial tibial stress syndrome occur, while in no specimen was the tibialis posterior found to attach at this site. The data support recent reports that the soleus is probably the major contributor to traction-induced medial tibial stress syndrome. The data also contradict the contention that the tibialis posterior may contribute to this particular condition.

Aged↗
PubMed1990

Differential responses to proprioceptive neuromuscular facilitation (PNF) stretch techniques.

The purpose of this study was to investigate the effects of sustained stretch and two common proprioceptive neuromuscular facilitation (PNF) stretch techniques on hamstring muscle activation and knee extension range of motion (ROM) in different athletic populations. Three stretch techniques: stretch-relax (SR), contract-relax (CR), and agonist contract-relax (ACR) were applied to 10 endurance athletes (EN), 10 high intensity athletes (HI), and 10 control subjects (C). The results revealed that ACR produced 89-110% greater hamstring EMG activity (P less than 0.05) and 9-13% more knee joint ROM than CR and SR, respectively. This same pattern was evident for the individual subject groups. Comparisons of mean data among the three subject groups revealed that the EN athletes generated 58-113% more hamstring EMG activity (P less than 0.05) than the HI and C groups, respectively, across all stretch conditions, whereas the EN group attained significantly less ROM than the HI and C groups for CR and ACR conditions. It was postulated that high intensity-short term activity training necessitates less hamstring resistance to knee extension than long term endurance training. The findings suggest that decreases in muscle activity may not be strongly related to increases in joint range of motion and that factors other than muscle relaxation are important in achieving increased ROM. Also, the differential effects of various stretch techniques between dissimilar athletic populations should be considered if stretch-induced injury is to be avoided.

Adult↗
PubMed1990

Isokinetic evaluation of quadriceps and hamstrings symmetry following anterior cruciate ligament reconstruction.

After anterior cruciate ligament (ACL) reconstruction, isokinetic muscle parameters are commonly measured to assess the dynamic status of the knee and to monitor progress in rehabilitation. This study evaluated the symmetry of the quadriceps and hamstrings musculature in postsurgical and contralateral normal limbs of subjects who had undergone one of two types of ACL reconstruction. Subjects were also evaluated for differences on selected isokinetic parameters between types of surgery and lengths of postoperative periods. Postsurgical and normal contralateral limbs of 46 subjects aged 18 to 49 years (mean, 23.7 years) were divided into groups according to type of autogenous intraarticular ACL substitute and length of postoperative period. Results of paired t-tests and analyses of variance indicated significant asymmetries between limbs for all measures of quadriceps and hamstrings musculature strength and endurance (p less than .001) irrespective of the type of reconstruction technique. Average surgical knee deficits in hamstrings endurance were significantly less for the long-term (41 to 101 months) follow-up group (1.9%) than for the intermediate (24 to 40 months) group (12.1%). The results suggest that extended periods of time are required to approximate hamstrings endurance symmetry after ACL reconstruction. Asymmetries between postsurgical and contralateral normal limbs in these subjects may reflect either incomplete rehabilitation or an inability to regain full isokinetic strength and endurance after ACL reconstruction.

Adult↗
PubMed1989

Instrumented Lachman tests for the evaluation of anterior laxity after reconstruction of the anterior cruciate ligament.

Using a KT-1000 arthrometer, in fifty subjects were measured the anterior ligamentous laxity in a knee in which the anterior cruciate ligament had been reconstructed and in the normal, contralateral knee. We also determined the anterior tibial displacement and anterior compliance, using the Lachman test. The subjects were divided into groups according to the type of autogenous intra-articular substitute (either the central one-third of the patellar tendon or the semitendinosus tendon) that had been used for the anterior cruciate ligament and according to the duration of follow-up (range, twenty-four to 101 months). Lachman tests were performed, applying sixty-eight and ninety newtons of force, and indices for anterior compliance were calculated. Although significantly more anterior laxity was demonstrated with both sixty-eight and ninety newtons of force in the reconstructed knees than in the contralateral, normal knees (p less than 0.001), thirteen subjects, of whom eight lacked full extension of the reconstructed knee, had more anterior laxity in the normal knee. Analyses of variance showed no significant differences in the results of the Lachman tests as related to either the type of reconstruction or the length of postoperative follow-up. The results suggested that the two types of ligamentous substitute that were used in this study were equally efficient in limiting anterior tibial displacement, as demonstrated by the Lachman test. The study also demonstrated that the substitutes did not elongate significantly during the period of the study.

Adolescent↗
PubMed1987

Muscle activation during proprioceptive neuromuscular facilitation (PNF) stretching techniques.

Proprioceptive neuromuscular facilitation (PNF) techniques are often used to induce muscle relaxation and increase joint range of motion (ROM). However, the relationship between muscle activation and ROM with PNF is not well understood. The purpose of this study was to investigate the effect of three common PNF stretching techniques on hamstring muscle activation and knee extension. Three PNF techniques: stretch-relax (SR), contract-relax (CR) and agonist contract-relax (ACR) were applied to ten male and female subjects aged 23-36 years who were stabilized to isolate knee extension measurements. Knee joint position and EMG activity from quadriceps and hamstring muscles were computer processed throughout technique application. The results revealed mean hamstring EMG activity increased 8-43% within a given trial of ACR and CR respectively, and did not diminish across trials. SR produced a 11% decrease in mean hamstring EMG activity. ACR produced 3-6% greater knee extension values than CR and SR respectively, in spite of 71-155% greater hamstring EMG activity during ACR. The data suggest that CR and ACR do not evoke sufficient relaxation in muscles opposing knee extension to overcome tension facilitation generated by stretch. Thus, increases in ROM are achieved while the hamstrings are under considerable tension. Such tension increases muscle vulnerability to soreness and strain if stretching continues. The degree of knee extension produced via SR, although 3-6% less than CR and ACR, was achieved during simultaneous reduction in hamstring activity and may be the safer stretching technique.

Adult↗
PubMed1986

Isokinetic dynamometry: implications for muscle testing and rehabilitation.

Isokinetic exercise has become an increasingly popular modality in rehabilitative medicine during the past decade. The facility by which isokinetic dynamometers provide information about dynamic muscle contractions has, no doubt, been a major factor in this popularity. Isokinetic dynamometers are passive devices which resist applied forces and control the speed of exercise at a predetermined rate. Such dynamometers generally provide a record of applied force throughout a joint range of motion. Some of the postulated advantages of isokinetic exercise include safety, accommodating resistance and the facility for muscle force analysis. In spite of the advantages that isokinetic dynamometry provides, there are a number of considerations that are important in the interpretation of force recordings. While the term "isokinetics" generally denotes a type of muscular contraction which accompanies a constant rate of limb movement, periods of acceleration and deceleration exist in the context of isokinetic exercise. The acceleration and subsequent oscillatory and deceleration periods of "isokinetic" exercise limit the duration of the period of constant velocity in exercises with isokinetic dynamometry. Impact artifacts on torque records result from the compliance of the dynamometer system as it adjusts the accelerating limb to the present speed. The position at which peak torque occurs in a joint range varies with speed of motion. Therefore, analysis of maximal values at specific joint angles across speeds should be made in addition to the peak values generated throughout a joint range. The shape of the isokinetic force-velocity curve differs from the classic curve derived from prepared muscle specimens. As speed approaches zero, the isokinetic muscular force tends to rise much less steeply than that of the in vitro curve. Because measurements of absolute maximal force or velocity are subject to constraints in human studies, the direct comparison of in vivo to in vitro force-velocity curves is not justified. Neural inhibition of the force generated in intact muscle as tension rises has been postulated as a possible mechanism retarding the force curve at slow speeds. The reliability of specific types of isokinetic dynamometers appears to be quite high when test-retest analyses are performed with inert weights. Whether submaximal or maximal warm-ups are essential to ensure stable measures is still questionable at this time. It seems prudent to recommend submaximal warm-ups prior to maximal testing in order to reduce the possibility of muscle strain.(ABSTRACT TRUNCATED AT 400 WORDS)

Exercise Therapy↗
PubMed1986

Co-activation of sprinter and distance runner muscles in isokinetic exercise.

The purpose of this study was to investigate the extent of co-activation of quadriceps and hamstring musculature in sprinters and distance runners. Nine female intercollegiate track athletes performed maximal knee extensions and flexions on a modified orthotron isokinetic dynamometer at two speeds (100 degrees and 400 degrees X s-1). Simultaneous recordings of torque, joint position, and agonist/antagonist electromyographic activity from the quadriceps and hamstrings were computer-processed. The results revealed the hamstrings to be considerably more active during knee extension than the quadriceps during flexion. The integrated electromyographic activity of co-contracting hamstrings and quadriceps, throughout the joint range, averaged 33 and 6%, respectively, of the same muscle group during its agonist phase. Hamstring co-activation increased sharply during the last 25% of knee extension, generating 58% of the integrated electromyographic agonist activity. Co-activation of the sprinters' hamstrings was four times that of distance runners (57/14%), however, the faster speed of movement (400 degrees X s-1) increased hamstring coactivation of distance runners more acutely than sprinters in the final phase of extension. The data suggest that the hamstrings are used to a much greater extent than quadriceps for limb deceleration and that the distraction of antagonist muscle tension should be considered when analyzing agonist isokinetic torques. Furthermore, the relatively high co-activation of the hamstrings, particularly during the last 25% of extension, may induce hamstring soreness or strain in vulnerable subjects.

Adult↗
PubMed1984

Electromyographic patterns accompanying isokinetic exercise under varying speed and sequencing conditions.

The purposes of this study were: a) to investigate electromyographic patterns accompanying isokinetic exercise under varying speed and sequencing conditions, and b) to investigate the role of antagonist coactivation under these same conditions. Five adult males performed maximal knee extensions and flexions on a modified Orthotron isokinetic dynamometer. Tests were done at four speeds (100-400 degrees/sec) and under two counterbalanced conditions: extension followed by flexion (E/F) and flexion followed by extension (F/E). Simultaneous recordings of torque, knee joint position and agonist/antagonist EMG changes from the quadriceps and hamstring musculature were collected and analyzed. No consistent EMG patterns emerged that inferred intermittent surges of muscular activity as the primary mechanism yielding double peaked torques that characteristically occur in isokinetic exercise. Further analyses revealed relatively small co-contractions of antagonists during the various phases of movement. The findings suggest that gravity and inertia of the limb/lever system were the major factors responsible for limb deceleration and substantive antagonist co-contraction was not required for braking. If isokinetic knee flexion and extension exercises are used for conditioning or developmental purposes of healthy subjects, any distraction of the co-contracting antagonist from the recorded force of the agonist appears to be small once the activity is learned.

Adolescent↗
PubMed1983

An assessment of subject variability, subject-shoe interaction, and the evaluation of running shoes using ground reaction force data.

Several aspects of dynamic foot function were investigated using ground reaction forces obtained from five runners performing in five different shoes. A minimum of eight trials were necessary in order to obtain stable subject-condition values. Statistically significant subject-shoe interactions occurred for all parameters. It was therefore concluded that a knowledge of shoe characteristics independent of subject characteristics provided little useful information regarding the effects of the shoes tested on selected foot mechanics of the runners. The various subject-conditions were evaluated in an attempt to determine which was the best shoe. Selected descriptive data are presented and the 'best' shoe concept discussed.

Biomechanical Phenomena↗
PubMed1981

Relationships between tibial rotary torque and knee flexion/extension after tendon transplant surgery.

The hamstring muscles play an important role in decelerating and checking tibial rotation before excessive stresses are applied to knee support structures. The purpose of this study was to determine the relationships between standard flexion/extension rehabilitative techniques and tibial rotary torque among subjects who had received pes anserinus transfers at least 1 year prior. Postsurgical and healthy contralateral limbs of 15 males were tested for maximum, isokinetic knee flexion/extension and internal/external tibial rotation. An adjustable chair and stabilizing boot were used to minimize extraneous hip, thigh and subtalar movements. Product-moment correlation coefficients were computed to determine the relationships between muscle forces generated during tibial rotation and knee flexion/extension. Relatively small relationships were found between rotation and flexion. Tibial rotation and flexion were more highly correlated in the nonsurgical than in the surgical limbs. The results also revealed that peak torque was generated within the first 5-10 degrees of motion for tibial rotation and within the first 20-30 degrees of motion for knee flexion and extension. The data indicate that measures of maximal knee flexor torque cannot be used to predict the rotational capabilities of the same muscle group and that separate measurement and rehabilitative techniques are necessary. Further analyses of postsurgical knees revealed force deficits among knee flexors and extensors when compared to nonsurgical counterparts. The findings suggest long-term sensitivity of the quadriceps to immobility.

Adolescent↗