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At least 1,099 records · Page 61Linked to original sources
PubMed2000

Do the hamstrings and adductors contribute to excessive internal rotation of the hip in persons with cerebral palsy?

Children with cerebral palsy frequently walk with excessive internal rotation of the hip. Spastic medial hamstrings or adductors are presumed to contribute to the excessive internal rotation in some patients; however, the capacity of these muscles to produce internal rotation during walking in individuals with cerebral palsy has not been adequately investigated. The purpose of this study was to determine the hip rotation moment arms of the medial hamstrings and adductors in persons who walk with a crouched, internally-rotated gait. Highly accurate computer models of three subjects with cerebral palsy were created from magnetic resonance images. These subject-specific models were used in conjunction with joint kinematics obtained from gait analysis to calculate the rotational moment arms of the muscles at body positions corresponding to each subject's internally-rotated gait. Analysis of the models revealed that the medial hamstrings, adductor brevis, and gracilis had negligible or external rotation moment arms throughout the gait cycle in all three subjects. The adductor longus had an internal rotation moment arm in two of the subjects, but the moment arm was small (<4 mm) in each case. These findings indicate that neither the medial hamstrings nor the adductor brevis, adductor longus, or gracilis are likely to be important contributors to excessive internal rotation of the hip. This suggests that these muscles should not be lengthened to treat excessive internal rotation of the hip and that other factors are more likely to cause internally-rotated gait in these patients.

Adolescent↗
PubMed1984

On hip and lumbar biomechanics. A study of joint load and muscular activity.

Loading moment of force about the hip and lumbo-sacral joints during straight and flexed knee lifting was calculated at regular intervals during the lifts, using a computerized sagittal plane model. Lift with flexed knees and burden moved close to the body was found to induce lower load. Important parameters influencing the induced joint load are discussed. EMG levels from three trunk and seven hip muscles were recorded with surface electrodes and normalized, i.e. expressed as a percentage of the recorded level of each muscle during an isometric voluntary contraction. The erector spinae, gluteus maximus and adductor magnus muscles were more activated initially in the flexed knee lifts than in the straight knee lift, while the hamstrings were more and earlier activated in the flexed knee lifts. In order to estimate what proportion of the maximum hip extensor muscle moment was used to counteract the induced load moments about the hip, assessments of maximum hip extensor muscle moments were made: the highest extensor muscle moment was exerted at 90 degrees hip flexion, decreasing with decreasing hip angle. The knee angle did not significantly influence the muscle moments exerted by the hip extensor muscles. To calculate the magnitude and direction of the hip compressive load from known load moments, the length of the moment arms of three hip extensors was determined at every fifth degree of flexion at hip flexion angles between 0 degrees and 90 degrees by combining data from autopsy specimens and patients, the latter examined by computed tomography. There were significant differences in moment arm length between men and women but there was low correlation between subject's height and length of muscular moment arms. The calculated compressive force during the lifts was about three times body weight and the direction of the compressive force passed through the area described by others as having the most severe osteoarthrotic lesions on the femoral head. Hip joint load moments and normalized EMGs from five hip muscles were assessed during rising exercises for the lower limb in order to determine to what extent joint load and EMG is influenced by adaptive adjustments of the exercise. A multicomponent force-measuring platform and pictures on cine-film were used in the calculations of load moments. Posterior foot position lowered the load moment and slightly increased the level of muscular activity in the hip extensors. The design and use of a force prediction diagram for estimating induced hip extensor muscular forces is described.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1997

The muscles in chronic ligamentous instability of the knee: an experimental study.

Several authors have formulated the idea that insufficiency of the anterior cruciate ligament (ACL) might lead to a biological adaptation, consisting of atrophy of the quadriceps and other extensors (antagonists of the ACL) and relative preservation of the hamstrings and other flexors (agonists of the ACL). We studied the modifications in hindlimb muscles that spontaneously occurred in 36 rabbits with surgically-induced chronic ligamentous instability of the right knee. The unoperated left hindlimb served as a control. Three months after surgery the rabbits were sacrificed and the muscles dissected for macroscopic and microscopic evaluation. In the anterior cruciate ligament-deficient limbs the extensors (quadriceps, glutei and extensor digitorum longus) showed significantly greater atrophy than the other muscles (p < 0.05). Six hundred twenty-two fibers from atrophic muscles, 373 from hypertrophic muscles and 879 from control muscles were evaluated by microscopy. The atrophic muscles showed a significantly lower percentage of type I fibers (responsible for maintenance of posture) and a reduction in the diameter of both type I and II (responsible for rapid movement) fibers with respect to the controls (p < 0.05). The hypertrophic muscles showed a significantly greater proportion of type I fibers and an increase in the diameter of type II fibers with respect to the controls (p < 0.05). Our results support the idea that there is spontaneous adaptation of the muscles to compensate for ligamentous instability.

Adaptation, Physiological↗
PubMed1987

Effects of arm acceleration and behavioral conditions on the organization of postural adjustments during arm flexion.

Nine standing subjects performed unilateral arm flexion movements over an eight-fold range of speeds, under two behavioral conditions. In the visually-guided condition, a visual target informed subjects about the correct movement speed. Seven subjects also made movements of different speeds during a self-paced condition, without a visual target. Angular displacement and acceleration of the arm, and EMG activity from the hamstrings (HM), erector spinae (ES) and the anterior deltoid (AD) muscles were measured. The following results were observed. Mean rectified amplitudes of EMG activity in HM and ES were typically correlated with the average arm acceleration and presumably the disturbance to posture and/or balance. HM and ES amplitudes were correlated for only six subjects. Functions relating the ratios of HM/ES EMG amplitudes to acceleration varied between subjects. HM onset latencies were highly variable for slow movements and usually lagged movement. For movements above a threshold-like point in acceleration, HM latencies were correlated with arm acceleration and recruited before movement. ES latencies were constant for fast movements, and negatively correlated with acceleration for slower movements. The recruitment order of HM and AD was influenced by the behavioral condition but not by arm acceleration for fast movements. HM and AD were recruited coincidentally for visually-guided movements, while for self-paced movements, HM was recruited before AD. We conclude that for the arm flexion task: HM and ES are not tightly coupled; both behavioral and mechanical conditions affect the recruitment of postural muscles; and postural and focal components of the movement are probably organized by parallel processes.

Acceleration↗
PubMed1997

Reduced muscle function in patients with osteoarthritis.

The purpose of this study was to determine whether subjects with knee osteoarthritis (OA) had reduced muscle strength at various muscle lengths, endurance, contraction velocity and functional capacity, compared with control subjects and whether the decrease was related to functional capacity. Forty-five men and 45 women with knee OA were compared with a control group (41 males, 63 females) of similar age for functional capacity, maximal isometric strength (in vivo length-tension relationship) and endurance (in vivo force-time relationship) of knee flexion and extension and maximal angular velocity (in vivo force-velocity relationship) of knee extension. The OA subjects had increased difficulty (2.03 +/- 0.53) and pain (1.65 +/- 0.29) for activities of daily living (ADLs) and significantly lower strength for extension (72%) and flexion (56%), endurance for the quadriceps (203%) and hamstrings (214%) and velocity (128%). The reductions were greater at longer muscle lengths. These data demonstrate that patients with knee OA have reduced muscle function and functional capacity compared to controls.

Aged↗
PubMed2001

Rotational moment arms of the medial hamstrings and adductors vary with femoral geometry and limb position: implications for the treatment of internally rotated gait.

Persons with cerebral palsy frequently walk with a crouched, internally rotated gait. Spastic medial hamstrings or adductors are presumed to contribute to excessive hip internal rotation in some patients; however, the capacity of these muscles to produce internal rotation has not been adequately investigated. The purpose of this study was to determine the hip rotation moment arms of the medial hamstrings and adductors in persons with femoral anteversion deformities who walk with a crouched, internally rotated gait. A musculoskeletal model with a "deformable" femur was developed. This model was used, in conjunction with kinematic data obtained from gait analysis, to calculate the muscle moment arms for combinations of joint angles and anteversion deformities exhibited by 21 subjects with cerebral palsy and excessive hip internal rotation. We found that the semimembranosus, semitendinosus, and gracilis muscles in our model had negligible or external rotation moment arms when the hip was internally rotated or the knee was flexed -- the body positions assumed by the subjects during walking. When the femur was excessively anteverted, the rotational moment arms of the adductor brevis, adductor longus, pectineus, and proximal compartments of the adductor magnus in our model shifted toward external rotation. These results suggest that neither the medial hamstrings nor the adductors are likely to contribute substantially to excessive internal rotation of the hip and that other causes of internal rotation should be considered when planning treatments for these patients.

Adolescent↗
PubMed2000

Characterization of hamstring reflexes during anterior cruciate ligament disruption: in vivo results from a goat model.

The existence of an anterior cruciate ligament-hamstring reflex arc, the extent to which these reflexes can protect the knee, and the extent to which they are affected by rupture of the anterior cruciate ligament remain controversial. We evaluated the temporal components of the anterior cruciate ligament-hamstring synergy by simulating an injury to the ligament in a goat model. Reflexive hamstring activation in anesthetized goats was evaluated when the anterior cruciate ligament was loaded with static subfailure, dynamic subfailure, and dynamic failure loads. Reflexive hamstring activation was not found in response to static subfailure loading but was observed in response to dynamic subfailure and failure loading. The latency of the reflex evoked by dynamic failure loading was shorter than that evoked by dynamic subfailure loading. The findings suggest that the extent to which the hamstring reflexes can protect the knee may be bounded by the ability of these muscles to generate force rapidly and the amplitude and time-course of the loads applied to the knee joint. The present data present a framework for further investigation of the contribution of anterior cruciate ligament-hamstring reflexes to the stability of the knee joint under high loads and loading rates.

Animals↗
PubMed2003

The effect of previous weight training and concurrent weight training on endurance for functional electrical stimulation cycle ergometry.

Forty-five paraplegic subjects participated in three series of experiments to examine the interrelationships between previous weight training, concurrent weight training and muscle strength and endurance during cycle ergometry elicited by functional electrical stimulation (FES). When subjects only underwent isokinetic weight training (series 1) three times per week on the quadriceps, hamstring and gluteus maximus groups for 12 weeks, strength increased linearly with time for all three muscle groups from an initial average of 17 N to 269 N at the end of training, a 15-fold increase. In the second series of experiments, different groups of subjects either underwent no strength training prior to cycle ergometry or underwent strength training of these same three muscle groups for 2 weeks, four weeks, or 6 weeks prior to cycle ergometry. Any strength training was effective in increasing endurance for cycle ergometry. However, the rate of increase in endurance during cycle ergometry with no prior strength training was only 5 min per week, whereas the rate of increase in cycle endurance during ergometry was 14.6, 25.0, and 33.3 min per week increase in endurance after strength training for 2.4 and 6 weeks, respectively. When weight training was accomplished during FES cycle ergometry (concurrently) in a third series of experiments, there was an additional increase in endurance during cycling if strength training was concurrently accomplished. With no weight training, endurance increased 23 min per week, whereas with concurrent weight training at three times per week, endurance increased during cycling by 41.6 min per week. The results of these experiments seem to show a clear advantage of weight training concurrently and before FES cycle ergometry. Results are given as mean (SD).

Adult↗
PubMed1988

EMG profiles of knee joint musculature during walking: changes induced by anterior cruciate ligament deficiency.

A tear of the anterior cruciate ligament (ACL) disrupts the delicate balance of static stabilizers of the knee, leading to significant alterations in joint kinematics. Little is known about the dynamic compensatory responses of the patient to these kinematic alterations. This lack of quantitative information on the muscle synergy patterns has limited the surgeon's ability to evaluate various operative and rehabilitative techniques. Twelve subjects with documented ACL deficiency for at least 1 year and 15 normal participants were studied. Each subject was asked to walk at free and fast speeds on a 12 m walkway. The right and left foot contact patterns and the linear envelopes from the surface electromyogram (EMG) patterns of the gastrocnemius, medial and lateral hamstrings, rectus femoris, and vastus lateralis were measured. Significant differences were found in the muscle synergy patterns during walking. During the swing-to-stance transition, the ACL-deficient subjects showed significantly less activity in the quadriceps and gastrocnemius muscles and more activity in the biceps femoris than in the normal group. During early swing, the vastus lateralis is more active than normal, and during midstance and terminal stance, the hamstrings appear to be less active than normal subjects. These dynamic compensatory mechanisms suggest that use of the hamstring tendons in reconstructive procedures may alter important compensatory mechanisms about the knee joint. Application of dynamic EMG techniques to the study of reconstructive procedures should provide additional information that will assist the clinician in the rational choice of a surgical procedure.

Adult↗
PubMed2000

Could different directions of infant stepping be controlled by the same locomotor central pattern generator?

This study examined the idea of whether the same central pattern generator (CPG) for locomotion can control different directions of walking in humans. Fifty-two infants, aged 2-11 mo, were tested. Infants were supported to walk on a treadmill at a variety of speeds. If forward stepping was elicited, stepping in the other directions (primarily sideways and backward) was attempted. The orientation of the infant on the treadmill belt determined the direction of stepping. In some infants, we also attempted to obtain a smooth transition from one direction to another by gradually changing the orientation of the infant during a stepping sequence. Limb segment motion and surface electromyography from the muscles of the lower limb were recorded. Most infants who showed sustained forward walking also could walk in all other directions. Thirty-three of 34 infants tested could step sideways. The success of eliciting backward stepping was 69%. Most of the infants who did not meet our backward stepping criteria did, however, make stepping movements. The different directions of stepping had similar responses to changes in treadmill speed. The relationship between stance and swing phase durations and cycle duration were the same regardless of the direction of stepping across a range of speeds. Some differences were noted in the muscle activation patterns during different directions of walking. For example, the hamstrings were much more active during the swing phase of backward walking compared with forward walking. The quadriceps was more active in the trailing leg during sideways walking. In some infants, we were able to elicit stepping along a continuum of directions. We found no discrete differences in either the electromyographic patterns or the temporal parameters of stepping as the direction of stepping was gradually changed. The results support the idea that the same locomotor CPG controls different directions of stepping in human infants. The fact that most infants were able to step in all directions, the similarity in the response to speed changes, and the absence of any discrete changes as the direction of stepping was changed gradually are all consistent with this hypothesis.

Brain Stem↗
PubMed1993

Impact of knee extensor strength deficits on stair ascent performance in patients after medial meniscectomy.

After arthroscopic meniscectomy the relationship between the magnitude of knee extensor strength deficits and locomotor performance during stair ascent unloaded and when carrying a 22 kg load has been tested in 31 patients. The specific locomotor adaptations related to large strength deficits were also studied. The results indicate that large deficits were significantly associated to: 1) reduced activation of the knee extensor muscles (vastus medialis and lateralis) during the first double leg support and single leg support phases, and of the hip extensors (medial hamstrings) during the second double leg support of stair ascent, 2) overactivations of the hip extensors (gluteus maximus and medial hamstrings) during single leg support, and 3) longer cycle and step durations and lower cadences. Locomotor abnormalities in movements and muscle activations were generally found in patients with strength deficits greater than 25% while patients with smaller strength deficits (less than 25%) usually could climb stairs with normal performance. These results support the use of knee extensor strength measures to predict locomotor capacities, and also highlight the importance of postoperative knee strength rehabilitation.

Adaptation, Physiological↗
PubMed1984

Hip load moments and muscular activity during lifting.

The load on the hip joint during lifting was studied. Healthy subjects lifted a 12.8 kg box from floor to table level with straight and flexed knees in four different ways. The loading moment of force about the bilateral hip axis was calculated by means of a computerized static sagittal plane model. The highest load moment, 124 Nm, occurred initially in the straight knee lift and the compressive joint reaction force was 2.7 times body-weight. The lowest load moment, 82 Nm, occurred in the flexed knee lift with the burden moved close to the trunk, the compressive force was 3.2 X bw. The load moment was also discussed in relation to the strength capability. The EMG levels of seven different hip muscles were normalized and expressed as a percentage of the recorded level of each muscle group during an isometric maximum voluntary contraction. The initial activity in the hamstrings was higher in the straight knee lift compared to flexed knees. The gluteus maximus was activated to a moderate level.

Adult↗
PubMed1992

[A comparison of fat and muscle thickness in Japanese and American women].

The purpose of this study was to investigate the ethnic differences in the body composition, thickness of subcutaneous fat and muscle between Japanese and American white females. Thirty-six Japanese (aged 20-30 years) and 42 American white females (aged 20-29 years) served as subjects. Percentage of fat weight (%fat) and fat free weight (FFW) were assessed by hydrostatic weighing. Subcutaneous fat and muscle thickness were measured by using B-scan ultrasound equipment with a 5MHz transducer at eight sites: forearm, biceps, triceps, subscapular, abdomen, quadriceps, hamstrings and posterior calf. There were no significant differences in %fat between Japanese and American subjects. However, American subjects had significantly higher values in FFW compared to Japanese. The Americans showed higher muscle thickness than Japanese at every site and higher fat thickness of biceps, triceps and hamstrings compared to Japanese subjects. For fat thickness at the abdomen, however, Japanese indicated significantly higher values than American. In both Japanese and Americans, relative values of fat weight (FW) and FFW per unit of height were significantly related to each of the sum of fat and muscle thicknesses obtained from every measurement site respectively. There were no differences in fat thickness at a given FW/height between Japanese and Americans.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗
PubMed1976

The action of the hind limb musculature of the dog in walking.

This study was performed by means of cinephotography and electromyography. The results were correlated with earlier investigations concerning the forces exerted by the pads of walking dogs. A concept about the action of individual muscles of the hind limb during a stride was formed. The principal conclusions are: (1) The hamstrings are divisible into a cranial and a caudal group, the first consisting of the cranial parts of the M. biceps femoris and M. semimembranosus, the second of the caudal parts of these muscles, together with the M. semitendinosus. The chief function of both groups is to extend the hip; the caudal group also flexes the stifle. (2) Activity is present in the greatest number of muscle s during the change in the sense of movement of the limb. (3) During the last stages of the stance phase the number of muscles showing electrical activity diminishes, while the force exerted by the pads in a horizontal direction increases. Non-muscular forces, e.g. inertia, play an important role during movement.

Animals↗
PubMed1996

Hamstring injuries.

Explore the source record for details and available documents.

Athletic Injuries↗
PubMed1981

Function after removal of various hip and thigh muscles for extirpation of tumors.

Forty-six patients who had undergone excision of one or more well defined hip and/or thigh muscles because of a soft-tissue tumor or a tumoriform lesion were investigated with respect to the function of the operated limb and the isometric and isokinetic strength of the affected motion or motions, relative to the non-operated side (percentage). Hip flexion: Loss of the iliopsoas caused slight impairment of function. The flexion strength decreased with increasing flexion of the hip joint. Loss of the rectus femoris reduced the isometric strength by 37 and the isokinetic strength by 17 per cent. Hip abduction: The strength reduction was only about 50 per cent and the impairment of function only slight or moderate even in patients with extensive loss of abductor muscles. Hip adduction: Removal of all three prime adductors (longus, brevis, magnus) caused a strength reduction of about 70 per cent but the impairment of function was only slight or moderate. Hip extension: Loss of the gluteus maximus caused only a small strength reduction and no impairment or only slight impairment of function. Significant strength reduction was only seen when all hamstrings had been removed. Knee extension: Loss of one, two, and three of the quadriceps muscles reduced the isometric strength by 22, 33, and 55 per cent, respectively. The isokinetic strength was reduced somewhat more. The strength reduction usually had to exceed 50 per cent to cause more than slight impairment of function. Knee flexion: Loss of the semitendinosus, the biceps femoris, and all the hamstrings reduced the isometric strength by 24, 28, and 67 per cent, respectively. The isokinetic strength was reduced somewhat less. Loss of one of the hamstrings usually caused no impairment of function whereas loss of all three resulted in moderate impairment of function.

Adolescent↗