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At least 487 records · Page 27Linked to original sources

PubMed2004

Are hamstrings activated to counteract shear forces during isometric knee extension efforts in healthy subjects?

The hamstring muscles have the potential to counteract anterior shear forces at the knee joint by co-contracting during knee extension efforts. Such a muscle recruitment pattern might protect the anterior cruciate ligament (ACL) by reducing its strain. In this study we investigated to what extent co-activation of the knee flexors during extension efforts is compatible with the hypothesis that this co-activation serves to counteract anterior tibial shear forces during isometric knee extension efforts in healthy subjects. To this aim, it is investigated whether co-activation varies with the required knee extension moment, with the knee joint angle, and with the position of the external flexing force relative to the knee joint. With unaltered moment and muscle activation, distal positioning of the flexing force on the tibia causes higher resultant (muscular plus external) forward shear forces at the knee as compared to proximal positioning. In ten subjects, knee flexor and extensor EMG was measured during a quasi-isometric positioning task for a range (5-50 degrees) of knee flexion angles. It was found that the co-activation of the knee flexors increased with the extension moment, but this increase was less than proportional (p<0.001). The extension moment increased 2.7 to 3.4 times, whereas the activation of Biceps Femoris and Semitendinosus increased only a factor 1.3 to 2.0 (joint angle dependent). Furthermore, a strong increase in co-activation was seen near full extension of the knee joint. The position of the external extension load on the tibia did not affect the level of co-contraction. It is argued that these results do not suggest a recruitment pattern that is directed at reduction of anterior shear forces in the knee joint during sub-maximal isometric knee extension efforts in healthy subjects.

Adaptation, Physiological↗

PubMed2000

A ganglion cyst causing lumbar radiculopathy in a baseball pitcher: a case report.

This report describes a case of a professional baseball pitcher who developed acute left lumbar radicular symptoms after a baseball game and was subsequently sidelined for the rest of the season. Physical examination revealed depressed reflexes in the left posterior tibialis and left medial hamstring muscles, mild weakness in the left extensor hallucis longus, and positive dural tension signs. Magnetic resonance imaging demonstrated an ovoid mass at the L4-L5 level, causing compression of the dura. Surgical resection of the mass resulted in resolution of his symptoms. Pathology revealed that the mass was a ganglion cyst. A ganglion cyst is a rare cause of lumbar radiculopathy and should be considered in the differential diagnosis if a patient with lumbar radiculopathy fails to respond to conservative treatment.

Adult↗

PubMed2003

Spastic velocity threshold constrains functional performance in cerebral palsy.

OBJECTIVES: To evaluate a quantitative, velocity-based assessment of spasticity in the quadriceps and hamstrings muscles of children with cerebral palsy (CP) and to show the effects of spasticity in constraining knee velocities during fast gait. DESIGN: A quantitative comparison of neuromuscular and biomechanical performance in patients with CP and controls without CP. SETTING: Movement analysis laboratory within a university clinical referral center. PARTICIPANTS: A convenience sample of 18 ambulatory patients with CP and 11 control subjects without CP. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Spastic threshold velocity recorded from electromyographic response during passive isovelocity knee movement was compared with knee angular velocity during fast walking, Gross Motor Function Measure (GMFM) scores, and Ashworth Scale score. RESULTS: Patients with measurable spasticity showed slower peak knee angular velocity during walking than patients without spasticity (P<.005). A significant correlation existed between spastic threshold velocity and peak knee angular velocity during fast walking (r=.85, P<.001). Spastic threshold velocity correlated significantly with GMFM (r=.58, P<.05) but not with Ashworth score. CONCLUSIONS: The velocity dependency of spasticity can be measured by electromyograph and dynamometer to determine spastic threshold velocity. Spastic threshold velocity correlated with limitations in joint angular velocity during walking and functional performance.

Adolescent↗

PubMed2002

Inhibitory effect of bFGF on endochondral heterotopic ossification.

Basic fibroblast growth factor (bFGF) is reported to stimulate repair of fracture and bony defects in in vivo animal studies. However, most studies performed in vitro demonstrate inhibitory effect of bFGF on cartilage and bone differentiation. To understand the discrepancy observed in in vivo and in vitro studies, we evaluated the effect of bFGF on chondro-osteogenesis initiated by bone matrix powder (MP). MP was implanted in the murine hamstring muscles with or without administration of bFGF. Injection of 1 microg of bFGF markedly reduced the size of heterotopic bone induced by MP, as detected by X-ray. Injection of 10 microg of bFGF completely inhibited ossification and only fibrous tissues were observed at the site of MP implantation. The expressions of alkaline phosphatase and osteocalcin mRNAs, markers for bone differentiation, were completely suppressed by 10 microg of bFGF. These results demonstrate the inhibitory effect of bFGF on endochondral ossification in vivo, implicating a precaution for its use in musculo-skeletal disorders.

Alkaline Phosphatase↗

PubMed1998

[Myositis ossificans circumscripta and sequelae of muscular ischemia. 2 cases].

INTRODUCTION: Non-traumatic myositis ossificans circumscripta is a relatively rare, well defined entity. The pathogenic role of ischemia in its development is discussed. EXEGESIS: We report two cases of myositis ossificans circumscripta that occurred in the hamstring muscle respectively 22 and 35 years after ischemic muscular injury in the same site. Clinical and radiologic informations and follow-up were reexamined, showing that patients are usually young and that the disease is equally distributed between both genders. Though the lesion may develop in various muscle, it is preferentially observed in proximal sites. Most patients have a history of localized pain or tenderness accompanied by swelling of the affected site. Following a 5- to 12-week increase, the soft-tissue mass is less sensitive and better defined. It may also resolve in less than 3 years. CONCLUSION: Results of X rays, computerized tomography, MR imaging and biopsy are reviewed. Histologically, this lesion main feature is peripheral bone maturation within three areas. Mechanisms (traumatic or not) underlying these lesions are unknown. To our knowledge, only one published case would be comparable to ours. Proliferation followed by change in mesenchymal cells leading to heterotopic ossification must be regarded as a consequence of either ischemia or repeated micro-trauma occurring during muscle shortening.

Follow-Up Studies↗

PubMed2000

Passive moment about the hip in straight leg raising.

OBJECTIVE: The purpose of this examine is to study the load-deformation characteristics of the hip in straight leg raising. DESIGN: An experimental study in which passive moment about the hip was determined as a function of hip angle. BACKGROUND: Straight leg raising is widely employed in clinical examination, and there is little information on its mechanical characteristics. METHODS: Fourteen healthy volunteers were recruited for this study. Three trials of straight leg raise tests were performed while subjects lay supine on a plinth that was fitted with load cells. An electrogoniometer was employed to measure hip flexion during the test. Resistive moment at the hip was determined using a dynamic biomechanical model. RESULTS: The present experimental method was shown to be highly reliable. The moment-angle curves of all subjects were shown to follow an exponential function. CONCLUSION: Stiffness and strain energy of posterior hip tissues could be derived from the moment-angle curves. Evaluation of such elastic properties is clinically important as they may be altered with injuries of the tissues. RELEVANCE: Clinically, contracture of hamstring muscles and other posterior hip tissues is evaluated by measuring the available range of hip flexion in straight leg raising. However, this does not provide any information on the elastic properties of the tissues. The present study reports a reliable method of evaluating such properties.

Adult↗

PubMed1998

Development of mustard oil-induced hyperalgesia in rats.

Age-dependent changes in nociceptive responses were investigated using either the electromyogram (EMG) recorded from the hamstring muscle in response to electrical stimulation of the hind foot in spinal transected rats or measurement of the tail-flick (TF) reflex latency in intact rats. The development of hyperalgesia produced by topical application of mustard oil was subsequently studied. In experiments involving EMG recordings, rats were tested from day 2 to day 34 after birth (4-day interval) and as adults. In experiments involving measurement of the TF reflex, rats were tested from day 5 to day 30 after birth (5-day interval) and as adults. It was found that the latency and the duration of an early component of the EMG decreased with an increase in animal age, and was similar to adult animals at approximately 18 days after birth. The thermal tail withdraw threshold was lower in pups in comparison with older rats, and took more than 30 postnatal days to become similar to that of adult rats. Although nociceptive behaviors such as biting, body movement, and vocalization could be produced in intact rats by mustard oil in rats as young as 5 days old, the intensities of these responses were subjectively less than those of adult rats. Mustard oil application enhanced significantly the EMG response to electrical stimulation and the effect increased with increasing age. Similarly, mustard oil applied to a hind leg facilitated the TF reflex (decreased response latency). In both experiments, it took approximately 34-40 postnatal days for mustard oil-produced hyperalgesia to become similar to that of adult rats. These data confirm that nociceptive processing is not mature in the young animal and that a developmental period after birth is required for hyperalgesia-related mechanisms to mature.

Age Factors↗

PubMed1999

Spinal neurokin3 receptors facilitate the nociceptive flexor reflex via a pathway involving nitric oxide.

The present study examined the effects of intrathecal administration of neurokinin3 receptor agonists on the electrically-evoked nociceptive flexor reflex in decerebrate and spinalized adult rats. The reflex was evoked by stimulating the isolated sural nerve at an intensity that activates C fibers and was measured by recording the number of compound potentials in the ipsilateral hamstring muscles. Intrathecal senktide (1-30 nmol), a neurokinin3 receptor agonist, dose-dependently facilitated the reflex reaching a maximum effect of 230% of the baseline reflex at 10 nmol. SR 142801 (60 nmol), a non-peptide neurokinin3 receptor antagonist, blocked facilitation of the reflex induced by 10 nmol senktide, providing further support that the effect of senktide is mediated by neurokinin3 receptors. The intrathecal administration of senktide (10 nmol) did not alter the monosynaptic reflex elicited by stimulating the L5 dorsal root at an intensity that was at the threshold for activating A fibers. This indicates that the senktide-induced facilitation of the nociceptive flexor reflex was not at the level of the motor neuron. Pretreatment with N(G)-nitro-L-arginine methyl ester (30 nmol), a nitric oxide synthase inhibitor, attenuated the effect of senktide, indicating that facilitation of the reflex by senktide is also mediated by the production of nitric oxide. Data from the present work have shown that spinal neurokinin3 receptors facilitate the nociceptive flexor reflex through a pathway that involves interneurons and the production of NO. Therefore, neurokinin3 receptors are likely to be involved in enhancing nociceptive neurotransmission at the level of the spinal cord.

Animals↗

PubMed2004

Estimation of hamstring length at initial contact based on kinematic gait data.

This study proposes a simple estimate of hamstring length at initial contact (LEST) for use when musculoskeletal modelling is not available. The estimate is calculated by using the kinematic curves to measure the excessive flexion (above normal) at the hip and knee at initial contact. The excessive hip flexion is then multiplied by a scaling factor (k) and the excessive knee flexion subtracted from the result. Validation of this estimate was carried out using kinematic gait data from 25 children with cerebral palsy (50 limbs) by comparing the results of the estimate with an equivalent measure derived from musculoskeletal modelling (LTRUE). Very high agreement was found when LTRUE and LEST were compared for the three biarticular hamstring muscles, demonstrated by correlation coefficients of over 0.9. Different k values were tested with a value of 3 giving the best results overall. The estimate is acceptable as a simple 'rule of thumb' for use in clinical practice. It can provide useful additional information to complement the clinical examination and gait assessment results.

Adolescent↗

PubMed2001

Comparison of EMG activity of medial and lateral hamstrings during isometric contractions at various cuff weight loads.

Since both the medial head (MH) and lateral head (LH) of the hamstring muscles contribute to knee flexion, this study investigated whether the relative electrical activity of these heads remained constant with respect to each other or changed during isometric contractions at five different resistance levels. The relative electrical activity of these two heads was determined by comparing their integrated EMG (iEMG). Forty-two volunteers with no history of right lower extremity injury or disease, between the ages of 18 and 35, were studied. Following motor point location, surface electrodes were placed over the MH and LH. Subjects, positioned prone, flexed the knee to 45 degrees using a sawhorse as a tactile cue to help maintain this position. Three recordings, 8 s in length, were taken at each subject's maximum isometric contraction and then using cuff weights of 1, 3, 5, and 7% of their body weight. The average of the three recordings was used in the analysis. During maximum isometric contraction (at 45 degrees of knee flexion), the LH contributes a significantly greater percent of the total iEMG (63.4%) than the MH (P < 0.0001). Furthermore, within the four submaximal levels tested, the LH's contribution was significantly greater than the MH (P < 0.01). During submaximal isometric contractions, the LH percent contribution to total iEMG was less than its contribution during maximal isometric contraction, all P values < 0.005. As a result, during these same submaximal isometric contractions, the MH contribution to total iEMG was greater than its contribution during maximal isometric contraction, all P values < 0.005).

Adolescent↗

PubMed1999

Botulinum toxin for amelioration of knee contracture in Duchenne muscular dystrophy.

An 11-year-old non-ambulant boy with Duchenne muscular dystrophy developed tightness in his left knee flexors, which caused difficulties in standing exercises. Botulinum toxin A (BTX-A) was injected into the medial and lateral hamstring muscles and the range of motion increased by 20 degrees but after 5 months, when the pharmacological effect of BTX-A had vanished, an increase of only 5 degrees in range compared with the initial finding was left. It is concluded that there may be a role for BTX-A in controlling contractures in Duchenne muscular dystrophy.

Botulinum Toxins, Type A↗

PubMed2001

Distinct multi-joint control strategies in spastic diplegia associated with prematurity or Angelman syndrome.

Spastic diplegia is commonly due to periventricular leucomalacia associated with premature birth. It is also a feature of Angelman syndrome (AS), a neurogenetic disorder with developmental delay, absent speech and mirthful behaviour. We studied the kinematics and kinetics of the squatting movement and associated electromyographic (EMG) activities in 20 children with spastic diplegia associated with periventricular leucomalacia (SDPL) or AS and 18 unimpaired children. While movement of normal subjects consisted of vertical translation of most body segments, the movement of SDPL children was operated around the fixed knee with backward shift of the hip, and AS children performed a forward flexion of the trunk over the thigh. Trunk stability was correlated with movement velocity in both pathological groups. In normal subjects, anticipatory EMG pattern consisted of silencing of hamstring muscle tonic activity prior to movement onset. This deactivation was not present in spastic diplegia. In SDPL, anticipatory overactivation of ankle joint actuators was recorded and tonic co-contraction persisted throughout the movement. In AS, rhythmic EMG bursting was seen during the movement. Shoulder, hip and knee trajectories in the sagittal plane showed marked within-group stereotypies in orientation, shape and length. The patterns in both pathological groups were therefore distinctive. We speculate that they reflect corticospinal impairment in SDPL and combined corticospinal and cerebellar dysfunction in AS.

Angelman Syndrome↗

PubMed2002

Australian football: injury profile at the community level.

Successful injury prevention relies on injury surveillance to establish the extent of the problem, to monitor injury patterns and to evaluate prevention strategies. Despite the popularity of participation in Australian football at the community level, few injury surveillance studies have been published describing the pattern of injuries at this level of participation. In contrast, ongoing injury surveillance at the elite-level is well established. Reliance on injury data from the elite-level of Australian football to guide injury prevention at the community level may not be appropriate due to differences across the levels with respect to exposure, fitness and skill level. Therefore, specific injury surveillance at the community level of Australian football is warranted. This study describes the epidemiology of community level Australian football injuries. Injury surveillance was undertaken in five amateur Australian football clubs over the 1999 season. The 320 participating players sustained 421 injuries over the season. The overall rate of injury was 27 injuries per 1000 player hours. Injuries were most commonly sustained at the start of the season and during the second quarter of match participation. Hamstring muscle strains were the most common injury sustained, followed by thigh haematomas and lateral ligament sprains of the ankle. The injury surveillance system used in this study was well accepted by the clubs and provides detailed data for the prioritisation of future injury prevention research at the community level of Australian football.

Adolescent↗

PubMed2002

Identification and characterization of regulatory elements of the human prostatic acid phosphatase promoter.

Human prostatic acid phosphatase (PAcP) is a prostate epithelium-specific differentiation antigen. The cellular form of PAcP functions as a neutral protein-tyrosine phosphatase, and is involved in regulating prostate cell growth. Although some information on the PAcP gene structure has been obtained, little is known regarding the cis- and trans-acting factors that regulate its expression. Due to the biological importance of PAcP, we investigated the regulation of its expression. A region upstream of the PAcP gene from -2899 to +87 base pairs was linked to the coding sequence of the chloramphenicol acetyltransferase (CAT) gene. Sequential deletions of the sequence between -2899 and -205 revealed that, in addition to the basic promoter, the region between -1258 and -779 represents a positive regulatory element. This -1258/-779 fragment could enhance the PAcP promoter activity in PC-3 and DU 145 human prostate cancer cells, but not in non-prostate cancer cells, including WI-38 lung diploid cells, A-431 epidermoid carcinoma cells, and HeLa cervix epitheloid carcinoma cells. Furthermore, this cis-element together with the promoter sequence could drive a high level of expression of green fluorescent protein (GFP) in PC-3 cells, but not in HeLa cells. The prostate-specific expression was further examined by injecting naked plasmid DNA into the prostate and the hamstring muscle of mice. The fluorescence pattern clearly showed that the level of GFP expression is consistently higher in prostate cells than in muscle cells of the intact animal. The data collectively indicate that region between -1258 and -779 is involved in governing the cell type-specific expression of the PAcP gene.

Acid Phosphatase↗

PubMed2002

Testicular-associated immune deviation: flushing of the testicular lymph sinusoids induces immunosuppression and inhibits formation of EAE in SJL mice.

Injection of antigen into the testis has been previously proved to induce systemic tolerance in rats. Testicular-associated immune deviation (TAID) has thus far been induced and studied only in the rat and the present study was planned to study if TAID could be induced in mice as well. In addition, it was studied if TAID is organ-specific. Mouse spinal cord homogenate (MSCH), as well as phosphate-buffered saline (PBS), was injected into the testes of SJL and BALB/c male mice before the induction of experimental allergic encephalomyelitis into the animals. The control animals received MSCH intramuscularly into the hamstring muscles. The animals were followed and graded daily for symptoms attending the next 30 days. In the SJL strain, mice treated with an intratesticular (i.t.) MSCH injection prior to the induction of experimental autoimmune encephalomyelitis (EAE) had the shortest duration of symptoms and the longest time to the onset of the first symptoms. In addition, the mice injected i.t. with PBS had as mild symptoms as those injected with MSCH. There was a statistically significant difference, however, between the groups injected either with MSCH or PBS intratesticularly. In general, mice treated with an intramuscular injection of MSCH got sick first, and had the most severe symptoms for the longest duration of time. In the case of the BALB/c mice, there were no statistical differences between the groups investigated. It is concluded that TAID is a testis- and strain-specific phenomenon in the mouse, and not specific to the rat. In addition, i.t. injection of PBS is just as effective in creating tolerance against EAE as i.t. injection of MSCH in the SJL mice.

Animals↗

PubMed2003

Failed regrowth of the harvested semitendinosus tendon: a rare complication of tendon harvest after anterior cruciate ligament reconstruction.

Harvested hamstring tendons were recently shown to possess the ability to regrow and regain their function in flexing the knee joint. In this study, we report a case of failed regrowth of previously harvested semitendinosus tendon to its original insertion site in a 24-year-old professional soccer player. The disturbance resulted in the formation of a clearly visible Popeye-type muscular prominence in the proximal thigh and a notable gap in the midthigh distal to the muscular prominence in knee flexion. Furthermore, 6 months after surgery, in the second full-speed soccer practice, the patient experienced a sudden sharp pain in his hamstring muscles, which was later diagnosed as being from a strain of the semitendinosus muscle.

Adult↗

PubMed2006

Specific adaptations of neuromuscular control and knee joint stiffness following sensorimotor training.

The aim of this study was to examine how fixations of the ankle joint during sensorimotor training (SMT) influence adaptations in mechanical stiffness and neuromuscular control of the knee joint. Sixty-three healthy subjects were randomly assigned to three training groups that differed in their degree of ankle joint fixation, which was either barefooted, with an ankle brace or with a ski boot. Mechanical knee joint stiffness and reflex control of m. vastus medialis, m. vastus lateralis, m. biceps femoris, and m. semitendinosus were tested during force controlled anterior tibial displacements. This force was applied as both a fast and a slow stimulus. After the training period the group that trained barefooted showed an increase in mechanical stiffness of the knee joint from 79 +/- 21 (Mean +/- SD) N/mm to 110 +/- 38 N/mm (p < 0.05) in the fast stimulus. The training group that trained with ski boots was able to improve knee joint stiffness from 67 +/- 26 N/mm to 96 +/- 47 N/mm (p < 0.05) in the slow stimulus. These improvements correspond with an enhanced activity of the hamstring muscles (m. biceps femoris and m. semitendinosus). From a more functional point of view, specific adaptations due to the fixation of the ankle joint may be helpful in the prevention and rehabilitation of knee joint injuries.

Adaptation, Physiological↗

PubMed1999

Health-related fitness test battery for middle-aged adults: associations with physical activity patterns.

To evaluate the validity of a health-related fitness (HRFI) test battery with respect to physical activity (PA), we studied how PA patterns of adults are related to different components of HRFI with special interest in musculoskeletal and motor fitness. Subjects (n = 498) were middle-aged (37-57 years) men and women, evenly selected from five age cohorts of a representative population sample. PA was assessed with a questionnaire and classified into three PA groups. Fitness assessment included 9 simple field tests. The odds ratio of low fitness (least fit 40 %) of the measured dimension of HRFI for three PA groups with reference to inactive group were analysed. All PA groups were strongly related to Walk Test results in both genders, and to BMI in women. Muscular type exercise was associated with modified push-ups strength and static back extension endurance in both genders, and with one-leg standing balance in women. One-leg squat for leg strength, jump-and-reach for leg power, trunk side-bending flexibility and hamstring muscle extensibility tests were not associated with PA. Five of the nine fitness tests demonstrated plausible associations with PA patterns among adults suggesting activity-related validity. An exercise intervention study is needed to evaluate the sensitivity of the tests to fitness changes.

Adult↗