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PubMed1988

Convergent effects from vestibulospinal tract and primary cutaneous afferent fibers on motoneurons to proximal lower limb flexor and extensor muscles in humans.

In human subjects, the latency and magnitude of cutaneomuscular test reflexes, evoked by stimulation of the sural nerve in the contralateral and ipsilateral quadricep and hamstring muscles, were investigated during static tilts in the pitch axis. The ANOVA demonstrated a highly significant, tilt-dependent modulation of the magnitude of the test reflex for the initial phase of both ipsilateral quadriceps and ipsilateral hamstrings. These results are consistent with results from a similar study on human ankle muscles and provide further evidence that the tilt-dependence of these cutaneomuscular reflexes originates from activity in the otolith receptors.

Afferent Pathways↗
PubMed1998

The measurement of muscle stiffness in anterior cruciate injuries -- an experiment revisited.

OBJECTIVE: To investigate the reported changes in angular stiffness of the knee due to the hamstrings muscles in the anterior cruciate ligament (ACL) deficient knee. DESIGN: The flexors of the knee were modelled as springs and the model tested on patients and controls. BACKGROUND: A previous study had used a similar model but showed no difference between an ACL deficient and an uninjured knee. METHODS: A modification of a recently described method for measuring the stiffness of the hamstrings was used. ACL deficient patients were investigated and also normal controls. RESULTS: We found that stiffness not only varied between patients, but also between legs, with the injured leg having significantly stiffer flexor muscles (P < 0.001). We also showed that the stiffness of the knee due to the flexors is the same in normal subjects as that in the uninjured contralateral knee of the ACL injured patient. CONCLUSIONS: The measurement of the stiffness of the hamstrings following ACL injury may be a valid method of assessing patients with such injuries. Further investigation is required.

Journal Article↗
PubMed2003

IGF-I gene transfer by electroporation promotes regeneration in a muscle injury model.

The goal of this study was to determine whether insulin-like growth factor-I (IGF-I) gene delivery by electroporation promotes repair after muscle injury. An injury-repair model was created using mice in which a hamstring muscle was cut and sutured. A total of 50 microg of IGF-I DNA or green fluorescent protein (GFP) DNA (both in pCAGGS) was injected into the lesion and introduced into muscle cells by electrostimulation using an electric pulse generator. The number of regenerating muscle fibers in the IGF-I DNA group was significantly more than that in the GFP DNA group at 2 weeks after injection. The diameter of regenerating muscle fibers from the IGF-I DNA group was larger than that of the GFP DNA group at 4 weeks after injection. There was no significant difference in the serum IGF-I concentration between the IGF-I DNA group and the GFP DNA group at 1, 2, and 4 weeks after injection. However, muscle IGF-I concentration in the IGF-I DNA injection group was significantly greater than that in the GFP DNA injection group at 2 weeks after injection. These results demonstrated that the effects of enhanced IGF-I production were local and limited to the injected area. The ratio (injected/uninjected; intact) of the amplitude of compound muscle action potentials (CMAP) in the IGF-I DNA injection group was greater than that in the GFP DNA injection group at 4 weeks after injection and of the control group. In conclusion, IGF-I gene transfer by electroporation proved to be a simple, safe, inexpensive, and effective method to promote the regeneration of injured muscles in our injury model.

Animals↗
PubMed2000

Adaptation of neuromuscular synergies during intentional constraints of space-time relationships in human gait.

Tight frequency-to-amplitude relationships are observed in spontaneous human steady gait. They can be modified, if required; that flexibility forms a fundamental basis of the intentional adaptive capabilities of locomotion. In the present experiments, the processes underlying that flexibility were investigated at both the level of joint kinematics and the level of neuromuscular synergies. Subjects (N = 4) walked at the same speed either with a preferred or a nonpreferred frequency-to-amplitude relationship (i.e., constrained, short steps at a high frequency [COS condition] or constrained, long steps at a low frequency [COL condition]); their swing and stance phases were separately analyzed. In the COS condition, increases in EMG activity were specifically required during the swing phase. In the COL condition, several muscles required increases in EMG activity during the stance phase, but decreases of the hamstring muscles were needed during the swing phase. Whereas, in preferred walking, modification of the frequency affects the EMG patterns globally (the gain increasing with the frequency in both the stance and swing phases), the present results show that changing the frequency in a constrained manner either affects the swing phase specifically or affects both phases, but in the opposite direction. That finding indicates that a separate control is needed in both the swing and the stance phases.

Adult↗
PubMed1988

Electrical stimulation versus voluntary exercise in strengthening thigh musculature after anterior cruciate ligament surgery.

Twenty patients who had undergone anterior cruciate ligament reconstructive surgery were placed randomly and independently in an Electrical Stimulation Group (n = 10) or Voluntary Exercise Group (n = 10) to compare the effectiveness of these two muscle-strengthening protocols. Patients in both groups used simultaneous contraction of quadriceps femoris and hamstring muscles during a training regimen that consisted of either voluntary exercise or electrical stimulation trials five days a week for a three-week period within the first six postoperative weeks. After patients completed the training regimen, bilateral maximal isometric measurements of gravity-corrected knee extension and flexion torque were obtained for both groups and percentages were calculated. Results showed that patients in the Electrical Stimulation Group finished the three-week training regimen with higher percentages of both extension and flexion torque when compared with patients in the Voluntary Exercise Group (extension: t = 4.35, p less than .05; flexion; t = 6.64, p less than .05). These results indicate that patients in an electrical stimulation regimen can achieve higher individual thigh musculature strength gains than patients in a voluntary exercise regimen when simultaneous contraction of thigh muscles is prescribed during an early phase of postoperative rehabilitation.

Adult↗
PubMed2006

Botulinum toxin A injection for spasticity in diplegic-type cerebral palsy.

Botulinum toxin type A can be both safe and effective in relieving spasticity in pediatric patients with cerebral palsy. In our prospective study, we evaluated the functional effect of botulinum toxin A in spastic diplegic-type cerebral palsy. Patients were examined on enrollment and at 1, 3, and 6 months after injection. Passive dorsiflexion of the ankle joint was measured using a goniometer as an angle of possible maximal dorsiflexion with the knee extended and flexed. Spasticity was graded using the Modified Ashworth Scale. Selective motor control at the ankle was assessed, and observational gait analysis was done. The functional status of the patients was determined by using the gross motor classification system. Botulinum toxin A was injected into the gastrocnemius muscle in all patients, and in four patients with concomitant jump knee gait, a hamstring muscle injection was added. Fourteen patients were included in the study. The mean age was 58.81 +/- 15.34 months. Following injection, spasticity was clinically decreased and statistically significant improvement was noticed in all clinical parameters after 1, 3, and 6 months of injection. The improvement in the clinical parameters decreased after 6 months but not to the baseline. One patient was Level II, four patients were Level III, and six patients were Level IV according to the Gross Motor Function Classification System at baseline. Improvement in the gross motor classification system is continued after 6 months in 12 children. The main goal of spasticity treatment in cerebral palsy is functional improvement. In our study, most of our patients had functional improvement according to the gross motor function classification system and did not change at 6 months.

Botulinum Toxins, Type A↗
PubMed1994

Influence of hamstring length on the standing position and flexion range of motion of the pelvic angle, lumbar angle, and thoracic angle.

Hamstring muscle length may be associated with specific pelvic and trunk postures, but the influence of hamstring length on trunk postures is not well documented. The purposes of this study were to examine the influence of hamstring length on 1) the pelvic angle, lumbar angle, and thoracic angle in standing; and 2) the flexion ranges of motion of the pelvic angle, lumbar angle, and thoracic angle during the toe-touch test. Surface platform pointers over bony landmarks and photography were used to examine the pelvic and trunk angles and ranges of motion of 10 men with short hamstrings, 10 men with medium hamstrings, and 10 men with long hamstrings while standing and after assuming the toe-touch position. Separate one-way analyses of variance detected no significant differences among groups for the three angles in standing. Significant differences were detected among groups for the three angles in the toe-touch position and the flexion ranges of motion during the toe-touch test (p < 0.05). Short hamstrings were associated with decreased flexion range of motion of the pelvic angle and lumbar angle and increased flexion range of motion of the thoracic angle. Therapeutic interventions should be considered in light of the influences of hamstring length on the flexion range of motion of the pelvic angle, lumbar angle, and thoracic. angle.

Adult↗
PubMed2000

Contralateral movement and extensor force generation alter flexion phase muscle coordination in pedaling.

The importance of bilateral sensorimotor signals in coordination of locomotion has been demonstrated in animals but is difficult to ascertain in humans due to confounding effects of mechanical transmission of forces between the legs (i.e., mechanical interleg coupling). In a previous pedaling study, by eliminating mechanical interleg coupling, we showed that muscle coordination of a unipedal task can be shaped by interlimb sensorimotor pathways. Interlimb neural pathways were shown to alter pedaling coordination as subjects pedaling unilaterally exhibited increased flexion-phase muscle activity compared with bilateral pedaling even though the task mechanics performed by the pedaling leg(s) in the unilateral and bilateral pedaling tasks were identical. To further examine the relationship between contralateral sensorimotor state and ipsilateral flexion-phase muscle coordination during pedaling, subjects in this study pedaled with one leg while the contralateral leg either generated an extensor force or relaxed as a servomotor either held that leg stationary or moved it in antiphase with the pedaling leg. In the presence of contralateral extensor force generation, muscle activity in the pedaling leg during limb flexion was reduced. Integrated electromyographic activity of the pedaling-leg hamstring muscles (biceps femoris and semimembranosus) during flexion decreased by 25-30%, regardless of either the amplitude of force generated by the nonpedaling leg or whether the leg was stationary or moving. In contrast, rectus femoris and tibialis anterior activity during flexion decreased only when the contralateral leg generated high rhythmic force concomitant with leg movement. The results are consistent with a contralateral feedforward mechanism triggering flexion-phase hamstrings activity and a contralateral feedback mechanism modulating rectus femoris and tibialis anterior activity during flexion. Because only muscles that contribute to flexion as a secondary function were observed, it is impossible to know whether the modulatory effect also acts on primary, unifunctional, limb flexors or is specific to multifunctional muscles contributing to flexion. The influence of contralateral extensor-phase sensorimotor signals on ipsilateral flexion may reflect bilateral coupling of gain control mechanisms. More generally, these interlimb neural mechanisms may coordinate activity between muscles that perform antagonistic functions on opposite sides of the body. Because pedaling and walking share biomechanical and neuronal control features, these mechanisms may be operational in walking as well as pedaling.

Adult↗
PubMed2002

[Quadriceps and hamstring strength after anterior cruciate ligament rupture treated operatively with Leeds-Keio prosthesis and without surgery].

69 patients with the ACL rupture: 40 non-operated, without functional knee instability, and 29 after the ACL reconstruction using Leeds-Keio prosthesis due to knee instability have been evaluated. Isometric dynamometric examination of the quadriceps and hamstring muscles was performed. The mean strength deficit in non-operated group was: quadriceps--18.48%, hamstring--7.19%, in operated group was: quadriceps--11.87%, hamstring--10.30%. The higher strength deficit of the quadriceps and lower of the hamstring in non-operated patients may be the sign of an adaptational mechanism to the ACL deficiency. No statistical correlation between the strength deficit and the deficit of the thigh circumference 10 cm above the patella was found.

Adult↗
PubMed1996

Sport stretching: effect on passive muscle stiffness of short hamstrings.

OBJECTIVE: To evaluate the effects of one 10-minute stretch on muscle stiffness in subjects with short hamstrings. DESIGN: Randomized control trial. SETTING: Laboratory for human movement sciences in the department of rehabilitation of a university hospital. SUBJECTS: Sixteen students from the Department of Human Movement Sciences participated with informed consent in the experiment. Subjects were limited to men and women without a history of neurological and orthopedic disorders. To select subjects with short hamstrings, the finger-ground distance had to be greater than 0cm (unable to touch the floor when bending forward) and the manual leg lifting was not to exceed 80 degrees. One group of 10 subjects performed static stretching exercises during 10 minutes interspersed with relaxing, whereas the untreated group of 6 subjects was used as a control. MAIN OUTCOME MEASURES: The instrumental straight-leg-raising set-up enables the measurement of the force needed to lift the leg, range of motion (ROM), pelvic-femoral angle, and the electromyogram of the hamstrings. These variables provide information about the stiffness, elongation, and state of activity of the hamstring muscles. RESULTS. One 10-minute sport stretch resulted in a significant increase in passive muscle moment, ROM, and elongation of the hamstrings. There was no significant change in the course of the passive muscle stiffness curve with respect to the prestretch stiffness curve. CONCLUSIONS: One session of static stretching does not influence the course of the passive muscle stiffness curve. The increased ROM, i.e., the extensibility of the hamstrings, results from an increase in the stretch tolerance.

Adult↗
PubMed1981

Hamstring tightness and Scheuermann's disease a pilot study.

The lateral radiographs of the dorsal spines of 20 patients presenting with mainly low back pain are studied. These patients had clinically evident loss of flexion in the low dorsal spine and very tight hamstring muscles. 85% of them showed definite evidence of previous Scheuermann's Disease. The possibility that tight hamstrings may be an important factor in the aetiology of this disease is discussed, and a further large scale study is proposed.

Adolescent↗
PubMed1996

[Reversed musculus biceps femoris flap for covering a defect of the distal thigh].

We report the case of a 30-year-old female patient, who had suffered a grade III open femur fracture in a motor vehicle accident 14 weeks prior to being transferred to the trauma department of the University Hospital in Bonn. Upon admission to our unit, posttraumatic osteitis, an unstable fracture following compression plating, and a soft tissue defect of the anterolateral distal thigh were discovered. Following removal of the hardware and stabilization of the fracture with external fixation, the infection was brought under control. Because the patient refused the time-consuming segmental transport utilizing the callus distraction technique, local muscle transfer and shortening of the femur were carried out. The most lateral of the hamstring muscles, the biceps femoris, was used as a distally based muscle flap utilizing a delay technique. With the help of a reversed biceps femoris flap, the soft tissue defect was closed, the infection subsided and the fracture healed. The surgical technique is outlined.

Adult↗
PubMed1996

A mechanism for altered flexibility in human skeletal muscle.

1. We investigated the effect of a long-term stretching regimen on the tissue properties and stretch tolerance of human skeletal muscle. 2. Resistance to stretch was measured as torque (in N m) offered by the hamstring muscle group during passive knee extension while electromyographic (EMG) activity, knee joint angle and velocity were continuously monitored during a standardized stretch manoeuvre. Seven healthy subjects were tested before and after a 3 week training period using two separate protocols. Protocol 1 consisted of a slow stretch at 0.087 rad s-1 to a predetermined angle followed by a 90 s holding phase. Subjects were brought to the same angle before and after the training period. Protocol 2 was a similar stretch, but continued to the point of pain. 3. During protocol 1 the torque rose during the stretch and then declined during the holding phase. EMG activity was small and did not change significantly during the protocol. No significant differences in stiffness, energy and peak torque about the knee joint were seen as a result of the training. During protocol 2 the angle to which the knee could be extended was significantly increased as a result of the training. This was accompanied by a comparable increase in peak torque and energy. EMG activity was small and not affected by training. 4. It is concluded that reflex EMG activity does not limit the range of movement during slow stretches and that the increased range of motion achieved from training is a consequence of increased stretch tolerance on the part of the subject rather than a change in the mechanical or viscoelastic properties of the muscle.

Adult↗
PubMedDate not supplied

Longitudinal effects of anterior cruciate ligament injury and patellar tendon autograft reconstruction on neuromuscular performance.

We examined persons after anterior cruciate ligament injury and for 1.5 years after anterior cruciate ligament reconstruction to analyze changes in anterior knee laxity, lower extremity muscle strength, endurance, and several parameters of neuromuscular function. Sixteen men and nine women (average age, 23.8 years) were evaluated preoperatively, then underwent intraarticular autogenous patellar tendon anterior cruciate ligament reconstruction by the same surgeon and were evaluated at 6, 12, and 18 months postoperatively. Muscle strength was measured isokinetically and neuromuscular function was quantified with simultaneous anterior tibial translation and surface electromyography tests. Forty subjects (26 men and 14 women; average age, 23.5 years) with no known knee abnormalities served as the control group. Subjective questionnaire results showed that by 18 months postoperatively, 20 subjects (80%) believed they had regained their preoperative levels of function. Unfortunately, muscle function in most subjects had not returned to normal. At 12 to 18 months postoperatively, when knee rehabilitation was terminated, significant deficiencies in muscle performance persisted in most patients. Interestingly, in this group of stable knees, quadriceps and hamstring muscle reaction times appeared to be the best objective indicators of subjective knee function.

Adolescent↗
PubMed1985

[Results of muscular x-ray computed tomography in 145 cases of neuromuscular disease].

CT Scan examination in 145 cases of neuromuscular diseases yielded the following results: Diagnosis between myogenic and neurogenic process is inconstant and cannot be considered as absolute. In myogenic diseases the X ray density of muscle is early decreased with a preservation of muscle outline. In neurogenic diseases muscle volume is early decreased. Coexistence of atrophic and hypertrophic muscles indicates primarily muscle disease. Some patterns of involvement appear to be frequent. In Duchenne's dystrophy a contrast exists between atrophic "empty" or hypertrophic muscles during the ambulatory period and "ghostly" muscles during the terminal period. In facio-scapulo-humeral muscular dystrophy, tibialis anterior and hamstring muscles have often a decreased density and psoas muscles are normal or hypertrophic. In myotonic dystrophy a hypodense perifemoral crescent is frequently observed. Diagnosis between limb-girdle myopathy ("empty" muscles with preserved limits, hypertrophic muscles, hypodense gastrocnemius medialis muscles) and chronic spinal amyotrophy (irregular and atrophic muscles without selective involvement and hypertrophic muscles) is tentatively proposed but is not considered to be clear-cut. Muscle involvement has an asymmetric distribution in amyotrophic lateral sclerosis and is rather symmetric in peripheral neuropathies.

Adolescent↗
PubMed2001

The effect of upper-limb motion on lower-limb muscle synchrony. Implications for anterior cruciate ligament injury.

BACKGROUND: A high prevalence of rupture of the anterior cruciate ligament is associated with activities that incorporate both abrupt deceleration and catching a ball. In the present study, we examined whether the upper-limb motion involved in catching a ball affected the synchrony of the lower-limb muscles during tasks known to stress the anterior cruciate ligament-namely, abrupt decelerative landings. METHODS: Seven male and eleven female subjects decelerated abruptly to land in single-limb stance after catching a chest-height pass and after no catching. Ground-reaction force and electromyographic data for six lower-limb muscles were sampled while the subjects' landing technique was filmed. The joint-reaction forces and the sagittal planar net moments for the knee then were calculated to derive the tibiofemoral shear forces. The muscle onsets and peak muscle activities were temporally analyzed with respect to the time of initial foot-ground contact, the peak resultant ground-reaction force, and the peak tibiofemoral shear force. RESULTS: When catching a pass, the subjects demonstrated significantly (p < 0.05) earlier rectus femoris onset relative to the timing of the initial foot-ground contact and of the peak tibiofemoral shear force, and they showed delayed biceps femoris onset relative to the timing of the peak tibiofemoral shear force compared with the findings in the trials without catching. CONCLUSIONS: We concluded that catching a ball during an abrupt landing could increase the potential for an anterior cruciate ligament injury by limiting the time available for the hamstring muscles to generate posterior tibial-drawer force before the onset of the quadriceps-induced anterior tibial translation. CLINICAL RELEVANCE: The integrity of the anterior cruciate ligament during landing relies on the proper coordination of the lower-limb muscles, particularly the quadriceps and the hamstrings. The present study demonstrated that motion of the upper-limbs may interfere with recruitment of these muscles, thereby predisposing the anterior cruciate ligament to injury.

Adult↗
PubMed1999

Reactive muscle firing of anterior cruciate ligament-injured females during functional activities.

OBJECTIVE: The high incidence of noncontact anterior cruciate ligament (ACL) injuries in females has attracted research to investigate the capacity of muscles to reflexively protect the knee joint from capsuloligamentous injury. Numerous reflex pathways link mechanoreceptors in the ACL with contractile fibers in the quadriceps and hamstring muscles. Loads placed on the ACL modify reactive muscle activity through the feed-back process of neuromuscular control and are critical for dynamic muscular stabilization. Noncontact ACL injuries may be the result of aberrations in reactive muscle firing patterns. Therefore, compensatory muscle activation strategies must be employed if functional stability is to be restored after injury or surgical reconstruction. The purpose of our study was to compare the amplitude of reactive muscle activity in females with ACL-deficient (ACLD), ACL-reconstructed (ACLR), and control knees during functional activities. DESIGN AND SETTING: Female volunteer subjects were stratified into groups based on the status of their ACLs. Each subject performed 4 functional activities, bilaterally, during a single test session. SUBJECTS: Twenty-four female subjects participated in this study (ACLD = 6, ACLR = 12, control = 6). MEASUREMENTS: Integrated electromyographic (IEMG) data were collected with surface electrodes from the vastus medialis, vastus lateralis, medial hamstring, and lateral hamstring during downhill walking (15 degrees , 0.92 m/s), level running (2.08 m/s), and hopping and landing from a jump (20.3 cm). IEMG was normalized to the mean amplitude of 3 to 6 consecutive test repetitions. The mean area and peak IEMG of a 250-millisecond period after ground contact was used to represent reactive muscle activity. Side-to-side differences were determined using dependent t tests, and group differences were determined using a one-way analysis of variance. RESULTS: During running, the ACLD group demonstrated significantly greater area and peak IEMG activity in the medial hamstring in comparison with the ACLR group and greater peak activity in the lateral hamstring when compared with the control group. The ACLD group also demonstrated greater peak activity in the vastus medialis and a smaller area of IEMG activity in the lateral hamstring than the control group during running. During landing, the ACLD group demonstrated significantly less area of IEMG activity in the vastus lateralis when compared with the control group. No significant differences were identified between the ACLR and control groups, nor were side-to side differences revealed. CONCLUSIONS: Our results suggest that adaptations occur in the reactive muscle activity of ACLD females during functional activities. Strategies to minimize the anterior tibial translation in response to joint loading included increased hamstring activity and quadriceps inhibition. The reactive muscle activity exhibited in ACLD subjects is presumably an attempt to regain functional stability through the dynamic restraint mechanism. The absence of side-to-side differences suggests that these adaptations occur bilaterally after ACL injury.

Journal Article↗