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At least 343 records · Page 19Linked to original sources

PubMed1992

Viscoelastic stress relaxation in human skeletal muscle.

Viscoelastic stress relaxation refers to the decrease in tensile stress over time that occurs when a body under tensile stress is held at a fixed length. The purpose of this study was to demonstrate viscoelastic stress relaxation in human skeletal muscle. Resistance to stretch (tensile force), hip flexion range of motion (ROM), and reflex contractile activity (IEMG) of the hamstring muscle group were measured during a passive straight leg raise. The testing protocol involved a first stretch to the maximum tolerated ROM with the lower extremity held at that point for 45 s (test 1). All 15 subjects tested (9 men, 6 women) had a stretch induced EMG response. The onset of a sustained EMG response occurred at a specific hip flexion angle in 10 subjects. These 10 subjects (6 men, 4 women) underwent a second straight leg raise stretch (test 2) to a ROM 5 degrees below the ROM at which the onset of EMG activity occurred in test 1. The stretch was held at this hip flexion angle for 45 s. There was a significant decrease in force at final ROM during the 45 s in test 1 (11.35 +/- 1.75 N, P < 0.0001) and in test 2 (4.2 +/- 1.55 N, P < 0.05). The percent decrease from the force at the respective final ROM was not significantly different between the tests (14.4 +/- 2.2% in test 1 and 13 +/- 2.3% in test 2). In test 1 there was a significant decrease over time in IEMG of 59.71 +/- 16.01 microV.s (P < 0.01) which was not significantly correlated to the decrease in force.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1986

Below-knee amputation: a comparison of the effect of the SACH foot and single axis foot on electromyographic patterns during locomotion.

The purpose of this investigation was to measure the effect of two terminal prosthetic components, the SACH foot and the single axis foot, on the locomotion patterns of unilateral below-knee amputees. The ten subjects who participated in the study were evaluated on two occasions, once following prescription of a PTB prosthesis and one terminal device and once following its replacement with the second device. The two devices were allocated alternately at the time of prosthetic prescription to ensure that five of the subjects used the SACH foot initially and five used the single axis foot. The electromyographic activity of the vastus lateralis and medial hamstrings was recorded bilaterally during gait using Beckman surface electrodes. The EMG signals were full wave rectified and low pass filtered to obtain the linear envelope. Pressure sensitive foot-switches were used to correlate the EMG signals with components of the gait cycle. The pattern of quadriceps and hamstring muscle activity of the contralateral limb was similar to that reported for normal individuals and was unaffected by changing the terminal device on the prosthetic limb. The pattern of quadriceps and hamstring activity of the prosthetic limb differed from that of the contralateral limb and was influenced by the change in terminal device. With both devices the muscles were active for a greater percentage of the stance phase when compared to the contralateral limb. With the SACH foot attachment there appeared to be more contraction of the quadriceps and hamstrings during the mid stance phase of gait.

Adult↗

PubMed1984

Isokinetic muscle imbalance and knee-joint injuries. A prospective blind study.

One hundred and seventy-two randomly selected high-school football players underwent pre-season isokinetic muscle-testing to determine if there was any relationship between an imbalance in thigh-muscle function and the occurrence of knee injuries. Strength, power, power-endurance, and time to maximum tension were measured for the quadriceps and hamstring muscle groups for both lower extremities of each athlete. The resulting values were utilized to see if a difference of 10 per cent or more between the right and left extremities or between the mean and actual hamstring-to-quadriceps ratio of the individual extremity would result in more knee injuries. No such relationship was found.

Adolescent↗

PubMedDate not supplied

Effects of eccentric versus concentric training on thigh muscle strength and EMG.

The purpose of this study was to compare pure eccentric and concentric strength training regarding possible specific effects of muscle action type on neuromuscular parameters, such as a decreased inhibition during maximal voluntary eccentric actions. Two groups of young healthy adult men performed 10 weeks of either eccentric or concentric unilateral isokinetic knee extensor training at 90 degrees.s(-1), 4 sets of 10 maximal efforts, 3 days a week. Knee extensor torque and surface EMG from the quadriceps and hamstring muscle groups were collected and quantified in a window between 30 and 70 degrees knee angle (range of motion 90-5 degrees ) during maximal voluntary eccentric and concentric knee extensor actions at 30, 90, and 270 degrees.s(-1). Changes in strength of the trained legs revealed more signs of specificity related to velocity and contraction type after eccentric than concentric training. No major training effects were present in eccentric to concentric ratios of agonist EMG or in relative antagonist (hamstring) activation. Thus, for the trained leg, the muscle action type and speed specific changes in maximal voluntary eccentric strength could not be related to any effects on neural mechanisms, such as a selective increase in muscle activation during eccentric actions. Interestingly, with both types of training there were specific cross-education effects, that is, action type and velocity specific increases in strength occurred in the contralateral, untrained, leg, accompanied by a specific increase in eccentric to concentric EMG ratio after eccentric training.

Adaptation, Physiological↗

PubMed1986

Regional sciatic nerve and muscle blood flow in conscious and anesthetized rats.

The regulation of peripheral nerve blood flow is incompletely understood. Regional blood flow in the rat sciatic nerve (NBF) and hamstring muscle (MBF) was measured in both conscious and anesthetized normal rats and in rats that had undergone surgical exposure of one sciatic nerve just prior to measurement. The distribution of [14C]butanol following its bolus intravenous injection was used to determine the flows in a modification of the "indicator fractionation" technique. NBF in normal rats was similar in limb pairs and was unaffected by pentobarbital sodium anesthesia. The pooled value was 12.5 +/- 1.1 ml X min-1 X 100 g-1. NBF was unaffected by sham operation in the conscious rats but was doubled in operated limbs of anesthetized rats (P less than 0.001). MBF in conscious normal rats was five times that measured during anesthesia. As in NBF, sham operation significantly increased MBF only in anesthetized rats (P less than 0.01). [14C]butanol distribution is a sensitive indicator of NBF and MBF. Mere surgical exposure of the nerve significantly increases NBF and MBF in anesthetized, but not in conscious rats.

Anesthesia↗

PubMed1996

Fibroblast growth factor-induced motor end plate regeneration in atrophic muscle.

OBJECTIVE: To determine whether fibroblast growth factor 1 implanted with viable nerve into atrophic muscle will stimulate formation of functional, acetylcholine producing motor end plates. DESIGN: Twelve male Lewis rats underwent predenervation of the hamstring muscle 8 weeks before implantation of the nerve at a site distant from the original motor end plate. Six animals underwent implantation of the tagged nerve ending into atrophic muscle with 50 microgram of fibroblast growth factor 1 in a fibrin adhesive carrier (group 1). Three animals underwent implantation with nerve, fibrin adhesive, and no fibroblast growth factor 1 (group 2); and three animals underwent implantation with fibroblast growth factor 1 and fibrin adhesive with no nerve (group 3). Animals were killed 9 weeks after implantation and nerve and muscle specimens were harvested. MAIN OUTCOME MEASURES: Histoenzymologic methods for acetylcholinesterase and silver impregnation of nerve fibers were performed 9 weeks after fibroblast growth factor 1-fibrin adhesive implantation. Variables included the number of motor end plates per highpower field and motor end plate length. RESULTS: Robust axonal sprouting and formation of multiple motor end plates were found arborized in serial fashion equidistant around the implanted nerve ending. Rare extrasynaptic staining occurred. End plate lengths were significantly shorter in the fibroblast growth factor 1-treated muscles (group 1) than in the specimens without fibroblast growth factor 1 (group 2) (31.2 vs 58.5 micron; P>001, paired t test). The arborization of motor end plates, rare extrasynaptic staining, and shorter end plate lengths seen in group 1 were all consistent with mature motor end plates. Controls (group 3) displayed limited motor end plate formation and extensive extrasynaptic staining typical of denervation. CONCLUSION: This study presents encouraging evidence that fibroblast growth factor 1 with fibrin adhesive carrier can facilitate the reinnervation of atrophied muscle by enhancing the formation or revitalization of motor end plates. Future studies will address muscle function and use of different carrier materials.

Animals↗

PubMed1993

Baseball batting. An electromyographic study.

The muscle firing pattern in 12 muscles throughout the lower extremity, trunk, and upper extremity during the batting swing is described in this study. The two hamstring muscles studied and the gluteal muscle had a similar pattern of high muscle activity during pre-swing and early swing, and then rapidly diminished. The vastus medialis demonstrated peak activity between 95 and 110% maximum muscle test (MMT) throughout the swing phases and follow-through. The erector spinae demonstrated activity from 85 to 185% MMT during the swing phases. The abdominal obliques showed greater than 100% MMT during the swing phases and follow-through. The supraspinatus and serratus anterior showed relatively low muscle activity (less than 40% MMT). These results show that batting is a sequence of coordinated muscle activity, beginning with the hip, followed by the trunk, and terminating with the arms. Power in the swing is initiated in the hip, and therefore exercises that emphasize such strength development are indicated. The maintained, high muscle activity in the trunk muscles indicates a need for back and abdominal stabilization and rotation exercises. The relatively low level of activity in the four scapulohumeral muscles tested indicated that emphasis should be placed on the trunk and hip muscles for a batter's strengthening program.

Abdominal Muscles↗

PubMed2002

Effects of two electrical stimulation frequencies in thigh muscle after knee surgery.

The purpose of this study was to compare the effects of two protocols of electrical stimulation combined with voluntary contractions on the recovery of thigh muscles after anterior cruciate ligament (ACL) surgery. Ten sportsmen with a mean age of 26 yrs were randomly assigned into two groups: a 80 Hz stimulated group (5 patients) and a 20 Hz stimulated group (5 patients). All patients received electrical stimulation of the quadriceps femoris, five days a week, for 12 weeks, and had a standard program of voluntary contractions. Muscle and fat volumes of the thigh were assessed using MRI before surgery and after 12 weeks of rehabilitation. Quadriceps and hamstring muscle strength were evaluated by isokinetic measurements. Twelve weeks after surgery, the quadriceps peak torque deficit in the operated limb with respect to the non operated limb at 180 degrees /s and 240 degrees /s was significantly (p < 0.05) less in the 20 Hz group than in the 80 Hz group. This difference was not confirmed when comparing the pre-surgery quadriceps peak torque of the operated limb with the post-surgery one. Subcutaneous fat volume was increased for the two groups at the post-surgery test. This increase was significantly (p < 0.05) greater for the 80 Hz group. Thigh muscle volume deficit was not significantly different between the two groups.

Adipose Tissue↗

PubMed2004

Magnetic resonance imaging of muscle in nemaline myopathy.

We report muscle MRI findings of 10 patients from 8 families with nemaline myopathy. Patients with involvement of the nebulin (NEB) gene showed a consistent pattern of selective muscle involvement corresponding to clinical severity. In mild cases, there was complete sparing of thigh muscles and selective involvement of tibialis anterior and soleus. In moderate cases, there was predominant involvement of rectus femoris, vastus lateralis and hamstring muscles and diffuse involvement of anterior compartment and soleus. Patients with nemaline myopathy secondary to mutations in the skeletal muscle alpha-actin (ACTA1) gene showed diffuse involvement of thigh and leg muscles with relative sparing of the gastrocnemii. Selective muscle involvement in both genetic categories was distinct from what has been reported in other congenital myopathies. We conclude that muscle MRI may be applied to distinguish nemaline myopathy from other conditions with similar clinical and histopathological features, to supplement clinical assessment in individual patients and to help direct genetic testing.

Actins↗

PubMed1991

Functionally complex muscles of the cat hindlimb. II. Mechanical and architectural heterogenity within the biceps femoris.

The goal of this study was to analyze the architecture of the cat biceps femoris (BF), a multifunctional hamstring muscle, and to evaluate the relationships between muscle architecture, limb position, and muscle function during natural movement. The BF muscle consists of three neuromuscular compartments: anterior (BFa), middle (BFm) and posterior (BFp). Each compartment is innervated by a separate nerve branch. Nerve branch stimulation and 2-dimensional surface EMG recordings showed that individual compartment territories were discrete and non-overlapping with well-defined borders. Comparisons of the three compartments revealed consistent differences in architecture, relationship to the skeleton, and function. The BFa crossed only the hip joint and appears to function as a pure hip extensor. The BFm had equal lever arm lengths to the hip and knee joints, appears to function as a hip extensor, and may contribute to knee flexion or femoral rotation. The BFp had a greater lever arm to the knee, functions as a knee flexor, and may contribute to hip extension, femoral rotation or ankle extension. Measurements of individual fascicles from the three compartments revealed a surprising range of lengths, 3.3-12.0 cm. Microdissection of gold-stained tissue showed that fascicles from all compartments were comprised of interdigitated, short fibers (range: 0.6-5.0 cm; average 2.14 cm) arranged in-series in fascicles, running parallel to the origin-insertion axis of each muscle compartment. In regions of fiber interdigitation, the fiber endings were round and tapered (taper lengths: 1-11 mm) although flat, tapering endings like ribbons were occasionally found. As hip and knee joint angles were varied over physiological ranges corresponding to minimal to maximal muscle length, fascicles of the three compartments changed length disproportionately. Long BFa fascicles maximally lengthened 10-18%, consistent with in vivo length measures during treadmill locomotion. However, the long BFp fascicles lengthened 25-45%, and the relatively short fascicles near the BFm/BFp border maximally lengthened 45-53%. How do these unexpectedly large length changes affect sarcomere lengths? Using laser diffraction to measure sarcomeres, static fascicle and sarcomere lengths were compared in muscles that went into rigor mortis after fixing the hip and knee joint angles. Sarcomeres within the short BFm/BFp and long BFp fascicles consistently lengthened proportionately less than the whole fascicle. It remains to be determined how and where the fascicle length changes are dissipated in the connective tissue between the interdigitated muscle fibers and whether such a series-compliance operates during the large excursions over which this muscle normally works.

Animals↗

PubMed1988

Electrically elicited co-contraction of thigh musculature after anterior cruciate ligament surgery. A description and single-case experiment.

The purpose of this article is to describe a method for strengthening the quadriceps femoris muscle in a patient after anterior cruciate ligament (ACL) surgery. The method incorporates electrically elicited co-contraction of the quadriceps femoris and hamstring muscles. A single-case experimental design based on a split-middle (ABAB) technique was used to assess the effects of the systematic administration and withdrawal of electrical stimulation with respect to changes in knee isometric extension and flexion torque and circumferential measurements of the thigh in a patient six weeks after ACL reconstruction. Results show increases in extension and flexion torque and thigh circumferential measurements that are associated with both stimulation (treatment) phases in addition to a maintenance effect demonstrated during the withdrawal phase. In this patient, the technique appears to be effective in increasing muscle strength and circumferential measurements, particularly quadriceps femoris muscle torque. Implications and suggestions for future research are included.

Adult↗

PubMed2005

The effectiveness of 3 stretching techniques on hamstring flexibility using consistent stretching parameters.

This study compares the effects of 3 common stretching techniques on the length of the hamstring muscle group during a 4-week training program. Subjects were 19 young adults between the ages of 21 and 35. The criterion for subject inclusion was tight hamstrings as defined by a knee extension angle greater than 20 degrees while supine with the hip flexed 90 degrees . The participants were randomly assigned to 1 of 4 groups. Group 1 (n = 5) was self-stretching, group 2 (n = 5) was static stretching, group 3 (n = 5) was proprioceptive neuromuscular facilitation incorporating the theory of reciprocal inhibition (PNF-R), and group 4 (n = 4) was control. Each group received the same stretching dose of a single 30-second stretch 3 days per week for 4 weeks. Knee extension angle was measured before the start of the stretching program, at 2 weeks, and at 4 weeks. Statistical analysis (p < or = 0.05) revealed a significant interaction of stretching technique and duration of stretch. Post hoc analysis showed that all 3 stretching techniques increase hamstring length from the baseline value during a 4-week training program; however, only group 2 (static stretching) was found to be significantly greater than the control at 4 weeks. These data indicate that static stretching 1 repetition for 30 seconds 3 days per week increased hamstring length in young healthy subjects. These data also suggest that active self-stretching and PNF-R stretching 1 repetition for 30 seconds 3 days per week is not sufficient to significantly increase hamstring length in this population.

Adult↗

PubMed1982

Flexibility training: ballistic, static or proprioceptive neuromuscular facilitation?

The effects of stretching techniques on the flexibility of the shoulder, trunk, and hamstring muscles were compared in college men. Subjects were randomly assigned to one of 4 groups: control (n=10), ballistic (n=11), static (n=10), or proprioceptive neuromuscular facilitation (PNF) (n=12). Baseline measurements (Leighton flexometer) were obtained on 2 separate days prior to and following a 3-day per week, 6-week flexibility training program. A 4x3 (subject group x muscle group) unweighted mean factorial analysis of variance for the difference scores (post minue pre) revealed significant (p less than 0.05) main effects for the 4 subjects groups and the 3 muscle groups. Post hoc analysis showed that only the PNF group had flexibility increases (10.6 degrees) greater than the control (3.4 degrees), and that the hamstrings (9.4 degrees increase) improved more than the trunk (5.2 degree increase). Furthermore, reliability was generally higher for the post-training scores, and the variability between days was lower for the post-training scores of the shoulder and hamstrings (p less than 0.05). The significant (p less than 0.05) between-day changes in flexibility pre-training confirm the importance of establishing baseline data prior to any training study. The findings indicate that PNF may be the preferred technique for improving flexibility, and that flexibility training results in an increased consistency of flexibility scores.

Adult↗

PubMed2001

Anterior tibial translation during different isokinetic quadriceps torque in anterior cruciate ligament deficient and nonimpaired individuals.

STUDY DESIGN: Factorial quasi-experimental design. OBJECTIVES: To quantify the effect of different levels of isokinetic concentric and eccentric knee extensor torques on the anterior tibial translation in subjects with anterior cruciate ligament (ACL) deficiency. Electromyogram (EMG) activity of 4 leg muscles was recorded in order to detect any co-activation of extensors and flexors. BACKGROUND: The rehabilitation after an ACL injury is of importance for the functional outcome of the patient. In order to construct a rehabilitation program after that injury, it is important to understand the in vivo relationships between muscle force and tibial translation. METHODS AND MEASURES: Twelve patients with unilateral ACL injury and 11 uninjured volunteers performed 36 repetitions of a quadriceps contraction at different isokinetic concentric and eccentric torque levels, on a KinCom machine (60 degrees x s(-1)), with simultaneous recordings of tibial translation (CA-4000) and EMG activity from quadriceps and hamstrings muscles. Tibial translations and EMG levels were normalized to the maximum of each subject. RESULTS: The individual anterior tibial translation increased with increased quadriceps torque in a similar manner in both quadriceps contraction modes in all legs tested. During concentric mode, translation was similar in all groups, but during eccentric mode, the mean translation was 38% larger in the ACL injured knees. No quadriceps-hamstrings co-activation occurred in any test or group. CONCLUSIONS: An ACL deficient knee can limit the translation within a normal space during concentric muscle activity but not during eccentric activity. That limitation depends on other mechanisms than hamstrings co-activation.

Adolescent↗

PubMed2006

A new self-diagnostic test for biceps femoris muscle strains.

OBJECTIVE: We compared a self-performed diagnostic test that we have been using since 1987, with other commonly used clinical tests for biceps femoris muscle-strain injuries. SETTING: Private practice focusing on sports injuries. PATIENTS: One-hundred forty professional male soccer players (ages 17 to 33 years) with a history and clinical findings of a pulled hamstring muscle (patients with direct trauma were excluded) had an ultrasound-proven grade I or II biceps femoris muscle injury. INTERVENTIONS: In these ultrasound-positive patients, the "taking off the shoe" test (TOST) was performed by the patient himself on both the affected and unaffected legs; and the physician then performed the resisted range of motion, passive range of motion, and active range of motion tests. RESULTS: The TOST had a sensitivity and specificity of 100%, and a positive predictive value and an negative predictive value of 100% for biceps femoris injury as found on ultrasound. The other muscle tests had an average sensitivity of 57%, specificity of 100%, accuracy of 79%, and negative predictive value of 70%. CONCLUSION: This preliminary, nonblinded observational study of the TOST found it to be more reliable than other commonly used clinical tests for hamstring tears. The clinical value of this easy-to-perform test should be evaluated in a prospective fashion.

Adolescent↗

PubMed1985

Painful muscle spasm reversed by magnesium sulphate. A case report.

A 25-year-old paraplegic man who had sustained a T3/T4 vertebral compression fracture 3 years previously presented with severe, painful spasm of the left hamstring muscle group of 2 hours' duration. This spasm produced extreme knee flexion of a degree which held the left foot posterior to the right buttock. An intravenous injection of 2 g magnesium sulphate produced immediate relief. Possible mechanisms of action of magnesium are discussed.

Adult↗

PubMed1994

Reflex hamstring contraction latency in anterior cruciate ligament deficiency.

Decreased dynamic stability of the knee joint associated with functional disability is a feature of anterior cruciate ligament deficiency (ACLD). The purposes of this study were to examine the between-limbs difference in reflex contraction latency of the hamstring muscles in patients with unilateral ACLD and to investigate its relationship with instability and function. Fifty patients with arthroscopically diagnosed unilateral ACLD were measured bilaterally for reflex hamstring contraction latency (RHCL), and 20 normal volunteers were similarly tested. The subjects were measured in a position of single-limb full weight-bearing with the knee flexed 30 degrees. An anteriorly directed shear force was applied to the tibia, and surface electromyographs (EMGs) recorded the activity of the hamstrings in response to the applied force. The latency of contraction was defined as the time from initial tibial movement, identified by accelerometry, to the onset of increased hamstring EMG activity. Both legs were tested and a between-limbs difference was computed. A significant difference in RHCL was found between the limb with ACLD and the control limb. The mean RHCL of the limb with ACLD was nearly double that of the unaffected limb, for a significant mean between-limbs difference (p < 0.05). The mean between-limbs difference for the control subjects was not statistically significant. The conclusion is that patients with ACLD have an increased RHCL of the injured leg. As the RHCL is dependent on proprioceptive activity around the joint, it can be used as a measure of proprioceptive ability. The loss of the neurophysiological protective reflex involving the anterior cruciate ligament and hamstrings in patients with ACLD is likely to be a contributory factor in the decreased joint stability experienced by these patients.

Adult↗

PubMed1990

[Referral pattern, diagnoses and occurrence of short muscles in children and adolescents in an orthopedic specialist practice].

The patterns of referral for 600 consecutive children and adolescents under the age of 17 years were analysed and the symptoms were compared with the diagnoses. 40% were referred because of foot problems, 20% had mobility problems and 20% had pain in the back or extremities. Out of the 240 patients with foot problems, these could be confirmed in 44%. 30% had merely short muscles and 7% had, in addition, spasticity. 70% out of the 110 patients referred on account of flat foot had too short achilles tendons. 50% out of the 600 patients referred had short achilles tendons and/or hamstring muscles. In 20%, the short muscles alone could explain the symptoms experienced by the patients. Short heel tendons are found with broad fore-feet, cavus and valgus feet, loose subtaloid joints, heel exostoses, pain in the heel and in the calf. Short hamstrings result in a shuffling gait, high-riding patellae with periodic pain, pain on the posterior aspect of the thigh and a straight transition in the thoraco-lumbar region with subsequent Scheuermann's disease. The length of the muscles should, therefore, be investigated. If they are too short, they should be stretched for one minute every twelfth hour to obtain optimal elasticity and length.

Achilles Tendon↗