PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Hamstring Muscles”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,621 records · Page 90Linked to original sources

Sagittal knee kinematics after hamstring lengthening.

The purpose of this study was to analyze sagittal knee kinematics after hamstring lengthening. A retrospective analysis was performed of 16 children (32 knees) with cerebral palsy who underwent hamstring lengthening as an isolated surgical procedure. Gait analysis was performed before surgery and at a minimum of 1 year after surgery. Decreased stance maximum knee flexion, stance minimum knee flexion, swing maximum knee flexion, and swing minimum knee flexion were noted. Total knee excursion increased. The present study confirmed the previously reported increased total knee excursion with decreased stance minimum and swing maximum knee flexion.

Adolescent↗

Hamstring and quadriceps strength balance in normal and hamstring anterior cruciate ligament-reconstructed subjects.

OBJECTIVE: The purpose of this study was to evaluate and characterize the agonist-antagonist strength balance (hamstring/quadriceps [H/Q] ratio and dynamic control ratio [DCR]) about the knee specific to velocity, range of motion, and contraction type. We hypothesized that there would be systematic variation in the H/Q ratio and DCR based on knee joint angle, angular velocity, and contraction type. We also hypothesized that these ratios would be altered in the anterior cruciate ligament (ACL)-reconstructed group in favor of protecting the ACL graft (relative knee flexor strength when strain on the ACL is the greatest). DESIGN: Cross-sectional design. SETTING: A tertiary care sport medicine clinic. PATIENTS OR PARTICIPANTS: Sixteen subjects more than 1 year after hamstring tendon ACL reconstruction were compared with 30 active uninjured control subjects. INTERVENTIONS: Isokinetic strength testing was performed over 5 degrees to 95 degrees knee joint range of motion, 5 angular velocities (50, 100, 150, 200, 250 degrees/s), for concentric and eccentric contractions. MAIN OUTCOME MEASUREMENTS: Angle and velocity-matched H/Q ratio maps and DCR maps were produced for each group. Difference maps allowed quantification of the differences between the groups. RESULTS: Angle and velocity-matched H/Q ratio maps demonstrated systematic variation based on joint angle, velocity, and contraction type for both the control (H/Q, approximately 0-1.42; DCR, approximately 0-1.57) and the ACL-reconstructed group (H/Q, approximately 0-1.33; DCR, approximately 0-1.35). Difference maps demonstrate regional (angle and velocity-specific) alteration in the ratio between the ACL-reconstructed and control groups. CONCLUSIONS: Specific imbalances were demonstrated in the ACL-reconstructed group compared with control. In high knee flexion angles, the low H/Q ratio may represent a compromised ability of the hamstrings to stabilize the knee joint throughout the full range of motion. Near full knee extension shifts in favor of the knee flexors may represent an attempt to stabilize the knee at the angle of greatest ACL strain. These finding have implications for graft donor site selection and postoperative rehabilitation as well as provide insight into the neuromuscular control of the knee.

Adult↗

Two-year trends in physical performance following supervised exercise among community-dwelling older veterans.

The extent to which exercise can delay the normal decline in physical performance associated with aging is unknown. We examined the impact of 2 years of supervised exercise on cardiovascular fitness, flexibility, and strength in a group of elderly (age 65-74) veterans. Seventy-five patients exercised 3 days/week for 90-minute sessions emphasizing aerobic, flexibility, and strength development. Thirty-six (47%) completed 2 years of a voluntary supervised exercise program (n = 25 with complete data). Over a 2-year follow-up period, cardiovascular outcome variables improved significantly: metabolic equivalents increased 20% (7.4 +/- 2.2 to 9.0 +/- 2.4, P less than 0.001) and submaximal heart rate decreased 7% (68.5 +/- 8.0 to 63.6 +/- 8.4 beats/minute, P = 0.02). Resting heart rate decreased 8% (131.4 +/- 14.8 to 121.0 +/- 18.5 beats/minute, P = 0.06), but this difference did not reach statistical significance. Flexibility, measured by hamstring length, improved 11% (57.5 +/- 15.1 to 64.0 +/- 11.1 degrees, P = 0.02). Strength variables did not improve. The study indicates that improvements in cardiovascular function and flexibility achieved by the elderly in the early stages of an exercise program can be maintained for at least 2 years.

Aged↗

Evaluation of warm-up for improvement in flexibility.

The purpose of this investigation was to evaluate the effects of warming the joints by jogging and then stretching on increases in joint flexibility. Subjects were 51 students enrolled in a physical conditioning class assigned to a jog and then stretch (JS), stretch and no jog (S), or a control group (C). Both the JS and S groups performed a series of stretching exercises 2 days a week for 9 weeks, with the JS group jogging for 5 minutes prior to stretching. Subjects were pretested and posttested for shoulder, hamstrings, trunk, and ankle flexibility with a Leighton flexometer. Results of t-tests indicated that significant increases in flexibility occurred for all of the joint angles evaluated for both the JS and S groups with the exception of trunk flexibility for the JS group. An analysis of variance (ANOVA) of gain scores indicated a significant gain in ankle flexibility for the JS group compared to S and C groups. The S group produced a significant gain in trunk flexibility compared to the JS group. Both JS and S groups were effective in improving flexibility, but when the gain scores were compared the results were variable. The data from this study again demonstrate that increases in flexibility can occur as a result of a static stretching training program. However, the results do not support the claim that warming the muscles prior to stretching by jogging will result in significant increases for all of the joint angles evaluated. Both methods offer possible advantages associated with improving joint flexibility.

Adult↗

Open-loop position control of the knee joint using electrical stimulation of the quadriceps and hamstrings.

The clinical acceptability of functional electrical stimulation (FES) as an aid for restoration of paraplegic gait is limited by the inability to accurately and repeatedly position the lower extremity. To gain insight into the causes of and possible solutions to this problem, the responses of the quadriceps and hamstrings to FES were studied in able-bodied subjects. Isometric torque was dependent on knee angle and changed unpredictably with time. An open-loop feedforward knee-joint position controller was also tested. The results demonstrated that it is beneficial to account for the dependence of torque on position, that modifications to this open-loop controller might improve accuracy and that closed-loop control may be essential for functional restoration of gait.

Adolescent↗

Safety of high-dose botulinum toxin type A therapy for the treatment of pediatric spasticity.

This retrospective chart review examines the safety of high-dose (> or = 15 U/kg body weight or > or = 800 total units) botulinum toxin type A (BOTOX, Allergan Inc., Irvine, CA) in children and young adults with spasticity. Ninety-four children weighing < 45 kg received a mean total dose of 334.1 U or 19.1 U/kg. Fourteen young adults weighing > or = 45 kg received a mean total dose of 927.3 U or 15.2 U/kg. Adverse events were reported by 3 of the 108 patients (2.8%) and included single instances of rash and enuresis. The only serious adverse event consisted of mild, generalized botulism in a 13-year-old patient who received a 23 U/kg dose to the hamstrings and gastrocnemius/soleus bilaterally. No serious adverse events were noted in children weighing < 45 kg who received botulinum toxin type A doses of 15 to 22 U/kg of body weight or in young adults > or = 45 kg who received total doses of 800 to 1200 U in a single injection protocol. High-dose botulinum toxin type A is safe for the treatment of spasticity in children and young adults.

Adolescent↗

Remodelling of the sacrum in high-grade spondylolisthesis: a report of two cases.

Two young patients are described, who were operated on for high-grade spondylolisthesis. A good posterolateral fusion was achieved, without decompression and without reduction. The clinical course was favourable, the tight hamstring syndrome resolved. Disappearance of the posterior-superior part of the sacrum and of the posterior part of the L5-S1 disc was observed on comparing pre- and postoperative magnetic resonance (MR) images. This resulted in normalisation of the width of the spinal canal. Around the L5 nerve roots in the L5-S1 foramina some fat reappeared. These anatomical changes on MRI could play a role in the disappearance of clinical symptoms.

Adolescent↗

Cruciate ligament forces in the human knee during rehabilitation exercises.

OBJECTIVE: To determine the cruciate ligament forces occurring during typical rehabilitation exercises.Design. A combination of non-invasive measurements with mathematical modelling of the lower limb.Background. Direct measurement of ligament forces has not yet been successful in vivo in humans. A promising alternative is to calculate the forces mathematically. METHODS: Sixteen subjects performed isometric and isokinetic or squat exercises while the external forces and limb kinematics were measured. Internal forces were calculated using a geometrical model of the lower limb and the "dynamically determinate one-sided constraint" analysis procedure. RESULTS: During isokinetic/isometric extension, peak anterior cruciate ligament forces, occurring at knee angles of 35-40 degrees, may reach 0.55x body-weight. Peak posterior cruciate ligament forces are lower and occur around 90 degrees. During isokinetic/isometric flexion, peak posterior cruciate forces, which occur around 90 degrees, may exceed 4x body-weight; the anterior cruciate is not loaded. During squats, the anterior cruciate is lightly loaded at knee angles up to 50 degrees, after which the posterior cruciate is loaded. Peak posterior cruciate forces occur near the lowest point of the squat and may reach 3.5x body-weight. CONCLUSIONS: For anterior cruciate injuries, squats should be safer than isokinetic or isometric extension for quadriceps strengthening, though isokinetic or isometric flexion may safely be used for hamstrings strengthening. For posterior cruciate injuries, isokinetic extension at knee angles less than 70 degrees should be safe but isokinetic flexion and deep squats should be avoided until healing is well-advanced. RELEVANCE: Good rehabilitation is vital for a successful outcome to cruciate ligament injuries. Knowledge of ligament forces can aid the physician in the design of improved rehabilitation protocols.

Adult↗

Recurrent posterior thigh symptoms detrimental to performance in rugby union: predisposing factors.

Recurrent hamstring injury is a very common problem in rugby union, but has been largely ignored in the literature. It is concluded that a multifactorial aetiology may be present, and that these symptoms may be part of a continuum of symptoms that may lead to more serious injuries. Effective management needs to focus not just locally, but include proximal issues such as lumbo-pelvic stability and correcting lumbar spine dysfunction. The factors addressed in a prevention programme are likely to contribute to performance gains.

Biomechanical Phenomena↗

Effects of short-term isokinetic training on standing long-jump performance in untrained men.

The purpose of this study was to examine the effects of a 6-week isokinetic training program on quadriceps and hamstrings peak torque (PT) and standing long-jump (SLJ) performance. Twelve untrained men (age 31.4 +/- 4.2 years, mean +/- SD) were tested at a velocity of 1.75 rad.s(-1) (100 degrees.s(-1)), before and after a 6-week control period and on completion of a 6-week training program. Training consisted of 3 sets of 10 repetitions, 3 days per week, for 6 weeks. Repeated-measures analysis-of-variance analyses revealed that quadriceps PT increased, on average, by 10.5% as a result of training (p < 0.01). No significant changes in hamstrings PT (p = 0.062) and SLJ performance occurred as a result of training (p > 0.05). The major finding of this study was that PT gains subsequent to isokinetic resistance training did not influence functional performance. That open-chain training did not affect the performance of a closed-chain activity is unsurprising, but on these grounds of nonfunctionality, the use of moderate velocity isokinetic dynamometry in rehabilitation and performance assessment for closed-chain sports needs addressing in future research.

Adaptation, Physiological↗

Kinematic analysis of lumbar and hip motion while rising from a forward, flexed position in patients with and without a history of low back pain.

STUDY DESIGN: This study analyzed two groups of individuals during return to an upright position (extension) from a forward, bent position. Group 1 (n = 12) included individuals with no history of low back pain who were currently asymptomatic, and group 2 (n = 12) included individuals with no history of low back pain. OBJECTIVES: To determine the amount and pattern of lumbar spine and hip motion that occur as an individual rises from a forward, flexed position, to determine if differences exist in this measurement between individuals with and without a history of low back pain, and to determine if hamstring length is related to the pattern of motion. SUMMARY OF BACKGROUND DATA: Reports of interaction between lumbar spine and hip movement vary for forward bending and extension. Differences may be a result of variations in measurement methods, loading conditions, or the pathology present, such as low back pain. METHODS: A three-dimensional optoelectric motion analysis system was used to measure the amount and velocity of lumbar spine and hip motion during extension. Each participant in the study performed three trials of a complete flexion-extension cycle at a self-selected speed. The data for the extension portion of the cycle were averaged and used for statistical analysis. Hamstring length also was determined using two clinical tests, the passive straight-leg raise and the active knee-extension tests. RESULTS: The pattern of movement was described by calculating lumbar to hip extension ratios for each 25% interval of total extension. Individuals with a history of low back pain tended to move from the lumbar spine earlier than those with no history of low back pain, especially in the initial 25% of the extension motion. For all participants, mean lumbar to hip extension ratios were 0.26 for 0-25% of extension, 0.61 for 25-50%, 0.81 for 50-75%, and 2.3 for 75-100%. The lumbar to hip ratios were different in each 25% interval, demonstrating that the hips had a greater contribution to early extension, with the lumbar spine contribution increasing in the middle intervals and becoming the primary source of motion in the final interval. When lumbar to hip extension ratios were compared with corresponding intervals of flexion, three of four were positively correlated to flexion ratios, demonstrating a reversible lumbopelvic rhythm. Although participants with a history of low back pain had significantly tighter hamstrings than participants with no history of low back pain, hamstring length was not correlated with any of the kinematic characteristics during extension. CONCLUSIONS: Participants who were currently asymptomatic but had a history of low back pain moved in a manner similar to that of participants with no history of low back pain except that they demonstrated greater lumbar motion and velocity during the initial phase of extension. This may have been the result of low back pain or a contributing factor in recurrent low back pain.

Adult↗

Tendon-to-bone healing of a quadrupled hamstring tendon graft fixed with biodegradable screws in an immature athlete: a radiologic, arthroscopic, histologic, and electromicroscopic investigation.

Abstract Quadrupled hamstring tendon is one of the most commonly used ligamentous substitutes in anterior cruciate ligament reconstruction. We describe a case of a young athlete who sustained a rerupture of a semitendinosus-gracilis autograft fixed with biodegradable screws 2 years after primary surgery. Radiologic, arthroscopic, histologic, and electromicroscopic investigation showed tendon-to-bone healing of the soft tissue graft and partial degradation of the interference screws.

Adolescent↗

Quadriceps weakness and osteoarthritis of the knee.

BACKGROUND: The quadriceps weakness commonly associated with osteoarthritis of the knee is widely believed to result from disuse atrophy secondary to pain in the involved joint. However, quadriceps weakness may be an etiologic factor in the development of osteoarthritis. OBJECTIVE: To explore the relation between lower-extremity weakness and osteoarthritis of the knee. DESIGN: Cross-sectional prevalence study. SETTING: Population-based, with recruitment by random-digit dialing. PARTICIPANTS: 462 volunteers 65 years of age or older. MEASUREMENTS: Radiographs of the knee were graded for the presence of osteoarthritis. Knee pain and function were assessed with the Western Ontario and McMaster Universities Arthritis Index, the strength of leg flexors and extensors was assessed with isokinetic dynamometry, and lower-extremity lean tissue mass was assessed with dual-energy x-ray absorptiometry. RESULTS: Among participants with osteoarthritis, quadriceps weakness, but not hamstring weakness, was common. The ratio of extensor strength to body weight was approximately 20% lower in those with than in those without radiographic osteoarthritis. Notably, among women with tibiofemoral osteoarthritis, extensor weakness was present in the absence of knee pain and was seen in participants with normal lower-extremity lean mass (extensor strength, 30.1 lb-ft for those with osteoarthritis and 34.8 lb-ft for those without osteoarthritis; P < 0.001). After adjustment for body weight, age, and sex, lesser quadriceps strength remained predictive of both radiographic and symptomatic osteoarthritis of the knee (odds ratio for prevalence of osteoarthritis per 10 lb-ft loss of strength, 0.8 [95% CI, 0.71 to 0.90] for radiographic osteoarthritis and 0.71 [CI, 0.51 to 0.87] for symptomatic osteoarthritis). CONCLUSION: Quadriceps weakness may be present in patients who have osteoarthritis but do not have knee pain or muscle atrophy; this suggests that the weakness may be due to muscle dysfunction. The data are consistent with the possibility that quadriceps weakness is a primary risk factor for knee pain, disability, and progression of joint damage in persons with osteoarthritis of the knee.

Aged↗

The effects of antagonist prefatigue on agonist torque and electromyography.

This study assessed the effects of hamstring prefatigue on peak torque, peak power, time to peak torque, knee angle of peak torque, and electromyography (EMG) activity of the hamstrings and quadriceps group during knee extensions at angular velocities of 60 degrees, 180 degrees, and 300 degrees.s(-1). Twenty Division I wrestlers performed 5 maximal knee extensions in prefatigued and nonfatigued conditions of the hamstring group. This study demonstrated that when the hamstrings were prefatigued, the quadriceps produced significant decreases in peak torque of 1.7% (p < 0.05), peak power of 11% (p < 0.05), and rate to peak torque of 6.4% (p < 0.01) as compared with the nonfatigued state. When the hamstrings were prefatigued, they produced a 25% greater amount of EMG activity during knee extension (p < 0.01) than when not prefatigued. There was no significant difference in quadriceps EMG activity whether the hamstring group was prefatigued or not (p > 0.05). The decrease in quadriceps peak torque during the prefatigued condition was more pronounced (p < 0.01) at an angular velocity of 60 degrees.s(-1) than at 180 degrees or 300 degrees.s(-1). In other words, prefatiguing the antagonist appears to be most detrimental to torque output of the quadriceps in the condition that most closely replicates the speed at which "isotonic" weight training occurs (60 degrees.s(-1)) and suggests a limitation to agonist-antagonist superset training.

Adult↗

The effect of uniform heating on the biomechanical properties of the intervertebral disc in a porcine model.

BACKGROUND CONTEXT: The use of minimally invasive lumbar intradiscal heating techniques, including intradiscal electro-thermal therapy (IDET), endoscopic radio-frequency annuloplasty, nucleoplasty and laser discectomy, for chronic lumbar discogenic pain and contained disc herniation has recently gained popularity. The purported therapeutic mechanisms of these interventions include subtotal nuclectomy, annular nociceptor ablation, and stabilization of the annular fibers. Basic science data elucidating the biomechanical and histomorphologic alterations of heat treatments on disc remain sparse. PURPOSE: The purpose of this study is to examine the effects of uniform heating on biomechanical properties and histomorphology of intervertebral disc tissues using a porcine model. STUDY DESIGN/SETTING: In a laboratory setting, porcine functional spinal units consisting of vertebra-nucleus pulposus-vertebra core and porcine hamstring tendons were harvested. Studies were performed on these tissue samples by uniformly heating the specimens in a constant temperature water bath. Ten porcine lumbar disc core and twenty-five porcine hamstring tendons were utilized as the subjects for this study. The effects of uniform heat treatments on disc core and hamstring tendon were measured for shrinkage, stiffness, and load to failure strength. Histomorphological study was also carried on the same specimen. METHODS: The porcine vertebra-nucleus pulposus-vertebra segments were cored to a uniform 1-cm diameter. The hamstring tendons were cut to uniform 1.2-inch lengths. The tendon specimens were divided into groups of five each and heated in constant temperature water baths of 60 degrees C, 65 degrees C, 70 degrees C, or 75 degrees C for 10 min. Unheated specimens served as controls. The disc core specimens were divided in two group of five each, and tested at room temperature or after immersion in a 70 degrees C bath. The shrinkage was monitored during immersion in the water bath. Biomechanical testing to failure was carried out using mechanical loading on an MTS servohydraulic testing machine operating under stroke control. Strength and stiffness of the tissue was determined. Histomorphology was studied by staining the specimen with hematoxylin and eosin (H&E), and examined under 200 times magnification. Non-heated controls were used for comparisons. RESULTS: The porcine hamstring tendons had no measurable shrinkage in specimens heated up to 65 degrees C. At temperatures above 65 degrees C, the shrinkage was concluded within 2 min of immersion and 70 degrees C appeared to be the optimal temperature, as temperatures higher than this did not demonstrate incremental effects. The disc core samples were heated to 70 degrees C (optimum temperature), and there appeared to be gross contraction of the disc core circumference to visual inspection, but no measurable lengthwise shrinkage could be appreciated. Histologically, the specimens demonstrated progressive loss of individual collagen fiber outline as the temperature increased. In the tendons, at 75 degrees C all of the fibers appear to be fused together, and the voids between individual collagen fibers were no longer present. Biomechanical testing revealed that the tendons undergo a substantial reduction in stiffness after heating. The mean tendon stiffness for the unheated specimens was 19,356 psi, while the corresponding value for the heated tendons was 1023 psi. These were significantly different using the paired t-test at p=0.0043. For the disc core samples, there was no significant difference in either stiffness (p=0.182) or failure strength (p=0.998) after heating. All failures occurred in mid-substance of the specimen. CONCLUSIONS: The application of uniform heating to nucleus pulposus disc core caused visible contraction of its circumference but not lengthwise shrinkage. The same heating shrinks the hamstring tendon and reduces its stiffness. Ultimate failure strength of the disc core specimen remains unchanged. The failure data was not obtainable for the tendon due to premature slippage from the fixation apparatus before failure. The results of this study fail to support a biomechanical justification for the application of uniform heat treatment to the whole intervertebral disc. Heating annulus fibrosus and nucleus pulposus separately to specific temperatures may have potential clinical benefits.

Animals↗

Spinal myoclonus complicating spasticity in spinal cord injury: a case study.

A case of spinal myoclonus that complicated spasticity management is presented. A 37-year-old man with a C6 American Spinal Injury Association class B spinal cord injury was referred for treatment of spasticity. He had failed previous treatments with baclofen and dantrolene but was partly relieved by diazepam, although with unacceptable side effects. Further evaluation, including simultaneous electroencephalogram, videotaping, and electromyography of the quadriceps, anterior tibialis, posterior tibialis, and medial hamstring suggested myoclonic jerks of spinal origin that initiated episodes of unsustained clonus. During the worst episodes, myoclonic jerks came once every 16 to 22 seconds and persisted for 4 to 5 hours. Each episode of clonus lasted approximately 4 to 6 seconds. Treatment with valproic acid greatly diminished the frequency of myoclonic jerks with minimal side effects. Functionally, the patient was much less fatigued and better able to maintain his full time employment.

Activities of Daily Living↗

Isokinetic strength of the quadriceps and hamstrings and functional ability of anterior cruciate deficient knees in recreational athletes.

OBJECTIVE: To test the hypothesis that increasing the hamstrings and quadriceps (H:Q) isokinetic strength ratio will, in the short term, improve the functional ability of an anterior cruciate ligament (ACL) deficient knee. METHODS: The isokinetic muscular characteristics at a speed of 60 degrees s-1 and 180 degrees s-1 of 46 recreational athletes with an arthroscopically confirmed ACL tear were determined using the Cybex II+ isokinetic dynamometer. The variables tested included peak torque, endurance ratio, total work output, and explosive power. Functional ability was scored with the Cincinnati rating system, measuring the severity of pain and swelling, the degree of giving way, and the overall ability to walk, run, ascent and descent stairs, jump and twist. RESULTS: Among all muscular characteristics, the H:Q ratio at 180 degrees s-1 at 30 degrees of knee flexion was shown to have the highest correlation to the functional score (r = 0.6249, P < 0.001). All variables involving hamstring strength were shown to be significantly correlated to the functional ability score (P < 0.01), while none of the variables involving quadriceps strength showed significant correlation with the functional ability of the injured knee. CONCLUSIONS: The H:Q ratio is strongly correlated to the functional ability of ACL deficient knees in Chinese recreational athletes. It could be used as an additional measure to guide in the decision making process in the management of ACL deficient knees.

Adult↗

Knee strength after total knee arthroplasty.

Fifty-two knees in normal healthy subjects and 32 knees more than 2 years after total knee arthroplasty (TKA) were evaluated. Average isometric extension peak torque values in TKA patients were reduced by up to 30.7% (P=.01). Isometric flexion peak torque values in patients with TKA were, on average, 32.2% lower than those from control subjects throughout the motion arc (P=.004). Knee Society Functional Scores were positively correlated to the average isometric extension peak torque (r=0.57; P=.004) and negatively correlated to the average isometric hamstring to quadriceps (H/Q) ratio (r=-0.78, P<.0001). Relatively greater quadriceps strength was associated with a better functional score. Older TKA patients (>/=70 years) generated lower isometric extension peak torque values in terminal extension than younger TKA patients (>24.2%; P=.05). Higher body mass index (BMI) was associated with relative quadriceps weakness (r=0.44; P=.007). These results suggest that more thorough rehabilitation after TKA would improve functional outcomes.

Aged↗