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PubMed1998

Adverse neural tension: a factor in repetitive hamstring strain?

The etiology and nature of repetitive hamstring strain is complex and not fully understood. The purpose of this study was to investigate the presence of adverse neural tension in 14 male Rugby Union players with a history of grade 1 repetitive hamstring strain. Comparison was made to an injury-free matched control group. Adverse neural tension was assessed using the slump test. Hamstring flexibility was measured using the active knee extension in lying test. Results indicated that 57% of the test group had positive slump tests, suggesting the presence of adverse neural tension. None of the control group had a positive slump test. Analysis of variance revealed no differences in flexibility between groups or between those demonstrating a positive or negative slump test. Results suggest that adverse neural tension may result from or be a contributing factor in the etiology of repetitive hamstring strain. Residual decreased flexibility is not apparent in this subject group.

Adolescent↗

PubMed2000

Relationship between quadriceps strength and rate of loading during gait in women.

One function of skeletal muscle is to serve as the body's shock absorbers and thus dampen rates of loading during activity. The aim of this cross-sectional study was to determine the significance of muscle strength on rates of loading during gait. Thirty-seven women (mean age: 34.5 +/- 8.2 years) were solicited by advertisement and placed into one of two groups-strength-trained or sedentary-on the basis of training history. They walked (10 trials) over a 10-m walkway at a controlled speed of 1.22-1.35 m/s while the rate of loading was sampled with a 1,000-Hz force platform. Quadriceps and hamstring strength was measured at 90 degrees/s with an isokinetic dynamometer. Statistical analyses (p < 0.05) included descriptive statistics and unpaired t tests for comparison between groups. The women in the sedentary group weighed more and had significantly less concentric and eccentric strength of the quadriceps and hamstrings relative to body weight than did those in the strength-trained group. In addition, they demonstrated significantly higher rates of loading (2.21 +/- 0.15 compared with 1.75 +/- 0.08%wt/ms) than those in the strength-trained group.

Adult↗

PubMed2000

Age-related variations of serum CK and CK MB response in females.

The objective was to determine whether serum creatine kinase (CK) and serum CK MB activity following exercise-induced muscle damage activity differs among females of varying menarchial status and to determine whether there is a relationship between serum estradiol (E2) concentration, CK, and CK MB activity. Fifteen menarchial (M), 15 premenarchial (P), and 10 postmenopausal (PM) females participated in the study. Exercise consisted of eccentric hamstring contractions. Estradiol concentrations were significantly higher in M women (p =.0001; M, 125.0 +/- 20.8 pg/mL, P, 54.6 +/- 38.6 pg/mL, PM, 46.2 +/- 34.6 pg/mL). Menarchial women had lower resting CK and CK MB activity and responded with a higher efflux of CK and CK MB post exercise (p =.0001). An inverse relationship was found between E2 concentration and baseline CK (p =.02) and CK MB activity (p =. 006). No relationship existed between post exercise efflux of CK and CK MB and E2 concentration. At rest, E2 influenced CK and CK MB activity across menarchial levels. However, E2 did not significantly reduce the level of CK and CK MB activity following this intense bout of eccentric exercise.

Adult↗

PubMed2003

The complementary role of the plantarflexors, hamstrings and gluteus maximus in the control of stance limb stability during gait.

This paper focuses on the contributions of the gluteus maximus, biceps femoris, gastrocnemius and soleus in maintaining the stability of the stance limb in the sagittal plane during the mid-stance phase of gait. In the absence of any one of these muscles, the potential compensatory changes in muscle activation are explored, the aim being to restore stability to the stance limb. The investigation was carried out by integrating musculoskeletal modelling, forward simulation and optimization techniques. We concluded that maintenance of stance limb stability requires a subtle interplay of muscle activations. Weakness in a single muscle is unlikely to be adequately compensated for by increasing or decreasing the activation of one muscle alone.

Extremities↗

PubMed1989

The RGO Generation II: muscle stimulation powered orthosis as a practical walking system for thoracic paraplegics.

The RGO Generation II reciprocating gait orthosis was jointly developed by Louisiana State University Medical Center and Durr-Fillauer Medical, Inc, to overcome four problems encountered with the existing model: 1) The high energy cost of locomotion; 2) the great arm strength required for patients to stand up from the seated position without assistance; 3) difficulty (especially for patients with hamstring contracture) in remaining standing owing to failure of the knee latch to lock except in full extension; and 4) problems in balancing when ambulating on an incline. The RGO Generation II employs concurrent electrostimulation of the rectus femoris and hamstrings to assist in rising and balancing and a ratchet-type latching device to improve safety and stability in standing. Alternating stimulation of the rectus femoris and contralateral hamstrings are used for locomotion. Testing in six patients with thoracic paraplegia demonstrated an average 30+% reduction in energy expenditure at a walking speed of .05 m/s and a 15+% reduction at .37 m/s; improved mobility and better balance on inclines; and unassisted rising in all patients. Walking range was increased from an average of 100 m to an average of 800 m. More research is needed to provide stair-climbing ability and to further reduce energy expenditure.

Adult↗

PubMed2004

Anterior cruciate ligament reconstruction with double-looped semitendinosus and gracilis tendon graft directly fixed to cortical bone: 5-year results.

Forty-three patients who had undergone an anterior cruciate ligament (ACL) reconstruction using a doubled semitendinosus and gracilis graft were prospectively reviewed at 5-year follow-up. All had suffered subacute or chronic tears of the ligament. At surgery, the femoral tunnel was drilled first through the antero-medial portal. The correct position of the femoral and tibial guide wire was checked fluoroscopically. A cortical fixation to the bone was achieved in the femur with a Mitek anchor, directly passing the two tendons in the slot of the anchor, and in the tibia with an RCI screw, supplemented with a spiked washer and bicortical screw. Rehabilitation was aggressive, controlled and without braces. The International Knee Documentation Committee (IKDC) form, KT-1000 arthrometer, and Cybex dynamometer were employed for clinical evaluation. A radiographic study was also performed. At the 5-year follow-up all the patients had recovered full range of motion and 2% of them complained of pain during light sports activities. Four patients (9.5%) reported giving-way symptoms. The KT-1000 side-to-side difference was on average 2.1 mm at 30 lb, and 68% of the knees were within 2 mm. The final IKDC score showed 90% satisfactory results. There was no difference between the 2-year and 5-year evaluations in terms of stability. Extensor and flexor muscle strength recovery was almost complete (maximum deficit 5%). Radiographic study showed a tunnel widening in 32% of the femurs and 40% of the tibias. A correlation was found between the incidence of tibial tunnel widening and the distance of the RCI screw from the joint (the closer the screw to the joint, the lower the incidence of widening). In conclusion, we can state that, using a four-strand hamstring graft and a cortical fixation at both ends, we were able to achieve satisfactory 5-year results in 90% of the patients.

Adolescent↗

PubMedDate not supplied

Functional analysis of untreated and reconstructed posterior cruciate ligament injuries.

Twenty patients with old ruptures of the PCL were analyzed. Ten patients were untreated, and ten patients had reconstruction of the PCL with the medial head of the gastrocnemius. The patients' gait was analyzed using high speed photography, footswitches, electromyography, and force plate. Patients were studied while walking, running, and stair-climbing. A Cybex muscle strength evaluation was also performed. Clinically, all patients had moderate to severe posterior instability. Five of the 20 patients also had posterolateral instability. Cybex testing showed quadriceps deficits in both reconstructed and untreated groups when comparing involved and uninvolved limbs. The reconstructed group also had deficits on hamstring Cybex testing. Footswitch data showed only minimal abnormalities. Gait velocity of walking was 91% of normal with a normal cadence. There was no significant difference in the single limb support times between the involved and uninvolved limbs in walking, fast walking, or running. The photometric data showed a tendency for increased knee flexion during the midstance phase of the gait cycle in comparing involved and uninvolved limbs. The knee flexion angles during midstance were similar in the patients with posterior instability when compared to the patients with the additional posterolateral instability. Force plate data showed decreased foot-floor reaction in the untreated group during terminal stance while walking. Similar findings were found in the reconstructed group during running.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed2000

Effects of sectioning the posterolateral structures on knee kinematics and in situ forces in the posterior cruciate ligament.

The objective of this study was to determine the effects of sectioning the posterolateral structures (PLS) on knee kinematics and in situ forces in the posterior cruciate ligament (PCL) in response to external and simulated muscle loads. Ten human cadaveric knees were tested using a robotic/universal force-moment sensor testing system. The knees were subjected to three loading conditions: (a) 134-N posterior tibial load, (b) 5-Nm external tibial torque, and (c) isolated hamstring load (40 N biceps/40 N semimembranosus). The knee kinematics and in situ forces in the PCL for the intact and PLS-deficient knee conditions were determined at full extension, 30 degrees, 60 degrees, 90 degrees, and 120 degrees of knee flexion. Under posterior tibial loading posterior tibial translation with PLS deficiency increased significantly at all flexion angles by 5.5+/-1.5 mm to 0.8+/-1.2 mm at full extension and 90 degrees, respectively. The corresponding in situ forces in the PCL increased by 17-19 N at full extension and 30 degrees of knee flexion. Under the external tibial torque, external tibial rotation increased significantly with PLS deficiency by 15.1+/-1.6 degrees at 30 degrees of flexion to 7.7+/-3.5 degrees at 90 degrees, with the in situ forces in the PCL increasing by 15-90 N. The largest increase occurred at 60 degrees to 120 degrees of knee flexion, representing forces two to six times of those in the intact knee. Under the simulated hamstring load, posterior tibial translation and external tibial and varus rotations also increased significantly at all knee flexion angles with PLS deficiency, but this was not so for the in situ forces in the PCL. Our data suggest that injuries to the PLS put the PCL and other soft tissue structures at increased risk of injury due to increased knee motion and the elevated in situ forces in the PCL.

Aged↗

PubMed1992

Value of isokinetic angle-specific torque measurements in normal and injured knees.

This study assessed the relationship between the isokinetic peak torque (PT) (speed of movement 60 and 180 degrees.s-1) and the angle-specific torques (ASTs) at 15 and 75 degrees of knee flexion in multiple contractions of the quadriceps and hamstrings in 80 subjects with a grade I knee injury. At every test speed, the Pearson product moment (r) and the Spearman rank (rs) correlation coefficients between the PT and ASTs were highly significant (P less than 0.001) for both muscle groups in the uninjured (r = 0.73-0.88, rs = 0.75-0.89) as well as in the injured (r = 0.63-0.91, rs = 0.65-0.91) knees. In both extremities, a great majority of the correlation coefficients exceeded 0.80, which was the predetermined threshold for the coefficients to exceed before the relationship could be considered clinically important. Using regression analysis, both extremities showed completely nonsystematic distribution of the residuals. The variability of the AST measurements was clearly higher than corresponding PT measurements. In conclusion, concerning healthy or grade I injured knees, the predictability of ASTs from PT was good; and, therefore, AST analyses offer little additional information about thigh muscle function than that obtained through the simpler and more commonly used measurement, PT analysis. Because of large variability, the routine use of the AST measurements for grade I knee injuries is not recommended.

Adult↗

PubMed1996

Cocontraction and phasic activity during GAIT in children with cerebral palsy.

Simultaneous activity of agonist and antagonistic muscles during a task is known as cocontraction. The primary aim of the present study was to use a cocontraction index (CI) to quantify differences in EMG activity between a group of CP and control children at two different walking speeds. The secondary aim was to compare the amount of time the muscles were activated ("on" thresholds) between the groups. Seventeen subjects volunteered for the study. One group consisted of 9 (7M, 2F) children with CP (age 12.7 +/- 2.8 years, mean +/- SD). The second group consisted of 8 able-bodied controls (7M, 1F). The discontinuous submaximal treadmill walking protocol had two 4min stages at 0% gradient. Speeds selected were 3 km.h-1 and 90% of the pre-determined fastest walking speed (FWS). Two sites of CI were measured from the EMGs of tibialis anterior and soleus (leg) and vastus lateralis and hamstrings (thigh). Significantly (p < 0.05) higher CI values were noted for the CP subjects compared to the controls, irrespective of speed or cocontraction site and there was a significant (p < 0.05) increase in CI values with increased walking speed for both CP and control subjects. Phasic analyses for 5% max EMG and 10% max EMG "on" thresholds demonstrated significant (p < 0.05) main effects for group (CP subjects had a longer time period of muscle activation than controls) and speed (muscles were active longer at 90% FWS than 3 km.h-1). The precise mechanisms by which cocontraction contributes toward abnormal gait and wasted mechanical energy require further research incorporating both electromyographic and kinematic analysis.

Adolescent↗

PubMed2003

Restoration of anterior cruciate ligament-hamstring reflex arc after anterior cruciate ligament reconstruction.

It has recently been emphasized that restoration of neuromuscular function contributes to dynamic stability of the anterior cruciate ligament (ACL) reconstructed knee. The existence of an ACL-hamstring reflex arc, one of the protective ligament-muscular pathways, has been revealed in normal human knees. Although reinnervation to the reconstructed ACL has been observed histologically, it remains unclear whether the ACL-hamstring reflex arc is reestablished. This study examined the existence of the ACL-hamstring reflex arc in ACL-reconstructed knees by analyzing the changes in the hamstring EMG elicited by electrical stimulation to the reconstructed ACL. The patellar tendon grafts transplanted as an ACL substitute in three patients were electrically stimulated via a bipolar wire electrode inserted arthroscopically. The surface EMG was monitored from the ipsilateral biceps femoris and semitendinosus. In two of the three patients the significantly increased EMG value of the biceps femoris was detected between 120 and 140 ms after the onset of electrical ACL stimulation. The increased EMG activity detected in the biceps femoris after the stimulation to the patellar tendon graft indicated reestablishment of the ACL-hamstring reflex arc in the ACL-reconstructed knee.

Adult↗

PubMedDate not supplied

Effect of hamstring and psoas lengthening on pelvic tilt in patients with spastic diplegic cerebral palsy.

The purpose of this study was to evaluate the effects of hamstring lengthenings and psoas recessions over the brim of the pelvis (OTB) on pelvic function in the gait of patients with spastic cerebral palsy. Seventy-three patients were divided into four groups based on surgical intervention: medial hamstrings (n = 37), medial and lateral hamstrings (n = 12), medial hamstrings with psoas OTB (n = 9), and medial and lateral hamstrings with psoas OTB (n = 15). Three-dimensional gait analysis was completed both before and approximately 1 year after surgery. When pelvic position in gait was normal or posterior of normal preoperatively, there was a significant increase in pelvic tilt (p < 0.05) when medial and lateral hamstrings were lengthened, irrespective of simultaneous psoas OTB surgery. Medial hamstrings alone, with or without simultaneous psoas OTB, did not result in a significant change in pelvic position, irrespective of preoperative pelvic position. The only surgical combination that caused a reduction in excessive preoperative anterior pelvic tilt was medial and lateral hamstrings with psoas OTB, a 4 degrees change of limited clinical significance. In general, psoas and medial hamstring surgery have minimal effect on the pelvic position during gait. Medial and lateral hamstring lengthening will increase pelvic tilt if preoperative pelvic position is normal or slightly posteriorly tilted. The results of this study suggest that the fundamental determinants of pelvic position during gait postoperatively are the extent of hamstring surgery (medial only vs. both medial and lateral hamstring lengthening) and the preoperative position of the pelvis.

Cerebral Palsy↗

PubMed2004

Arthroscopic anterior cruciate ligament reconstruction with periosteum-enveloping hamstring tendon graft.

Tendon-bone incorporation of a tendon graft within the bone tunnel is of priority concern when using for anterior cruciate ligament (ACL) reconstruction. Superior healing process and stronger healing strength can be achieved when periosteum is sutured on the tendon inserted into a bone tunnel. We applied this idea to ACL reconstruction for enhancing tendon graft-bone tunnel healing. This is a prospective clinical outcome study with this surgical technique at minimal 2 years follow-up. Periosteum-enveloping hamstring tendon graft has been used in 68 patients. Data from 62 patients who had been followed up completely were analyzed. All patients suffered from a grade 3 or higher grade of Lachman and anterior drawer test with a positive pivot-shift test. Clinical assessments included the Lysholm knee scores, International Knee Documentation Committee (IKDC) scores, KT-1000 instrumented testing, thigh muscle assessment, and radiographic evaluation. The median Lysholm knee score was 59 (40-70) and 94 (60-100) points (P<0.01) before and after surgery. After reconstruction, 81% of patients were able to return to moderate or strenuous activity. Four (6%) patients were found to exhibit grade 2 or more ligament laxity. Complete range of motion could be achieved in 86% of patients. Three patients (5%) had positive pivot shift. Finally, 92% of patients were assessed as normal or nearly normal rating by IKDC guideline. Bone tunnels enlargement of more than 1 mm was identified in 5% of femoral tunnels and 6% of tibial tunnels. The study shows that a satisfactory result can be achieved with the periosteum-enveloping hamstring tendon graft in ACL reconstruction. Periosteum can be easily harvested at the proximal tibia from a routine incision for hamstring tendon harvesting. Besides the potential for improving tendon-bone healing, enveloped periosteum may help to seal the intra-articular tunnel opening in the early postoperative period, and thus avoid synovial fluid reflux into the tunnel. Bone tunnel enlargement could be reduced.

Adolescent↗

PubMed2006

Effects of stretching on passive muscle tension and response to eccentric exercise.

BACKGROUND: Stretching is used in an attempt to improve performance and reduce the risk of muscle injury, with little evidence to support its effectiveness. HYPOTHESIS: Four weeks of static or ballistic stretching can attenuate the increased soreness and decreased flexibility seen after eccentric exercise. STUDY DESIGN: Controlled laboratory study. METHODS: Twenty-nine male subjects were randomly assigned to a static stretching, ballistic stretching, or control group. On each of 4 consecutive days, they completed 4 maximal range of motion stretches using a Cybex isokinetic dynamometer to passively stretch the hamstrings at 0.087 rad.s(-1) (5 deg.s(-1)). Stiffness from 0.87 to 1.48 rad (50 degrees -85 degrees ), peak range of motion, work absorption, peak resistive torque, and soreness were measured. Participants then completed 4 weeks of either static or ballistic stretching for a total stretching duration of 3600 seconds. After training, the 4 days of testing were repeated with an eccentric exercise task added after day 1. RESULTS: Stretching groups had an increase in range of motion and stretch tolerance after 4 weeks of stretching, with no change in muscle stiffness, work absorption, or delayed onset muscle soreness. After eccentric exercise, they also had greater range of motion and stretch tolerance than did controls. CONCLUSION: Both static stretching and ballistic stretching increase range of motion, most likely as a result of enhanced stretch tolerance rather than changes in muscle elasticity. Four weeks of stretching maintain range of motion and stretch tolerance in the days after eccentric exercise.

Adolescent↗

PubMed2004

Effect of acute static stretching on force, balance, reaction time, and movement time.

PURPOSE: The purpose of the study was to investigate the effect of an acute bout of lower limb static stretching on balance, proprioception, reaction, and movement time. METHODS: Sixteen subjects were tested before and after both a static stretching of the quadriceps, hamstrings, and plantar flexors or a similar duration control condition. The stretching protocol involved a 5-min cycle warm-up followed by three stretches to the point of discomfort of 45 s each with 15-s rest periods for each muscle group. Measurements included maximal voluntary isometric contraction (MVC) force of the leg extensors, static balance using a computerized wobble board, reaction and movement time of the dominant lower limb, and the ability to match 30% and 50% MVC forces with and without visual feedback. RESULTS: There were no significant differences in the decrease in MVC between the stretch and control conditions or in the ability to match submaximal forces. However, there was a significant (P < 0.009) decrease in balance scores with the stretch (decreasing 9.2%) compared with the control (increasing 17.3%) condition. Similarly, decreases in reaction (5.8%) and movement (5.7%) time with the control condition differed significantly (P < 0.01) from the stretch-induced increases of 4.0% and 1.9%, respectively. CONCLUSION: In conclusion, it appears that an acute bout of stretching impaired the warm-up effect achieved under control conditions with balance and reaction/movement time.

Adult↗

PubMed1987

Factors affecting selected reciprocal muscle group ratios in preadolescents.

This study examines the influence of limb velocity and lateral dominance on the relationship between the knee flexors and extensors. Thirty preadolescents, 18 male and 12 female, performed a series of reciprocal knee flexion-extension movements on the Cybex II isokinetic system. The tests were performed at a range of selected velocities and on both dominant and nondominant limbs. The agonist-antagonist ratios considered were the peak torque ratios, the torque ratio produced at specific angles, and the ratio comparing the total work performed by the hamstrings with that of the quadriceps. The results showed that an increased limb velocity produces a significant increase in the peak torque and work ratios (P less than 0.05), limb velocity has no significant effect on the torque ratio produced at 30 degrees and 60 degrees in the preadolescents, and lower limb lateral dominance has no significant effect on the three ratios examined.

Child↗

PubMedDate not supplied

Comparison of muscle strength and flexibility between the preferred and non-preferred leg in English soccer players.

Most soccer players have a favoured foot for kicking the ball, and it is believed that this preference may lead to an asymmetry in the strength and flexibility of the lower extremities. This study was designed to determine whether asymmetry in strength and flexibility are present in the legs of soccer players.Forty-one elite and sub-elite soccer players (age 23.4 +/- 3.8 years; height 1.81 +/- 0.06 m; body mass 81.7 +/- 9.9 kg) were studied (data are presented as mean +/- SD). The dynamic strength of knee flexors (hamstrings) and knee extensors (quadriceps) was measured using an isokinetic dynamometer at angular velocities of 1.05, 2.09, 5.23 rad/s (in a concentric mode) and 2.09 rad/s (in an eccentric mode). The concentric strength ratio (hamstrings(conc)/quadriceps(conc)) and the dynamic control ratio (hamstrings(ecc)/quadriceps(conc)) were computed. Hip joint flexibility (in flexion) was measured using a goniometer.A significant difference between the preferred and non-preferred leg was found in the knee flexors at 2.09 rad/s (119 +/- 22 versus 126 +/- 24 Nm; P < 0.05) and for the dynamic control ratio (0.79 +/- 0.13 versus 0.84 +/- 0.16 Nm; P < 0.05). In both cases the knee flexors of the preferred leg were weaker than those of the non-preferred leg. A total of 28 of the 41 players (68%) had significant musculoskeletal abnormality (imbalance >10%) in one or more specific muscle groups. No significant differences were found in flexibility of the hip joint between the preferred and non-preferred leg (P > 0.05). It is concluded that the lower strength of the knee flexor muscles of the preferred leg may be associated with the differential use of these muscle during the kicking action and thus constitutes a unique training effect associated with soccer. This in turn can lead to muscular imbalance which is generally regarded as an injury risk factor.

Adult↗

PubMed1998

The reliability and validity of a chair sit-and-reach test as a measure of hamstring flexibility in older adults.

The purpose of this study was to examine the test-retest reliability and the criterion validity of a newly developed chair sit-and-reach (CSR) test as a measure of hamstring flexibility in older adults CSR performance was also compared to sit-and-reach (SR) and back-saver sit-and-reach (BSR) measures of hamstring flexibility. To estimate reliability, 76 men and women (M age = 70.5 years) performed the CSR on 2 different days, 2-5 days apart. In the validity phase of the study, scores of 80 men and women (M age = 74.2 years) were obtained on three field test measures of hamstring flexibility (CSR, SR, and BSR) and on a criterion test (goniometer measurement of a passive straight-leg raise). Results indicate that the CSR has good intraclass test-retest reliability (R = .92 for men; r = .96 for women), and has a moderate-to-good relationship with the criterion measure (r = .76 for men; r = .81 for women). The criterion validity of the CSR for the male and female participants is comparable to that of the SR (r = .74 and r = .71, respectively) and BSR (r = .70 and r = .71, respectively). Results indicate that the CSR test produces reasonably accurate and stable measures of hamstring flexibility. In addition, it appears that the CSR is a safe and socially acceptable alternative to traditional floor sit-and-reach tests as a measure of hamstring flexibility in older adults.

Aged↗