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PubMed2003

Synergy of medial and lateral hamstrings at three positions of tibial rotation during maximum isometric knee flexion.

Rotation of the knee has been used to isolate the strength of the medial and lateral hamstrings during manual testing of the knee flexors. The purpose of this study was to determine if medial and lateral rotation of the knee during manual knee flexor strength testing increased the electromyographic activity of the respective hamstrings. Twenty-three women between 22 and 36 years old with no history of lower extremity injury or disease participated in the study. Indwelling fine wire electrodes were used to record EMG activity of the medial (semitendinosus and semimembranosus) and lateral (long and short heads of the biceps femoris) hamstring muscles during maximally resisted knee flexion with neutral, medial, and lateral rotation of the knee. Repeated measures analysis of variance with post hoc Bonferroni adjustments were used to compare EMG activity across the three tests. EMG activity increased significantly for the target hamstrings during ipsilateral rotation (P<0.05). The semitendinosus had a mean activity of 109% Max. during medial rotation as opposed to 95% Max. during lateral rotation. The semimembranosus averaged 107 and 89% Max. in medial and lateral rotation respectively. Conversely, both the long and short head of the biceps muscle showed significantly higher activity (P<0.05) during lateral compared to medial rotation (110 and 108% compared to 93 and 97%, respectively). Even though the differences are statistically significant they ranged from 2 to 13% only of maximum activity, the clinical importance of this small change in EMG activity is questionable.

Adult↗

PubMed1996

Stump length as related to atrophy and strength of the thigh muscles in trans-tibial amputees.

Stump length and the thigh muscles strength of the amputated limb are among the major factors influencing outcome of prosthetic rehabilitation of trans-tibial amputees. In the present study the authors evaluated and compared the strength of quadriceps and hamstrings muscles of both limbs in trans-tibial amputees, as measured by means of an electrical dynamometer. The obtained results showed that the thigh muscles of the sound limbs are significantly stronger than those of the amputated limbs (p < 0.01). The results obtained for amputees with shorter stumps were compared with those with longer stumps. In the group of amputees (n = 9) with a stump shorter than 15.1 cm, values of peak torque (in isokinetic contraction) and maximal average torque (in isometric contraction) were significantly (p < 0.5) weaker when compared to those (n = 9) with a stump longer than 15.1 cm. The results obtained for amputees with a higher rate of thigh muscle atrophy were compared to those with lesser atrophy. In the group of amputees where muscle atrophy was accompanied by decrease in thigh girth of over 5.9 cm, muscles strength did not significantly decrease (p < 0.5) as compared to amputees where thigh girth decrease was less than 5.9 cm. It is concluded that atrophy of the thigh muscles of trans-tibial amputees is accompanied with a significant decrease in strength. In amputees with a short stump, the short lever action provided by the stump interferes with the ability of the thigh muscles to control the prosthesis efficiently during daily activities such as standing and walking.

Activities of Daily Living↗

PubMed2000

Lower limb muscle activity in ambulatory children with cerebral palsy before and after the treatment with Botulinum toxin A.

Purpose: The study investigated the effect of Botulinum toxin A on the gait and lower limb muscle activity of ambulatory CP children. Methods: 19 spastic diplegic and 4 left hemiparetic CP children were injected with a mean dose of 23.5 units of Botulinum toxin A/kg body weight into the gastrocnemius and hamstring muscles. Muscle tone and gait analysis including the kinesiological electromyogram of the shank and thigh muscles were assessed before and four weeks after injection and compared with the help of a multivariate analysis (p < 0.05). Results: Botulinum toxin A caused a definite reduction of plantarflexor, knee and hip hypertonia in 21 children, resulting in a more plantar grade and erect gait in 17 children four weeks after injection. Gait analysis showed a statistically significant improvement in peak ankle dorsi-flexion and knee extension during stance, and the length of the force point of action under both feet increased. Electromyography revealed sig-nificantly less co-contraction of the lower leg muscles, due to a more phasic instead of a tonic activity of the tibialis anterior muscle, and an improved activation pattern of the left rectus and biceps femoris muscles. Conclusions: The present study demonstrated that the injection of Botulinum toxin A resulted in a more mature muscle activation pattern of CP children. Most of the children walked more plantigrade and erect, the functional gait parameters, however, did not change.

Journal Article↗

PubMed2000

The relationship between tight hamstrings and lumbar hypolordosis in children with cerebral palsy.

STUDY DESIGN: Retrospective clinical and radiographic review. OBJECTIVE: To assess the influence of tight hamstrings on the sagittal alignment of the thoracic and lumbar spine in children with cerebral palsy. SUMMARY OF BACKGROUND DATA: It is postulated that tight hamstrings may produce a hypolordosis of the lumbar spine. The abnormal sagittal contour of the spine may lead to increased stresses in the lumbar spine and subsequent pain and disability. This is of special concern in children with cerebral palsy who often have shortened spastic hamstring muscles. METHODS: Twenty-one patients were evaluated, with a mean age of 9.4 years. Standing and sitting lateral spine films were obtained and the lumbar lordosis and thoracic kyphosis were measured using the Cobb method. The popliteal angle was measured to assess hamstring tightness, such that a large popliteal angle indicates tight hamstrings. RESULTS: We found a statistically significant correlation between the sitting lumbar curve and popliteal angle (Pearson correlation value -0.77, P < 0.01). As the popliteal angle increased, the amount of lumbar lordosis decreased. This correlation was less significant when the patient was standing (Pearson correlation value -0.59). CONCLUSION: This study demonstrates that there is a correlation between tight hamstrings, as measured by the popliteal angle, and decreasing lumbar lordosis, especially when sitting.

Adolescent↗

PubMed1991

Serum creatine kinase activity and its changes after a muscle biopsy.

The significance of the absolute elevations of serum creatine kinase (CK) levels after intense exercise and injuries was studied by measuring CK activities from seven healthy active males during a 2-week period, with a muscle biopsy taken between the first and second week. Most of the subjects (three lifters and two runners) carried on their normal exercise activities, while two lifters stopped training during the 2 weeks. The weight of the biopsy, number of fibres, percentage of fibre types, and cross-sectional areas of the muscle fibres were measured. The CK levels of the non-active subjects and runners remained consistently low during the control week, whereas those of the lifters were usually 500% greater than those of the other two groups, and fluctuated with the intensity of their workouts. A muscle biopsy, having a mean weight of 71.3 mg and containing 1800 fibres, increased the CK values by approximately 100 units litre-1 (U l-1) in most of the subjects. One runner injured his right hamstring muscles 2 days prior to the biopsy, and his CK values rose from 50 to 4400 U l-1. The increases in CK after the biopsy were not related to fibre type, activity, weight of the biopsy, or number or size of fibres removed. These results indicate that: (1) CK values are consistently lower in normal subjects and runners than in lifters. (2) Weight training results in chronic elevations of CK. (3) Compared to a muscle biopsy, muscular injury dramatically increases CK levels. (4) Elevation of serum CK is observed as early as 1 h after an intense weight-lifting session.(ABSTRACT TRUNCATED AT 250 WORDS)

Biopsy, Needle↗

PubMed2006

Effect of defocused CO2 laser on equine tissue perfusion.

Treatment with defocused CO2 laser can have a therapeutic effect on equine injuries, but the mechanisms involved are unclear. A recent study has shown that laser causes an increase in equine superficial tissue temperature, which may result in an increase in blood perfusion and a stimulating effect on tissue regeneration. However, no studies have described the effects on equine tissue perfusion. The aim of the present study was to investigate the effect of defocused CO2 laser on blood perfusion and to correlate it with temperature in skin and underlying muscle in anaesthetized horses. Differences between clipped and unclipped haircoat were also assessed. Eight horses and two controls received CO2 laser treatment (91 J/cm2) in a randomised order, on a clipped and unclipped area of the hamstring muscles, respectively. The significant increase in clipped skin perfusion and temperature was on average 146.3 +/- 33.4 perfusion units (334%) and 5.5 +/- 1.5 degrees C, respectively. The significant increase in perfusion and temperature in unclipped skin were 80.6 +/- 20.4 perfusion units (264%) and 4.8 +/- 1.4 degrees C. No significant changes were seen in muscle perfusion or temperature. In conclusion, treatment with defocused CO2 laser causes a significant increase in skin perfusion, which is correlated to an increase in skin temperature.

Animals↗

PubMed1993

Functional changes of the sciatic nerve in mice chronically infected with Trypanosoma cruzi.

Early histological studies carried out in the sciatic nerve of mice chronically infected with Trypanosoma cruzi showed demyelination and scanty axonal degeneration. The experiments reported in this paper were designed to assess the functional state of the sciatic nerve and of some of the muscles it supplies. For these purposes 14 mice were infected with trypomastigotes (clon K-98, CA-I strain) 12 months before the investigation. Results were compared with 13 normal mice matched by age and weight. Hamstring muscles were studied electromyographically by means of a fine coaxial needle electrode and the sciatic nerve action potential characteristics were recorded with surface electrodes. All the experiments were carried out in vivo. In the infected mice the electromyogram showed that some motor unit potentials has enlarged amplitude and duration and increased number of phases, suggesting that the size of their territories had been enlarged, probably through axonal collateral sproutings and reinnervation of muscle fibers previously relinquished by their original innervation. The sciatic nerve action potential of the infected animals showed diminished amplitude and prolonged latency. These features signal reduced number of functional axons within the nerve and demyelination of the remaining conducting fibers. These findings are in line with the histological evidences of the involvement of the peripheral nervous system in Chagas disease and give additional information about the functional state of the peripheral nerves in the experimental model.

Action Potentials↗

PubMed2002

Age-related changes in the interactive mobility of the hip and knee joints: a geometrical analysis.

This study examined any systematic age-related change in the passive range of motion (PROM) of the hip and knee joints. Seventy-seven healthy male volunteers ranging in age from 15 to 73 years were assessed. A geometrical range of motion (ROM) analysis was applied, which could evaluate the effects of both monoarticular and biarticular muscles. The PROM of the hip joint decreased progressively with advancing age, whereas that of the knee joint remained unchanged. In addition, the interactive PROM of the hip and knee joint associated with biarticular rectus femoris and hamstring muscles also showed an age-related reduction. The progressive reduction of the ROM is probably caused by shortening of muscles or connective tissues due to reduced compliance of joint structures and degenerative changes in spinal alignment, as well as by diminished muscle stretching resulting from a decrease in daily physical activities with advancing age.

Adolescent↗

PubMed1985

Isokinetic measurements of muscle strength in hysterical paresis.

The torque during isokinetic knee extensions and flexions was determined in repeated tests at 3 speeds of angular rotation in 25 patients with pareses considered to be hysterical after relevant examinations and follow-up. The torque records were combined with surface EMG from the quadriceps and the hamstring muscles in some patients. Besides the weakness, 3 signs were observed that are not usually seen in patients with pareses due to verified peripheral or central lesions. These signs were: Enlarged variability of torque in repeated tests of the same movement (larger than 20% of maximum torque in 22 patients). Higher torque in fast movements than in slow movements (8 patients). Force production in knee flexion less than that expected from the weight of leg and lever arm due to restraining activation of the quadriceps muscle (12 patients). The restraint was present although there was no spasticity. The signs reflect inconsistent and contradictory motor performance that is not compatible with a genuine paresis. Thus, they aid the identification of weakness of functional origin.

Adult↗

PubMed1999

Influence of complete spinal cord injury on skeletal muscle cross-sectional area within the first 6 months of injury.

In this study we examined the influence of complete spinal cord injury (SCI) on affected skeletal muscle morphology within 6 months of SCI. Magnetic resonance (MR) images of the leg and thigh were taken as soon as patients were clinically stable, on average 6 weeks post injury, and 11 and 24 weeks after SCI to assess average muscle cross-sectional area (CSA). MR images were also taken from nine able-bodied controls at two time points separated from one another by 18 weeks. The controls showed no change in any variable over time. The patients showed differential atrophy (P = 0.0001) of the ankle plantar or dorsi flexor muscles. The average CSA of m. gastrocnemius and m. soleus decreased by 24% and 12%, respectively (P = 0.0001). The m. tibialis anterior CSA showed no change (P = 0.3644). As a result of this muscle-specific atrophy, the ratio of average CSA of m. gastrocnemius to m. soleus, m. gastrocnemius to m. tibialis anterior and m. soleus to m. tibialis anterior declined (P = 0.0001). The average CSA of m, quadriceps femoris, the hamstring muscle group and the adductor muscle group decreased by 16%, 14% and 16%, respectively (P< or =0.0045). No differential atrophy was observed among these thigh muscle groups, thus the ratio of their CSAs did not change (P = 0.6210). The average CSA of atrophied skeletal muscle in the patients was 45-80% of that of age- and weight-matched able-bodied controls 24 weeks after injury. In conclusion, the results of this study suggest that there is marked loss of contractile protein early after SCI which differs among affected skeletal muscles. While the mechanism(s) responsible for loss of muscle size are not clear, it is suggested that the development of muscular imbalance as well as diminution of muscle mass would compromise force potential early after SCI.

Adolescent↗

PubMed1981

Topical anesthesia: H-reflex recovery changes by desensitization of the skin.

The H-reflex recovery curve of the soleus muscle was studied in 53 normal subjects before and after the application of topical anesthesia (20% benzocaine) to various skin areas and dermatomes of the lower limb. Skin areas were those overlying the calf, tibialis anterior, quadriceps and hamstrings muscles, and the dermatomes were L2, L3, L4, L5, S1, S2. In 42 subjects the H-reflex initial recovery decreased by 10-80 msec with a mean of 20 +/- 17 msec 30 min after application of topical anesthesia. Also, the test reflex (the second sequential H-reflex) had a faster recovery with less inhibition than that before anesthesia. It was also noticed that the longer the inhibition period before anesthesia, the greater the decrease in recovery time. These observations had no correlation with the skin area or dermatome desensitized by the anesthesia. furthermore, these observations were not noted when a placebo was sprayed on the skin. The results from this study indicate that input from cutaneous afferents may have an important inhibitory effect on the alpha-motoneurons of the soleus muscle. This effect is possibly more profound on the large phasic motoneurons. These results are discussed in relation to clinical interpretations of the H-reflex recovery curves.

Adolescent↗

PubMed2005

How early reactions in the support limb contribute to balance recovery after tripping.

Tripping causes a forward angular momentum that has to be arrested to prevent a fall. The support limb, contralateral to the obstructed swing limb, can contribute to an adequate recovery by providing time and clearance for proper positioning of the recovery limb, and by restraining the angular momentum of the body during push-off. The present study investigated how such a contribution is achieved by the support limb in terms of response times and muscle moment generation, in order to provide more insight in the requirements for successful recovery after tripping. Twelve young adults repeatedly walked over a platform in which 21 obstacles were hidden. Each subject was tripped over one of these obstacles during mid-swing in at least five trials. Kinematics, dynamics and muscle activity were measured. Very rapid responses were seen in the muscles of the support limb (approximately 65 ms), causing fast increases in muscle moments in the joints during the primary phase of recovery. Especially a large ankle plantar flexion moment (204 Nm), a knee flexion moment (-54 Nm) and a hip extension moment (52 Nm), generated by triceps surae and hamstring muscle activity, brought about the necessary push-off reaction and simultaneously caused a restraining of the forward angular momentum of the body. These required joint moments could be a problem for the elderly, who might not be able to generate such powerful moments. Strength training in these muscle groups may be indicated in elderly subjects to reduce the risk of falling after a trip.

Accidental Falls↗

PubMed2006

Acute first-time hamstring strains during high-speed running: a longitudinal study including clinical and magnetic resonance imaging findings.

BACKGROUND: Hamstring muscle strain is one of the most common injuries in sports. Still, knowledge is limited about the progression of clinical and magnetic resonance imaging characteristics and their association with recovery time in athletes. HYPOTHESIS: Knowing the anatomical location and extent of an acute first-time hamstring strain in athletes is critical for the prognosis of recovery time. STUDY DESIGN: Case series (prognosis); Level of evidence, 2. METHODS: Eighteen elite sprinters with acute first-time hamstring strains were prospectively included in the study. All subjects were examined, clinically and with magnetic resonance imaging, on 4 occasions after injury: at day 2 to 4, 10, 21, and 42. The clinical follow-up period was 2 years. RESULTS: All sprinters were injured during competitive sprinting, and the primary injuries were all located in the long head of the biceps femoris muscle. There was an association between the time to return to pre-injury level (median, 16; range, 6-50 weeks) and the extent of the injury, as indicated by the magnetic resonance imaging parameters. Involvement of the proximal free tendon, as estimated by MRI, and proximity to the ischial tuberosity, as estimated both by palpation and magnetic resonance imaging, were associated with longer time to return to pre-injury level. CONCLUSION: Careful palpation during the first 3 weeks after injury and magnetic resonance imaging investigation performed during the first 6 weeks after injury provide valuable information that can be used to predict the time to return to pre-injury level of performance in elite sprinting.

Adolescent↗

PubMed1983

Reflex responses of human thigh muscles to non-noxious sural stimulation during stepping.

An investigation of reflex responses of leg muscles to sural stimulation during stepping was performed on human subjects. Non-noxious electrical stimulation applied during the swing phase or the latter half of the stance phase produced a mixed increase and decrease of EMG activity in the hamstring muscles. No response or very weak response was observed when the same stimulus was applied during either quiet standing or various levels of constant voluntary effort at varying hip and knee joint angles.

Adult↗

PubMed1998

The effects of serial stretch loading on stretch work and stretch-shorten cycle performance in the knee musculature.

Training methods to optimize stretch-shorten cycle performance and an active muscle's ability to resist a sudden stretch (stretch work) and the relationship between the two have not been fully explored. The purpose of this study was to examine the effects of an 8-week strengthening program of serial stretch loading on stretch work and stretch-shorten cycle performance in the quadriceps and hamstring muscles. Thirty-one asymptomatic subjects participated in pre- and post-tests of maximum voluntary isometric contractions, stretch work and stretch-shorten cycle trials, and single-leg vertical jumps. The training portion consisted of progressively resisted isotonic single-leg squats. One leg exercised against an isotonic load with serial stretch loading, while the other leg exercised against isotonic load alone. Training resulted in strength gains in both legs indicated by the increase in weight lifted during training, but not by maximum voluntary isometric contractions. Vertical jump height increased in both legs. In the hamstring, stretch work decreased and stretch-shorten cycle performance increased in both legs. In the quadriceps, serial stretch loading intervention resulted in increased stretch-shorten cycle performance and no significant change in stretch work. The correlation between stretch-shorten cycle and stretch work was weak but significant. These findings suggest that the use of serial stretch loading could improve muscular performance and enhance a muscle's potential for dynamic stabilization.

Adult↗

PubMed1990

Electromyographic analysis of postural adjustments in two methods of balance testing.

The primary purpose of this study was to compare postural responses during two methods of balance testing: 1) a platform perturbation test (PP), with destabilizing forces of uniform magnitude given at the base of support, and 2) a postural stress test (PST), with destabilizing forces of increasing magnitude given at the waist. A secondary purpose was to examine the relationship between balance strategy scores and the patterns of muscle responses as determined by electromyographic analysis on the PST. Postural responses to backward sway of 17 healthy subjects, aged 60 to 79 years (means = 69.0, s = 5.3), were characterized bilaterally by EMG recording of the tibialis anterior, quadriceps femoris, gastrocnemius, and hamstring muscles. We examined three measures of bilateral postural responses: 1) latency to first muscle response (FR) among the four lower extremity muscle groups, 2) tibialis anterior muscle latency (TA), and 3) patterns of muscle responses. Our results demonstrated significantly shorter (p less than .001) TAs and FRs (in milliseconds) on the PST than on the PP (PST TA: = means = 80.3, s = 12.4; PP TA: = means = 142.6, s = 13.4; PST FR: means = 75.9, s = 10.4; PP FR: = means = 140.4, s = 13.6). The ankle strategy was the most frequently used pattern of muscle response during both the PP and the PST, but it occurred less frequently on the PST than on the PP (PP = 72.5%, PST = 50.9%) (p less than .05). No consistent relationship was observed between the balance strategy scores as determined by videotape analysis of the PST and the patterns of muscle responses as determined by EMG analysis.

Aged↗

PubMed2000

Closed kinetic chain alone compared to combined open and closed kinetic chain exercises for quadriceps strengthening after anterior cruciate ligament reconstruction with respect to return to sports: a prospective matched follow-up study.

Rehabilitation after anterior cruciate ligament (ACL) reconstruction has focused over the past decade on closed kinetic chain (CKC) exercises due to presumably less strain on the graft than with isokinetic open kinetic chain exercises (OKC); however, recent reports suggest that there are only minor differences in ACL strain values between some CKC and OKC exercises. We studied anterior knee laxity, thigh muscle torque, and return to preinjury sports level in 44 patients with unilateral ACL; group 1 carried out quadriceps strengthening only with CKC while group 2 trained with CKC plus OKC exercises starting from week 6 after surgery. Anterior knee laxity was determined with a KT-1000 arthrometer; isokinetic concentric and eccentric quadriceps and hamstring muscle torque were studied with a Kin-Com dynamometer before and 6 months after surgery. At an average of 31 months after surgery the patients answered a questionnaire regarding their current knee function and physical activity/sports to determine the extent and timing of their recovery. No significant differences in anterior knee laxity were noted between the groups 6 months postsurgery. Patients in group 2 increased their quadriceps torque significantly more than those in group 1, but no differences were found in hamstring torque between the groups. A significantly higher number of patients in group 2 (n = 12) than in group 1 (n = 5) returned to sports at the same level as before the injury (P < 0.05). Patients from group 2 who returned to sports at the same level did so 2 months earlier than those in group 1. Thus the addition of OKC quadriceps training after ACL reconstruction results in a significantly better improvement in quadriceps torque without reducing knee joint stability at 6 months and also leads to a significantly higher number of athletes returning to their previous activity earlier and at the same level as before injury.

Adolescent↗

PubMed1992

A clinical trial of strengthening and aerobic exercise to improve gait and balance in elderly male nursing home residents.

The purpose of this study was to determine whether a moderate to high intensity strengthening and aerobic exercise program can improve the strength, exercise capacity, gait and balance of deconditioned male nursing home residents. Ambulatory subjects who scored 30 or less on the modified Tinetti gait and balance assessment scale, who demonstrated less than 80% of age-matched lower extremity strength on isokinetic muscle testing and who gave informed consent were enrolled. Subjects were randomized to either an exercise (n = 8) or a control (n = 6) group. All participants underwent an exercise test to determine maximal oxygen uptake (VO2max) and received quantitative gait and balance measurements. The subjects assigned to the exercise group than completed a 12-wk program of weight training for the lower extremities and stationary cycling. Both the exercise and control groups were then retested. Ten outcome variables were assessed: Tinetti mobility scores, VO2max, isokinetic-tested lower extremity strength and endurance, stride length, gait velocity, stance time, gait duration, cadence and balance. The exercise group, after completion of the program, demonstrated significant improvements in Tinetti mobility scores (P < 0.05), combined right and left quadricep muscle strength (P < 0.01), right and left lower extremity muscular endurance (P < 0.01), left stride length and gait velocity (P < 0.05), although other outcome variables changed insignificantly. The control group revealed no changes of significance with the exception of improvement of the combined right and left hamstring muscle strength (P < 0.05). Nevertheless, for those outcome variables that had improved significantly in the exercise group, the changes amounted to only a 5 to 10% increase over the baseline measurements. These findings showed that an appropriately designed high intensity exercise program can result in significant although limited improvements for clinical mobility scores, strength, muscular endurance and certain gait parameters.

Aged↗