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At least 73 records · Page 4Linked to original sources

PubMed1990

Differential responses to proprioceptive neuromuscular facilitation (PNF) stretch techniques.

The purpose of this study was to investigate the effects of sustained stretch and two common proprioceptive neuromuscular facilitation (PNF) stretch techniques on hamstring muscle activation and knee extension range of motion (ROM) in different athletic populations. Three stretch techniques: stretch-relax (SR), contract-relax (CR), and agonist contract-relax (ACR) were applied to 10 endurance athletes (EN), 10 high intensity athletes (HI), and 10 control subjects (C). The results revealed that ACR produced 89-110% greater hamstring EMG activity (P less than 0.05) and 9-13% more knee joint ROM than CR and SR, respectively. This same pattern was evident for the individual subject groups. Comparisons of mean data among the three subject groups revealed that the EN athletes generated 58-113% more hamstring EMG activity (P less than 0.05) than the HI and C groups, respectively, across all stretch conditions, whereas the EN group attained significantly less ROM than the HI and C groups for CR and ACR conditions. It was postulated that high intensity-short term activity training necessitates less hamstring resistance to knee extension than long term endurance training. The findings suggest that decreases in muscle activity may not be strongly related to increases in joint range of motion and that factors other than muscle relaxation are important in achieving increased ROM. Also, the differential effects of various stretch techniques between dissimilar athletic populations should be considered if stretch-induced injury is to be avoided.

Adult↗

PubMed1988

Ankle muscle activity during gait in children with cerebral palsy and equinovarus deformity.

Temporal electromyographic (EMG) characteristics of lower limb muscles during gait of spastic hemiplegic and diplegic children with cerebral palsy are described. All subjects were referred for presurgical evaluation of equinovarus deformity. The data indicated both similar and discriminating phasic EMG characteristics between groups of patients. All children displayed premature triceps surae activity beginning in swing phase of gait and continuing through stance. Tibialis posterior, normally active during stance, was also active during swing phase of gait. However, some patients displayed cocontraction of triceps surae and tibialis anterior during stance, together with hamstring muscle activity within normal limits. The remainder of the patients displayed a prolonged duration of hamstring activity. How this gait analysis contributed to presurgical decisions for equinovarus gait is discussed and compared with data from postsurgical gait analysis.

Ankle↗

PubMed1992

Effect of knee joint laxity on long-loop postural reflexes: evidence for a human capsular-hamstring reflex.

The onset latency and discharge amplitude of preprogrammed postural responses were evaluated in order to determine if the structure of synergistic activation could be altered by ligamentous laxity at the knee joint. Twelve subjects with unilateral and one subject with bilateral anterior cruciate ligament (ACL) insufficiency were tested while standing on a moveable platform. External balance perturbations (6 cm anterior or posterior horizontal displacements of the platform) were presented at velocities ranging from 15 to 35 cm/s. Perturbations were presented under the following experimental conditions: unilateral and bilateral stance, knees fully straight or flexed, and with ankle motion restricted or free. These stance, knee position, and ankle motion conditions were introduced to alter the stress transmitted to the knee joint during movement of the support surface. The automatic postural response was recorded from the tibialis anterior (T), quadriceps (Q), and medial hamstrings muscles (H) bilaterally. The normal response to an externally induced backward sway involved the automatic activation of T and Q at latencies of 80 ms and 90 ms respectively. Activation of the hamstrings in the non-injured extremity was not coupled with the postural response. Hamstrings are not typically involved in the correction posterior sway because H activation would tend to pull the center of mass further backwards. However, when the response in the ACL-deficient extremity was compared to the non-injured limb: (1) the automatic postural response in the ACL-deficient extremity was restructured to include hamstrings activation (100 ms latency), (2) H activation time was faster and less variable in the ACL-deficient limb, and (3) the ratio of H/Q discharge amplitude integrated over 100 ms and 200 ms from the onset of EMG activation showed a dominance of hamstring activity during unilateral stance on the lax limb. In addition, H/Q ratios integrated over 200 ms showed dominant hamstring activity in the ACL-deficient limb during bilateral stance. (4) Cross-limb comparisons showed greater normalized IEMG amplitudes for T, H, and Q during unilateral stance on the lax limb. These results suggest that a capsular-hamstring reflex is integrated into the existing structure of a preprogrammed postural synergy in order to compensate for ligamentous laxity. Furthermore, the generalized increase of response gain observed during perturbations of unilateral stance on the lax limb indicates that joint afference can modulate central programming to control localized joint hypermobility. A concept of postural control is discussed with respect to the capsular reflex, joint loading and displacement of the center of gravity.

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↗

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↗

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↗

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↗

PubMed1989

A sequential study of the peripheral nervous system involvement in experimental Chagas' disease.

To search for the sequential compromise of the spinal cord, nerves, and skeletal muscle in mice chronically infected with Trypanosoma cruzi, animals were subjected to electromyographic investigation, end-plate recordings, and histological studies at 7, 15, 37, 60, 90, 120, 180, 270, and 360 days postinfection. Electromyographic studies showed signs of motor unit remodeling as early as 15 days postinfection, when diminished duration and amplitude of motor unit potentials pointing to a primary muscle involvement were found. Thereafter, certain features of denervation, reinnervation, and primary muscle involvement were often found to coexist. Low miniature end-plate potentials with normal frequency and acetylcholine quantum content were found in end-plate recordings made at the phrenic-diaphragm in vitro. Double end-plate potentials were observed in most of the tested muscle fibers from day 90 postinfection. All these features suggest post-synaptic damage of the end-plate and the presence of reinnervation after day 90 postinfection. Histological studies disclosed inflammatory infiltrates consisting of lymphocytes and macrophages, with vasculitis as the main lesion in the hamstring muscles; intracellular parasites were seen in 25% of the cases. Neuropathic features, as expressed by type fiber grouping and grouped muscle fiber atrophy, were found. On nerve examination epineural, perineural, and endoneural vasculitis were seen. Digestion chambers and myelin ovoids (axonal degeneration) were observed. In teased fiber preparations, segmental internodal and paranodal demyelination and remyelination were found. The lumbar inflammatory spinal cord failed to show grey or white matter infiltrates. However, spinal roots and dorsal root ganglia were densely affected by inflammatory cells.

Animals↗

PubMed1988

Ventilatory and PaCO2 responses to voluntary and electrically induced leg exercise.

We studied the role of central command mediation of exercise hyperpnea by comparing the ventilatory and arterial CO2 partial pressure (PaCO2) responses to voluntary (ExV) and electrically induced (ExE) muscle contractions in normal, awake human subjects. We hypothesized that if central command signals are critical to a normal ventilatory response, then ExE should cause a slower ventilatory response resulting in hypercapnia at the onset of exercise. ExE was induced through surface electrodes placed over the quadriceps and hamstring muscles. ExE and ExV produced leg extension (40/min) against a spring load that increased CO2 production (VCO2) 100-1,000 ml/min above resting level. PaCO2 and arterial pH during work transitions and in the steady state did not differ significantly from rest (P greater than 0.05) or between ExE and ExV. The temporal pattern of ventilation, tidal volume, breathing frequency, and inspired and expired times, and the ventilation-VCO2 relationship were similar between ExE and ExV. We conclude that since central command was reduced and/or eliminated by ExE, central command is not requisite for the precise matching of alveolar ventilation to increases in VCO2 during low-intensity muscle contractions.

Adult↗

PubMedDate not supplied

Assessment of quadriceps/hamstring strength, knee ligament stability, functional and sports activity levels five years after anterior cruciate ligament reconstruction.

The purpose of this study was to examine individuals 5 years after ACL reconstruction and analyze changes involving strength, stability, function, and sports activities. Nineteen males and six females, mean age = 31.4 +/- 7.31 years, participated in this study. Fifteen subjects had received extraarticular and ten subjects had received intraarticular ACL reconstructions. Subjects completed a 100 point subjective functional activity questionnaire and a sports participation survey. Knee ligament stability was assessed during an objective knee examination. Isokinetic quadriceps and hamstring muscle strength were tested at 240 and 120 deg/sec using the Cybex II dynamometer. Anterolateral rotatory instability and positive Lachman were elicited on the operated leg for 80% of the subjects. No significant relationship was found between objective instability and the functional activity score. For the intraarticular group, a significant correlation (P less than 0.05) was found between increased quadriceps and hamstring strength on the operated leg and return to functional activities. Subjects' functional activity score was positively correlated (P less than 0.001) with their ability to participate in sports. Subjects participating in sports involving cutting and twisting motions were less successful in returning to their preinjury participation levels and reported more subjective complaints of pain, swelling, and/or instability. These results indicate that long-term progressive rehabilitation emphasizing increased quadriceps and hamstring strength to approximate the nonoperated leg may enhance successful return to functional and sports activities after ACL reconstruction.

Adult↗

PubMedDate not supplied

Normal ranges of popliteal angle in children.

Measurement of the popliteal angle is used to assess hamstring contracture in children with cerebral palsy. The popliteal angle in 482 normal children, 1-10 years of age, was measured. Using a 360 degrees goniometer, the popliteal angle was measured with the hip held at 90 degrees flexion to indicate hamstring muscle tightness. Between the ages of 1 and 3 years, the mean angle was 6 degrees (range, 0-15). At age 4, the angle rose to 17 degrees in girls and 27 degrees in boys (range, 5-45). At greater than or equal to 5 years the mean angle was 26 degrees with little change (range, 0-50). A popliteal angle of greater than 50 degrees in the above age groups indicates abnormal hamstring tightness.

Cerebral Palsy↗

PubMed1991

Effects of massage on alpha motoneuron excitability.

The purpose of this study was to investigate the specificity of the effects of massage (petrissage) on spinal motoneuron excitability as measured by changes in the peak-to-peak amplitude of H-reflex recordings. H-reflexes (and M-responses) were recorded from the distal aspects of the right triceps surae muscle of 8 men and 8 women, aged 20 to 37 years, with no neuromuscular impairments of the lower extremities. The H-reflexes were recorded during five control and four experimental conditions (20 trials at each condition). The control conditions (C1-C5) preceded and followed each experimental condition, providing a measure of the stability of the H-reflex. Each experimental condition consisted of a 4-minute period of massage of the ipsilateral and contralateral triceps surae and hamstring muscle groups (ITS, CTS, IHS, and CHS, respectively). The mean peak-to-peak amplitude of the H-reflex was found to be stable (range = 1.91-1.95 mV) across the five control conditions. H-reflex amplitudes recorded during the experimental conditions indicate that massage of the ITS resulted in a reduction of the H-reflex (0.83 mV) in comparison with the pretest control condition (C1) and the remaining experimental conditions (range = 1.77-2.23 mV). This difference was significant, and subsequent Newman-Keuls tests indicated a specificity of the effects of massage on the muscle group being massaged. [Sullivan SJ, Williams LRT, Seaborne DE, Morelli M. Effects of massage on alpha motoneuron excitability.

Adult↗

PubMed1988

Is the hyperpnea of muscular contractions critically dependent on spinal afferents?

We studied the role of spinal afferent pathways in the hyperpnea of electrically induced muscle contractions (ExE). The ventilatory (VE) and arterial CO2 partial pressure (PaCO2) responses were measured at rest and during two levels of ExE in awake human paraplegic subjects with clinically complete lesions of the spinal cord (range T4-T11). We hypothesized that if peripheral neural drive is critical to a normal ventilatory response, then ExE in the absence of intact pathways should cause a lower ventilatory response resulting in hypercapnia at the onset of ExE. ExE was induced by stimulation of the quadriceps and hamstring muscles that approximately doubled the resting level of CO2 production (VCO2). PaCO2 during work transitions and in the latter stages of ExE did not differ significantly from that at rest. Arterial pH progressively declined over time during ExE (P less than 0.01) as a result of increased lactate concentration (P less than 0.01). The linear relationship between VE and VCO2 was similar to that found for normal human subjects during ExE (P = 0.73). These data suggest that VE and presumably alveolar ventilation (VA) can be appropriately matched to VCO2 during low-intensity muscle contractions of the lower extremities in the absence of intact spinal afferent pathways. Moreover, since it is unlikely that postulated "central command" mechanisms were initiated during ExE in these paraplegic subjects, the data provide support for our previous conclusion that central command is not obligatory for matching VA to VCO2 (J. Appl. Physiol. 64: 218-225, 1988).

Adult↗

PubMed1988

Intrathecal galanin at low doses increases spinal reflex excitability in rats more to thermal than mechanical stimuli.

The neuropeptide galanin (GAL) was injected intrathecally (i.t.) in decerebrate, spinalized, unanesthetized rats and its effect on the nocifensive flexor reflex was examined. The reflex, which was evoked by intense mechanical or thermal stimulation of the foot, was recorded from the ipsilateral hamstring muscles. I.t. GAL increased reflex excitability significantly more to thermal than to mechanical stimuli. It is suggested that GAL, which is present in sensory fibers that innervate the skin, is released by the central terminals of cutaneous afferents that are much more sensitive to thermal than to mechanical stimuli.

Animals↗

PubMed1992

The effect of training on endurance and the cardiovascular responses of individuals with paraplegia during dynamic exercise induced by functional electrical stimulation.

Endurance for dynamic exercise, cardiac output, blood pressure, heart rate, ventilation, and oxygen consumption was measured in eight individuals with paraplegia at the end of 4-min bouts of exercise on a friction braked cycle ergometer. Movement of the subjects' legs was induced by electrically stimulating the quadriceps, gluteus maximus and hamstring muscles with a computer-controlled biphasic square--wave current at a frequency of 30 Hz. The friction braked cycle ergometer was pedalled at work rates which varied between 0 and 40 W. Measurements were repeated after 3 and 6 months to assess the affect of training. After 3 months of training it was found that endurance increased from 8 min at a work rate of 0 W to 30 min at a work rate of 40 W. Compared to the cardiovascular responses in non-paralyzed subjects, computerized cycle ergometry was found to be associated with higher relative stresses for a given level of absolute work. Mean blood pressure, for example, increased by over 30% during maximal work in individuals with paralysis compared to the typical response obtained for able-bodied subjects. Analysis of the data showed that instead of the 20-30% metabolic efficiency commonly reported for cycle ergometry, the calculated metabolic efficiency during computer-controlled cycle ergometry was only 3.6%.

Adult↗

PubMed1992

Spinal substance P and N-methyl-D-aspartate receptors are coactivated in the induction of central sensitization of the nociceptive flexor reflex.

We have studied the effects and interactions of the neurokinin-1 receptor antagonist CP-96,345 and the N-methyl-D-aspartate receptor/channel blocker MK-801, both applied intravenously, on the flexor reflex and on the facilitation of the flexor reflex by conditioning stimulation of cutaneous C-afferents in decerebrate, spinalized, unanesthetized rats. The flexor reflex was evoked by subcutaneous electrical stimuli applied to the sural nerve innervation area 1/min at an intensity that activated C-fibers and was recorded as electromyogram from the ipsilateral hamstring muscles. The magnitude of the baseline flexor reflex was usually highly stable in the course of the experiments without experimental manipulations. The same stimulus was used as a conditioning train (0.9 Hz, 20 shocks) and caused a brief facilitation of the flexor reflex, which was maximal 0.5 and 1 min after stimulation (255.1 +/- 23.6% over baseline). During the course of the conditioning stimulus train, the reflex magnitude was gradually increased (wind-up). MK-801 (0.1 and 0.5 mg/kg) consistently depressed the polysynaptic flexor reflex. At a dose of 0.5 mg/kg, but not 0.1 mg/kg, MK-801 reduced the wind-up and blocked the facilitation of the flexor reflex induced by the conditioning stimulus by 90%. The facilitatory effect of 7 pmol intrathecal substance P was also partially reduced by MK-801. CP 96,345 (1 and 3 mg/kg) did not depress the flexor reflex, but dose-dependently antagonized reflex facilitation by the conditioning stimulus train, similarly to its antagonism of intrathecally applied 7 pmol substance P-induced facilitation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1987

Optimal duration of static stretching exercises for improvement of coxo-femoral flexibility.

The purpose of this study was to determine the effect of different durations of static stretching exercises on coxo-femoral (hip) flexibility. The experimental group, consisting of 20 sedentary women (20-30 years of age), participated in an exercise programme of static stretching exercises with emphasis on the hamstring muscles. The programme lasted for 10 weeks and consisted of two 50-min sessions per week. A control group of 15 sedentary women did not participate in the programme. Hip flexibility was determined before, during and at the end of the programme by means of a goniometric measuring technique developed by us and described elsewhere. Three sub-groups were formed, each following the same programme except that the duration of the static stretch differed (group 1, 10 s; group 2, 20 s; group 3, 30 s). The ANOVA tests showed that for all groups - the control group excepted - the hip flexibility had improved significantly after 10 weeks (P less than 0.05). No significant differences in hip flexibility were noted between the three subgroups at the end of the programme. This finding suggests that a duration of 10 s static stretching is sufficient for improving coxo-femoral flexibility.

Adult↗

PubMed1987

High intensity electrical stimulation effect on thigh musculature during immobilization for knee sprain. A case report.

We conducted high intensity electrical stimulation of the quadriceps femoris and hamstring muscle groups daily during a three-week period of lower extremity cast immobilization for an athlete who sustained Grade II medial collateral and anterior cruciate ligament sprains. Thigh muscle hypertrophy of the injured (stimulated) leg was suggested by an increase in girth measurement on the day of cast removal. Three weeks after cast removal, single-leg, vertical-leap height was 92% of that accomplished by the dominant, uninjured leg, and the patient was able to return to athletic competition. This case report documents the usefulness of high intensity electrical stimulation for maintaining limb motor function during cast immobilization. Limb stabilization during stimulation and simultaneous excitation of agonist-antagonist muscle pairs also are discussed.

Adolescent↗