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PubMed1992

Isokinetic exercise system modification for short below-the-knee residual limbs.

The use of isokinetic exercise has been shown to be an effective way of strengthening debilitated muscles. In the below the knee amputee, significant quadriceps and hamstring muscle wasting has been documented. Although isokinetic strengthening of the debilitated knee extensors and flexors in the below the knee amputee would be beneficial, there are no fully described isokinetic equipment modifications in literature that would allow a short below the knee amputee to effectively use isokinetic equipment. This article describes such a modification.

Adult↗

PubMed1992

Vestibular-evoked postural reactions in man and modulation of transmission in spinal reflex pathways.

1. The effects of galvanic stimulation of the vestibular apparatus (with electrodes on the mastoid processes) have been studied in standing human subjects. With the head turned to one side, subjects swayed towards the anode. 2. Forwards sway was preceded by electromyographic (EMG) activity in quadriceps and tibialis anterior muscles. Backwards sway was preceded by EMG activity in soleus and hamstring muscles. 3. Using the method of H reflex conditioning, forward sway was found to be preceded by inhibition of soleus motoneurones. 4. Interaction between the vestibular-evoked inhibition of soleus motoneurones preceding forwards sway and peripheral reflex inhibition was examined by a spatial facilitation method. 5. Interaction was found between vestibular-evoked inhibition and Ia reciprocal, group I non-reciprocal and group Ia-Ia presynaptic inhibitory pathways. It is concluded that vestibular signals converge on spinal interneurones subserving these inhibitory actions. 6. A 'decoupling' of soleus motoneurons and soleus-coupled Renshaw cells was found in the period of soleus activation preceding backwards sway.

Adult↗

PubMed1992

Differential muscle strength decline in osteoarthritis of the knee. A developing hypothesis.

The ratio of quadriceps to hamstrings muscle strength (Q/H ratio) is important for the stability of the knee and for protection from excessive stress. The purpose of this study was to explore whether the Q/H ratio is altered in patients with osteoarthritis (OA). Subjects were 43 patients with physician-diagnosed OA of the knee (mean age, 65.61 years; SD, 12.74). Isometric knee flexor and extensor strength was measured with a hand-held dynamometer. Both muscle groups were weak, with relatively greater weakness in the quadriceps muscles. The mean Q/H ratio of 1.43 (SD, 0.39) was below ratios reported for young healthy adults (2.0). The low Q/H ratio might be caused by the inability to correct the measurement for gravity, but a liberal estimate of gravity correction raised the ratio only to 1.71 (SD, 0.47). The low Q/H ratio was probably not caused by physiologic changes due to aging, because the correlation between the ratio and age was low (-0.04). Since the correlation of the Q/H ratio with the usual level of pain (measured by a visual analogue scale) was negative (-0.26), the low ratio might be explained by reflex inhibition due to pain associated with disease.

Adult↗

PubMed1991

In vivo analysis of intracellular thallium-201 accumulation in skeletal muscle of the rat.

The specific accumulation of the K(+)-analogue Tl+ (201Tl+) in muscle after intramuscular injection was analysed by gamma spectrometry in vivo of rat hamstring muscles. A mixture (0.1 ml) of 201Tl+ (thallous+ chloride-) and 99mTc-pertechnetate- (Na+ pertechnetate-) was given, by which 99mTc-pertechnetate- served as a reference substance with negligible intracellular accumulation. After 30 min 8.9 +/- 5.8% of injected 99mTc-pertechnetate- remained in the muscle and 49 +/- 10% of 201Tl+ (+/- SD, n = 18). The difference between 201Tl+ and 99mTc-pertechnetate- at 30 min was taken as a measure of the intracellular 201Tl+ accumulation, which was 40% of the initial amount of 201Tl+. The half-time of the calculated intracellular 201Tl+ accumulation was 4.9 +/- 1.9 min. In the presence of ouabain (1.0 mM in the injectate) the intracellular 201Tl+ accumulation was 25 +/- 10% (n = 7), that is ouabain decreased the intracellular 201Tl+ accumulation by 38% (P = 0.0035). Non-radioactive Tl+ (1.0 mM Tl-acetate in the injectate) inhibited the uptake by 35% (P = 0.0013). Ouabain did not significantly affect the half-time for the Tl+ uptake. An increase in [K+] of the injectate from 0 to 5 mM had no significant effect. Insulin (0.2 units in the injectate) had no effect. It is concluded that the specific Tl(+)-accumulating properties of muscle fibres can be studied with the present in vivo technique, which can provide information about the Na-K-ATPase activity and the membrane potential of muscle fibres.

Animals↗

PubMed1979

The morphogenesis of the thigh of the mouse with special reference to tetrapod muscle homologies.

In order to provide an ontogenetic basis for the establishment of tetrapod muscle homologies and for the analysis of complex mammalian muscle states, a descriptive analysis of the morphogenesis of the thigh of Mus musculus has been made. The pattern and sequence of muscle cleavage and the migrations of individual muscle primordia are characterized from the eleventh day of gestation, when cleavage begins, through early neonatal stages. Observations on skeletal differentiation and lumbosacral plexus formation are also included. Thigh muscle morphogenesis is compared to that in the lizard, Lacerta, (Romer, '42) and the chick (Romer, '27) and homologies identified. An onogenetic basis for the definition of ancestral and derived muscle states is provided in muscles that are morphologically variable in mammals. These include the gluteus minimus, gracilis, adductor brevis and several hamstring muscles. Certain muscles that show variable innervation patterns in adult mammals, i.e., pectineus, quadratus and adductor magnus, typically develop from premuscle regions that separate muscle anlagen innervated by different nerves. Two muscle anlagen appear in the embryonic mouse thigh and then disappear late in prenatal or early postnatal development. Comparisons with other mammals, especially the marsupial, Marmosa, reveal that these muscles are phylogenetic vestiges that degenerate before maturity. A sartorius vestige is identifiable through the thirteenth day of gestation. A tenuissimus anlage is present until shortly after birth and is clearly innervated by a branch of the peroneal nerve.

Animals↗

PubMed1992

Development of anticipatory postural adjustments during locomotion in children.

1. Anticipatory postural adjustments were studied in children (6-14 yr of age) walking on a treadmill while pulling a handle. Electromyographs (EMGs) and movements were recorded from the left arm and leg. 2. Postural activity in the leg muscles preceded voluntary arm muscle activity in all age groups, including the youngest children (6 yr of age). The latency to both leg and arm muscle activity, from a triggering audio signal, decreased with age. 3. In older children the latency to both voluntary and postural activity was influenced by the phase of the step cycle. The shortest latency to the first activated postural muscle occurred during single support phase in combination with a long latency to arm muscle activity. 4. In the youngest children, there was no phase-dependent modulation of the latency to the activation of the postural muscles. The voluntary activity was delayed during the beginning of the support phase resulting in a long delay between leg and arm muscle activity. 5. The postural muscle activation pattern was modified in a phase-dependent manner in all children. Lateral gastrocnemius (LG) and hamstring muscles (HAM) were activated during the early support phase, whereas tibialis anterior (TA) and quadriceps (Q) muscles were activated during the late support phase and during the swing phase. However, in the 6-yr-old children, LG was also activated in the swing phase. LG was activated before the HAM activity in the youngest children but after HAM in 14-yr-old children and adults. 6. The occurrence of LG activity in postural responses before heel strike suggests an immature (nonplantigrade) gating of postural activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1992

Viscoelastic stress relaxation in human skeletal muscle.

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

Adult↗

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↗

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↗

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↗

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↗

PubMed1992

The management of decubitus ulcers by musculocutaneous flaps: a five-year experience.

Large decubitus ulcers can be treated by using many methods, including musculocutaneous flaps. Musculocutaneous flaps provide reliable, well-vascularized cover and often can be revised in patients with secondary recurrence. We have treated 30 patients with large decubitus ulcers during a 5-year period by using musculocutaneous advancement flaps of the gluteus maximus, the hamstring muscle, and the tensor fasciae latae. There were two complications treated by debridement with flap advancement in 1 patient and the use of another flap in the second patient. Four patients developed a recurrent ulcer, which was treated by reelevation and advancement of the original flap in all patients. The general management and overall results are presented.

Buttocks↗

PubMed1976

Fresh and cultured thyroid gland: survival and function after implantation.

Isogeneic or allogeneic thyroid glands were implanted into thyroidectomized recipeint rats. These grafts, either fresh or cultured, were placed in hamstring muscle pocket or under the renal capsule. Survival and function of the grafts were evaluated by: restoration of normal levels of serum thyroxine, weight gain, kidney transamidinase (a thyroxine-induced enzyme), and histological appearance of re-excised implants. A isografts, fresh and cultured, functioned well as ectopic thyroid glands, though restoration of normal serum thyroxine levels was more rapid for the fresh implants. Fresh allografts functioned transiently but then failed due to rejection. No function was detected for cultured allografts, and rejection was seen histologically. The rat thyroid allograft therefore differs from the rat parathyroid allograft, which often can function for several months despite histological evidence of rejection. Maintenance in tissue culture prior to implantation does not appear to alter the longterm immunogenicity of either organ.

Amidinotransferases↗

PubMed1976

The treatment of intoed gait in spina bifida patients by lateral transfer of the medial hamstrings.

The operation of lateral transfer of the medial hamstring muscles is described. Its applicating in the management of intoed gait in spina bifida is discussed, and the results of eight such operations, performed on four children, are recorded. The operation was effective in correcting the intoed gait in all; however, there was no activity in the transferred muscles in one child.

Child, Preschool↗

PubMed1992

Intrathecal neurokinin A facilitates the spinal nociceptive flexor reflex evoked by thermal and mechanical stimuli and synergistically interacts with substance P.

The neuropeptide neurokinin A was injected intrathecally and its effect on the spinal nociceptive flexor reflex was examined. The reflex, which was evoked by electrical, thermal or mechanical stimulation of the foot and was recorded from the ipsilateral hamstring muscles, was substantially facilitated by 7 pmol intrathecally injected neurokinin A. The facilitatory effect of neurokinin A to thermal stimulation was, however, significantly stronger than to electrical or mechanical stimuli. Furthermore, co-administration of neurokinin A with substance P induced a significant synergistic facilitation of the reflex. It is suggested that neurokinin A, like substance P, may be released in association with activation of polymodal C-nociceptors.

Animals↗

PubMed1977

C0-contraction and stretch reflexes in spasticity during treatment with baclofen.

Surface electromyograms were recorded from the quadriceps and hamstring muscles of 11 spastic patients during cyclical flexion and extension movements of the knee. A potentiometer strapped to the knee recorded the angle of the joint, the output signal being displayed on an oscilloscope. The patient used this signal to track a sine wave target for 20 cycles. The observer then moved the patient's limb through a further 20 cycles tracking the same target. Recordings were repeated at intervals for four hours after an oral dose of baclofen. Analysis of the recordings showed that the response of a spastic muscle to lengthening is not the same during passive movement as during voluntary movement. In mild spasticity stretch reflexes appear to be suppressed by voluntary effort whereas in severe spasticity they are enhanced. Baclofen suppressed the response to passive stretch by over 30% at plasma concentrations of over 250 ng/ml and by 50% at concentrations of over 400 ng/ml, but this effect was largely extinguised during voluntary movement.

Adolescent↗

PubMed1976

Synchronization of respiratory frequency by somatic afferent stimulation.

In cats anesthetized with chloralose-urethan, vagotomized, paralyzed, and artifically ventilated, superficial radial (cutaneous) and hamstring (muscle) nerve afferents were stimulated while phrenic nerve electrical activity was recorded. The results obtained with both types of nerves were similar. Stimulation in mid and late expiration advanced the onset of the next inspiration, shortening its duration. Stimulation in early inspiration advanced, while that in late inspiration delayed, the onset of the next expiration. These effects were often accompanied by changes in phrenic motoneuron firing patterns (earlier recruitment, increased discharge frequency, increased slope of integrated phrenic neurogram). Repetitive somatic afferent stimulation produced sustained increases in respiratory frequency in all cats and in half of them entrainment of respiratory frequency to the frequency of stimulation occurred at ratios such as 4:3, 4:5, 1:2, 1:3, 1:4, and 1:7. The lowest stimulus intensity required for evoking these phase shifts was between 5 and 10T (threshold of most excitable fibers) for muscle afferents and between 1 and 2T for cutaneous afferents. These results demonstrate the existence of a reflex mechanism capable of locking respiratory frequency to that of a periodic somatic afferent input. They also provide an experimental basis for the hypothesis that reflexes are resposible for the observed locking between step or pedal frequency and respiratory rate during exercise in man.

Animals↗