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At least 829 records · Page 46Linked to original sources
PubMed1997

Oxygen uptake and heart rate responses during arm vs combined arm/electrically stimulated leg exercise in people with paraplegia.

The purpose of this study was to compare the oxygen uptake and heart rate responses during submaximal arm cranking to combined arm cranking + electrical stimulation (ES)-induced leg cycling in individuals with spinal cord injury (SCI). Seven subjects with paraplegia (T4-T12) performed combined arm and leg cycling exercise for 5 min, followed by arm cranking alone at the same power output for a further 5 min. During both exercise conditions, steady state oxygen consumption (VO2), carbon dioxide output (VCO2), expired ventilation (VE) and heart rate (HR) were determined. The respiratory exchange ratio (RER) and oxygen pulse were calculated from the measured variables. During combined arm + electrical stimulation-induced leg cycling exercise, the VO2 was 25% higher (1.58 l min-1 vs 1.26 l min-1), but the HR was 13% lower (132 b min-1 vs 149 b min-1), than during arm cranking exercise alone. Oxygen pulse and VCO2 were also significantly higher (by 42% and 25%, respectively) during combined arm + ES-induced leg exercise, but there were no differences between the two exercise conditions for VE or RER. These data suggest that the absence of the leg 'muscle pump' and a reduced venous return of blood to the heart elevate exercise heart rates during submaximal arm cranking. Conversely, combined arm cranking + ES-induced leg cycling exercise provides the body with a greater metabolic stress than arm cranking alone, while reducing the cardiac stress. The mechanism explaining the heart rate response, however, remains unclear, but may have been influenced by the blood pressure variations across the range of lesions. The findings from this study may have implications for the relative benefit of combined arm + ES-induced leg cycling training for people with paraplegia.

Adult↗
PubMed2000

Plasminogen activation in venous leg ulcers.

BACKGROUND: Venous leg ulceration results from chronic venous insufficiency of the lower extremities. We recently showed that matrix metalloproteinase (MMP) -2 plays a major part in the pathogenesis of venous leg ulcers. In vitro activation of recombinant MMP-2 is controlled by the activity of the urokinase-type plasminogen activator (uPA), which acts as a fibrin-independent plasminogen activator. The activity of MMP-2 is potentiated by binding of uPA to the uPA receptor (uPAR). OBJECTIVES: We aimed to clarify the role of plasminogen activation in venous leg ulcers. METHODS: The expression of uPA, uPAR, the tissue-type plasminogen activator, and plasminogen activator inhibitor (PAI) -1 and PAI-2 was investigated using reverse transcription followed by polymerase chain reaction and Western blotting. RESULTS: These provided direct evidence of elevated expression of uPA and uPAR at the mRNA and protein levels in venous leg ulcers, in comparison with healthy skin. By immunohistochemistry, elevated expression of uPA and uPAR was detected. Fibrin zymography showed significantly elevated endogenous uPA activity in venous leg ulcers in comparison with healthy controls. CONCLUSIONS: Our findings indicate venous leg ulcers to be characterized by elevated plasminogen activation, suggesting that this enzyme cascade plays a crucial part in maintaining proteolytic activity in venous leg ulcers.

Aged↗
PubMed1977

Localization of motor neuron pools supplying identified muscles in normal and supernumerary legs of chick embryo.

Neuromuscular specificity has been investigated in chick embryos with a grafted supernumerary leg. The nerves of the lumbar plexus are divided between the two legs so that rostral nerves innervate the grafted leg and the caudal nerves supply the host's original leg. The basic topographic organization of the histologically definable motor neuron clusters of the lateral motor columns remains unchanged by the addition of a supernumerary leg. Intramuscular injections of identified leg muscles have been used to map the intraspinal location of specific motor pools in stage 38 (12-day) embryos. In the normal embryo, the gastrocnemius muscle is innervated by neurons in a central dorsal cluster of motor neurons in segments 26-29. In six experimental cases, the motor neurons supplying the gastrocnemius muscle of a rostrally placed grafted leg were consistently located in a specific medial cluster of neurons in segments 23-25. Motor neurons in this location never normally innervate a gastrocnemius muscle, even in the very young embryos during the period of naturally occurring cell death. This observation of a systematic mismatch between a particular motor cluster and an abnormally innervated muscle indicates the operation of a selective developmental process. A hierarchy of selective chemoaffinities may best explain our experimental results.

Animals↗
PubMed1987

Influence of single-leg training on muscle metabolism and endurance during exercise with the trained limb and the untrained limb.

We have previously shown that single-leg training results in improved endurance for exercise with the untrained leg (UTL) as well as for exercise with the trained leg (TL). The purpose of this study was to see whether the improved endurance of the untrained leg could be explained on the basis of changes in muscle metabolism. Exercise time to exhaustion at 80% of maximum oxygen uptake (VO2 max) was determined for each leg separately, pre- and post-training. Muscle metabolite concentrations were measured pre- and post-training in biopsy samples obtained immediately before this endurance test and at the pre-training point of exhaustion (END1). After six weeks of single-leg training endurance time was increased for both the UTL and the TL (UTL 34.0 +/- 16.4 min vs 97.9 +/- 26.3 min, P less than 0.01; TL 28.3 +/- 10.1 min vs 169.0 +/- 32.6 min, P less than 0.01). No changes in muscle metabolite concentrations were found in resting muscle. Training increased muscle ATP (P less than 0.05) and glycogen (P less than 0.01) concentrations and decreased muscle lactate concentration (P less than 0.05) in the TL at END1. No significant changes in muscle metabolite concentrations were found for the UTL. The improved endurance of the contralateral limb after single-leg training could not be explained on the basis of changes in muscle metabolism.

Adult↗
PubMed2000

A note on the effects of perches and litter substrate on leg weakness in broiler chickens.

Two trials were conducted to investigate the effect of availability of perches on indices of leg weakness in broiler chickens. A third trial investigated the effect of litter substrate on similar indices of leg weakness in broiler chickens. Leg weakness traits examined were walking ability and tibial dyschondroplasia, tibial curvature, foot burn, and hock burn. Body weight was also measured in all trials. The presence of perches in the rearing pens had no effect on any of the indices of leg weakness examined in either trial. There were no consistent effects of perches on BW. Litter substrate significantly affected some indices of leg weakness; birds reared on wheat straw had poorer walking ability and more foot burn than birds reared on wood shavings, and birds reared on hemp waste were intermediate between them. There was no effect of litter substrate on tibial dyschondroplasia or tibial curvature. Turning the straw litter regularly and adding fresh supplies when necessary did not significantly improve indices of leg weakness. It was concluded that wood shavings provide a better litter substrate than straw, but that perches have no beneficial effect on reducing leg weakness in broilers.

Animals↗
PubMed1994

Evaluation of single-leg standing following anterior cruciate ligament surgery and rehabilitation.

BACKGROUND AND PURPOSE: Although surgical reconstruction of the anterior cruciate ligament (ACL) is commonly performed to increase stability of the knee, persistent changes in neuromuscular function have frequently been cited as contributing to disability. This study investigated single-leg standing balance in a sample of patients 10 to 18 months following reconstructive ACL surgery. In addition, the effect of leg dominance on standing balance was analyzed in a sample of subjects without knee injury. The validity and interrater reliability of a clinical method of measuring balance using observation were also determined. SUBJECTS: Seventy-eight subjects without knee injury and 17 patients following ACL surgery participated in the study after they had been screened for balance disorders. METHODS: Postural sway measurements were recorded during single-leg standing with the subjects' eyes open and closed. Simultaneously, two physical therapists graded each subject's performance using a simple ordinal scale. RESULTS: No differences were found between the dominant and nondominant legs of the subjects without knee injury or between the involved and noninvolved legs of the patients who had undergone ACL surgery. The interrater reliability was high, but limited concurrent validity was found. CONCLUSION AND DISCUSSION: The findings suggest that single-leg standing balance can be reliably evaluated by physical therapists. The single-leg standing balance test, however, may not provide information that assists clinicians in determining clinical change or functional level for patients following rehabilitation for ACL surgery.

Adolescent↗
PubMed2001

Effects of lithotomy position and external compression on lower leg muscle compartment pressure.

BACKGROUND: Case reports have suggested that externally applied pressure from antithrombosis devices may contribute to the development of compartment syndromes during extended surgery in the lithotomy position. The purpose of this study was to assess the effects of a pneumatic compression device on directly measured intracompartment pressure in the lower leg with the leg positioned in the lithotomy position. METHODS: In 25 conscious, healthy men and women, the authors measured pressure within the tibialis anterior muscle compartment with the leg supine and in the lithotomy position with and without intermittent compression. Three different devices were used to keep the leg in the lithotomy position, supporting the leg either behind the knee, under the calf, or at the ankle. RESULTS: The lithotomy position with support behind the calf or knee increased intracompartment pressure to 16.5+/-3.4 versus 10.7+/-5.8 mmHg supine (mean +/- SD; P < 0.05). The addition of intermittent compression decreased pressure to 13.4+/-5.1 mmHg during lithotomy (P < 0.05) and to 9.1+/-7.0 mmHg in the supine position (P < 0.05). In contrast, the lithotomy position with support near the ankle decreased intracompartment pressure to 8.7+/-5.6 versus 13.3+/-5.1 mmHg supine (P < 0.05). The addition of intermittent compression decreased pressure to 6.5+/-5.4 mmHg during lithotomy (P < 0.05) and to 10.3+/-4.7 mmHg in the supine position (P < 0.05). CONCLUSIONS: These results show that the lithotomy position is associated with changes in intracompartment pressure that are dependent on the method of leg support used. Furthermore, they indicate that intermittent external compression can reduce intracompartment pressure in the lower leg. Therefore, increases in intracompartment pressure during surgery in the lithotomy position with the calf or knee supported may be one of the factors that contribute to the development of compartment syndrome. Further, use of intermittent external compression may significantly reduce this pressure increase.

Adult↗
PubMed1995

The straight leg raising test and the severity of symptoms in lumbar disc herniation. A preoperative evaluation.

STUDY DESIGN: In a prospective, consecutive study, correlation between the straight leg raising and other pain-related symptoms in lumbar disc herniation was evaluated preoperatively and postoperatively. OBJECTIVES: All patients were interviewed and examined preoperatively and at follow-up investigations 4 and 12 months postoperatively. SUMMARY OF BACKGROUND DATA: One-hundred-and-fifty consecutive patients underwent lumbar disc surgery. Mean patient age was 42 years (range, 21-81 years). Eighty-nine patients were men and 61 were women. Two herniations occurred at L2-L3, seven at L3-L4, 61 at L4-L5, and 80 at L5-S1. METHODS: Pain at rest, at night, and upon coughing was recorded. Consumption of analgesics was classified into three categories: 1) none, 2) intermittent, or 3) regular. Walking capacity was recorded as > 5 km, 1-5 km, 0.5-1 km, or < 0.5 km. The straight leg raising test was graded pos 0 degree-30 degrees, pos 30 degrees-60 degrees, pos > 60 degrees, or negative. At surgery, the herniation was classified as focal protrusion, subligamentous herniation, or perforation. The patient's assessment of outcome was graded into one of four categories. RESULTS: There was an almost linear correlation between a positive straight leg raising test and pain at rest, pain at night, pain upon coughing, and reduction of walking capacity. Regular consumption of analgesics was more common in patients who had a very restricted positive straight leg raising test (30 degrees). A positive straight leg raising test early postoperatively correlated with inferior outcome of the surgical procedure. CONCLUSION: The straight leg raising test as performed in clinical practice has a strong correlation with various parameters that signify the pain level of the patient. A positive straight leg raising test postoperatively correlates with inferior surgical outcome.

Adult↗
PubMed2001

Precise tuning of barnacle leg length to coastal wave action.

Both spatial and temporal variation in environmental conditions can favour intraspecific plasticity in animal form. But how precise is such environmental modulation? Individual Balanus glandula Darwin, a common northeastern Pacific barnacle, produce longer feeding legs in still water than in moving water. We report here that, on the west coast of Vancouver Island, Canada, the magnitude and the precision of this phenotypic variation is impressive. First, the feeding legs of barnacles from protected bays were nearly twice as long (for the same body mass) as those from open ocean shores. Second, leg length varied surprisingly precisely with wave exposure: the average maximum velocities of breaking waves recorded in situ explained 95.6-99.5% of the variation in average leg length observed over a threefold range of wave exposure. The decline in leg length with increasing wave action was less than predicted due to simple scaling, perhaps due to changes in leg shape or material properties. Nonetheless, the precision of this relationship reveals a remarkably close coupling between growth environment and adult form, and suggests that between-population differences in barnacle leg length may be used for estimating differences in average wave exposure easily and accurately in studies of coastal ecology.

Adaptation, Physiological↗
PubMed2005

Improved healing rates for chronic venous leg ulcers: pilot study results from a randomized controlled trial of a community nursing intervention.

Venous leg ulcers are a frequent source of chronic ill-health and a considerable cost to health-care systems. This paper reports pilot study results from a randomized controlled trial to determine the effectiveness of a community-based 'Leg Club' environment on improving healing rates of venous leg ulcers. Leg Clubs offer a setting where people with similar problems can socialize in a supportive, information-sharing environment. A sample of 33 clients with a below-knee venous leg ulcer were randomized to treatment, either in their own homes or in a community Leg Club. Treatment was provided to all participants, whether in the control group or intervention group, by a team of trained wound-care nurses following evidence-based assessment and treatment guidelines. Data were collected on admission to the study and at 12 weeks from admission. Results showed a significant improvement in healing in the intervention group compared to the control group, as measured by ulcer area size and Pressure Ulcer Scale for Healing scores. These results suggest that a community Leg Club environment provides benefits additional to wound care expertise and evidence-based care. Knowledge gained from this study provides evidence to guide service delivery and improve client outcomes.

Activities of Daily Living↗
PubMed2005

Modulation of membrane potential in mesothoracic moto- and interneurons during stick insect front-leg walking.

During walking, maintenance and coordination of activity in leg motoneurons requires intersegmental signal transfer. In a semi-intact preparation of the stick insect, we studied membrane potential modulations in mesothoracic (middle leg) motoneurons and local premotor nonspiking interneurons that were induced by stepping of a front leg on a treadmill. The activity in motoneurons ipsi- and contralateral to the stepping front leg was recorded from neuropilar processes. Motoneurons usually exhibited a tonic depolarization of < or =5 mV throughout stepping sequences. This tonic depolarization depended on membrane potential and was found to reverse in the range of -32 to -47 mV. It was accompanied by a mean membrane resistance decrease of approximately 12%. During front-leg stepping, an increased spike activity to depolarizing current pulses was observed in 73% of contralateral flexor motoneurons that were tested. Motoneurons ipsilateral to the walking front leg exhibited phasic membrane potential modulations coupled to steps in accordance with previously published results. Coupling patterns were typical for a given motoneuron pool. Local nonspiking mesothoracic interneurons that provide synaptic drive to tibial motoneurons also contribute to the modulation of membrane potential of tibial motoneurons during front-leg walking. We hypothesize that the tonic depolarization of motoneurons during walking is a cellular correlate of arousal that usually increases effectiveness of phasic excitation in supporting motoneuron firing.

Animals↗
PubMed1995

Nonspiking local interneurons in insect leg motor control. I. Common layout and species-specific response properties of femur-tibia joint control pathways in stick insect and locust.

1. Locusts (Locusta migratoria) and stick insects (Carausius morosus) exhibit different strategies for predator avoidance. Locusts rely primarily on walking and jumping to evade predators, whereas stick insects become cataleptic, catalepsy forming a major component of the twig mimesis exhibited by this species. The neuronal networks that control postural leg movements in locusts and stick insects are tuned differently to their specific behavioral tasks. An important prerequisite for the production of catalepsy in the stick insect is the marked velocity dependency of the control network, which appears to be generated at the level of nonspiking local interneurons. We examined interneuronal pathways in the network controlling the femur-tibia joint of the locust middle leg and compared its properties with those described for the stick insect middle leg. It was our aim to identify possible neural correlates of the species-specific behavior with regard to postural leg motor control. 2. We obtained evidence that the neuronal networks that control the femur-tibia joints in the two species consist of morphologically and physiologically similar--and thus probably homologous--interneurons. Qualitatively, these interneurons receive the same input from the femoral chordotonal organ receptors and they drive the same pools of leg motoneurons in both species. 3. Pathways that contribute to the control of the femur-tibia joint include interneurons that support both "resisting" and "assisting" responses with respect to the motoneuron activity that is actually elicited during reflex movements. Signal processing via parallel, antagonistic pathways therefore appears to be a common principle in insect leg motor control. 4. Differences between the two insect species were found with regard to the processing of velocity information provided by the femoral chordotonal organ. Interneuronal pathways are sensitive to stimulus velocity in both species. However, in the locust there is no marked velocity dependency of the interneuronal responses, whereas in the same interneurons of the stick insect it is pronounced. This characteristic was maintained at the level of the motoneurons controlling the femur-tibia joint. Pathways for postural leg motor control in the locust thus lack an important prerequisite for the generation of catalepsy, that is, a marked velocity dependency.

Animals↗
PubMed2006

Anterior-posterior ground reaction forces as a measure of paretic leg contribution in hemiparetic walking.

BACKGROUND AND PURPOSE: Walking after stroke is characterized by slow gait speed, poor endurance, reduced quality and adaptability of walking patterns, and an inability to coordinate the legs. Estimates based on mechanical work calculations have suggested that the paretic leg does 30% to 40% of the total mechanical work over the gait cycle, regardless of hemiparetic severity, but these work estimates may not describe the contribution of each leg to forward propulsion. The purpose of this study was to establish a quantifiable link between hemiparetic severity and paretic leg contribution to propulsion during walking, which we propose to quantify using a measure based on the anterior-posterior ground reaction forces (A-P GRFs). METHODS: A total of 47 participants with chronic hemiparesis walked at self-selected speeds to collect spatiotemporal parameters and 3D GRFs. A 16-person subset also participated in a pedaling protocol to compare A-P GRF measures to established measures of paretic leg output. RESULTS: A-P GRF measures were correlated with both walking speed and hemiparetic severity. These measures were also strongly correlated with positive work and net work values obtained during the pedaling task. The percentage of total propulsion generated by the paretic leg (PP) was calculated and found to be 16%, 36%, and 49% for those with high, moderate, and low hemiparetic severity, respectively. CONCLUSIONS: PP was found to provide a quantitative measure of the coordinated output of the paretic leg. Further research on this measure of forward propulsion may lead to the provision of an effective tool for distinguishing functional compensation from physiological restitution.

Aged↗
PubMed1996

Locomotory behavior in the hawkmoth Manduca sexta: kinematic and electromyographic analyses of the thoracic legs in larvae and adults.

During metamorphosis in Manduca sexta, muscles and most sensory structures of the thoracic legs undergo extensive changes while the motor neurons that are present in the larva persist into the adult. The main goal of this work was to identify similarities and dissimilarities in thoracic leg movements during crawling in larvae and walking in adults. This information provides a foundation for understanding the extent to which centrally located neural elements are reorganized during metamorphosis to accommodate changes in locomotion. Analysis of electromyographic activity from leg muscles synchronized with video-taped recordings of the leg movements during larval crawling and adult walking revealed differences in cycle periods as well as intersegmental and intrasegmental patterns of coordination. Larval crawling was characterized by synchronous movements of segmental pairs of legs as activity proceeded slowly from the move posterior to the more anterior segments. During crawling, antagonistic muscles maintained a strict reciprocity. In contrast, walking in adults was characterized by fast, alternating movements of the left and right prothoracic legs and more variable coordination patterns in the mesothoracic and metathoracic legs (ranging from synchrony to alternation). In adults, sensory information, possibly associated with the weight-bearing or postural demands of walking on an incline, contributed to a strong dependence between the duration of muscle activity and cycle period and to the extent that the muscle activity overlapped during walking.

Animals↗
PubMed1997

Variability of leg kinematics in free-walking crayfish, Procambarus clarkii, and related inter-joint coordination

The inter-joint coordination in leg 4 of the crayfish Procambarus clarkii was investigated while they travelled freely along straight paths. Video analysis of the kinematics of the leg's three-dimensional motion, combined with a statistical method based on conjugate cross-correlation functions, showed stable inter-joint coordination in the leg kinematics. In particular, the inter-joint coordination involved a strong movement in the distal mero-carpopodite (M-C) joint occurring between the movements of the proximal thoraco-coxopodite and coxo-basal joints; thus, the leg extended during the swing phase and flexed during the stance phase. This synchronisation was mainly independent of global changes in the locomotor pattern induced by variation in speed or contralateral inter-leg coupling which occurred during free walking. The main changes in inter-joint coordination were found to be related to the appearance of a biphasic flexion/extension movement during each stroke of the step cycle when the leg retracted far backwards. This movement was observed more frequently in large animals and was therefore possibly related to changes in postural control. The functional role of this distal M-C joint movement in the leg motion is discussed.

Journal Article↗
PubMed1975

Motor innervation within supernumerary legs of cockroaches.

1. Clusters of legs having prothoracic and metathoracic origins were grown from the metathoracic coxa of the cockroach. 2. Or occasionally two, of the three major nerves innervating the cockroach leg. 3. Stimulation of a particular leg nerve (no. 3, 5 or 6) evoked movement at the same joints and in the same directions in a leg having only one nerve as in a normal leg. 4. Stimulation of a particular metathoracic nerve generally produced the same movements in a prothoracic leg transplanted to the metathoracic site as it did in a regenerated or intact metathoracic leg.

Action Potentials↗
PubMed2003

Pain in pure and mixed aetiology venous leg ulcers: a three-phase point prevalence study.

OBJECTIVE: This study aimed to determine the point prevalence of venous leg ulcer pain over three seasons (autumn, winter and spring). It also collated profiles of individuals with venous ulceration and described the characteristics of people with and without venous leg ulcer pain. METHOD: The study sample comprised 255 people with pure and mixed venous leg ulcers who were receiving care in a Canadian community leg ulcer service. Prevalence was determined by the number of individuals who had experienced pain in the past 24 hours. The profile of individuals was developed by analysing sociodemographic, circumstance-of-living, clinical and health-related quality-of-life data collected on admission to the leg ulcer service. RESULTS: Over the three prevalence periods, the prevalence of pain for the total sample ranged from 48% to 54%. Prevalences at each of the study periods for individuals who had been receiving care for less than 13 weeks, and for the first measure of pain only, were almost identical, ranging from 48-59%. The mean pain-severity score was less than three (out of 10) in all three periods. Of the individuals with pain, 50% or more used analgesia and, of these, over 75% reported it was effective. The profile of participants with pain was similar to those without it, except that the former were significantly more likely to have osteoarthritis, a foot ulcer, to have been attending the leg service for a shorter time period and to have a lower SF-12 mental health component score. CONCLUSION: These results demonstrate that leg ulcer management must include pain assessment and consideration of the factors that may be associated with pain. A large prospective repeated measures study is needed to increase understanding of the extent of pain, the use and efficacy of analgesia, and the factors that may be related to experiencing pain.

Aged↗
PubMed2003

Effect of pre-exhaustion exercise on lower-extremity muscle activation during a leg press exercise.

The purpose of this study was to investigate the effect of pre-exhaustion exercise on lower-extremity muscle activation during a leg press exercise. Pre-exhaustion exercise, a technique frequently used by weight trainers, involves combining a single-joint exercise immediately followed by a related multijoint exercise (e.g., a knee extension exercise followed by a leg press exercise). Seventeen healthy male subjects performed 1 set of a leg press exercise with and without pre-exhaustion exercise, which consisted of 1 set of a knee extension exercise. Both exercises were performed at a load of 10 repetitions maximum (10 RM). Electromyography (EMG) was recorded from the rectus femoris, vastus lateralis, and gluteus maximus muscles simultaneously during the leg press exercise. The number of repetitions of the leg press exercise performed by subjects with and without pre-exhaustion exercise was also documented. The activation of the rectus femoris and the vastus lateralis muscles during the leg press exercise was significantly less when subjects were pre-exhausted (p < 0.05). No significant EMG change was observed for the gluteus maximus muscle. When in a pre-exhausted state, subjects performed significantly (p < 0.001) less repetitions of the leg press exercise. Our findings do not support the popular belief of weight trainers that performing pre-exhaustion exercise is more effective in order to enhance muscle activity compared with regular weight training. Conversely, pre-exhaustion exercise may have disadvantageous effects on performance, such as decreased muscle activity and reduction in strength, during multijoint exercise.

Adult↗