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PubMed2006

Compliant leg behaviour explains basic dynamics of walking and running.

The basic mechanics of human locomotion are associated with vaulting over stiff legs in walking and rebounding on compliant legs in running. However, while rebounding legs well explain the stance dynamics of running, stiff legs cannot reproduce that of walking. With a simple bipedal spring-mass model, we show that not stiff but compliant legs are essential to obtain the basic walking mechanics; incorporating the double support as an essential part of the walking motion, the model reproduces the characteristic stance dynamics that result in the observed small vertical oscillation of the body and the observed out-of-phase changes in forward kinetic and gravitational potential energies. Exploring the parameter space of this model, we further show that it not only combines the basic dynamics of walking and running in one mechanical system, but also reveals these gaits to be just two out of the many solutions to legged locomotion offered by compliant leg behaviour and accessed by energy or speed.

Biomechanical Phenomena↗
PubMed2004

Medical conditions associated with venous leg ulcers.

BACKGROUND: In patients who have a venous leg ulcer, very little is known about the frequency of their concomitant medical conditions. OBJECTIVES: To evaluate the frequency that other medical conditions are associated with a new venous leg ulcer. METHODS: We studied a 10% random sample of elderly patients registered in the General Practice Research Database between 1988 and 1996. We describe the frequency of medical conditions using simple percentages. In order to assess the associations between medical conditions and the onset of a venous leg ulcer, we used logistic regression models. RESULTS: Several medical conditions occur commonly in patients who develop venous leg ulcers, including anaemia, angina, asthma, cellulitis of the lower extremity, depression, diabetes, limb oedema, hypertension, osteoarthritis, pneumonia and urinary tract infection. After statistical adjustment many medical conditions were significantly associated with those who had recent onset of a venous leg ulcer, including asthma, cellulitis of the lower extremity, congestive heart failure, diabetes, deep venous thrombosis, lower limb oedema, osteoarthritis, peripheral vascular arterial disease of the lower extremity, rheumatoid arthritis, history of hip surgery, and history of venous surgery/ligation. Unexpectedly, some illnesses were inversely associated with those that had recent onset of a venous leg ulcer, including angina, cerebral vascular accident, depression, malignancy, myocardial infarction, pneumonia and urinary tract infection. CONCLUSIONS: Physicians caring for individuals with venous leg ulcers need to be aware that it is likely that these individuals may have one of the comorbid illnesses listed above.

Aged↗
PubMed2006

Sociodemographic factors in chronic leg ulceration.

BACKGROUND: While there is a commonly held belief that leg ulceration is associated with social factors, the evidence to support this is mainly anecdotal. OBJECTIVES: To determine deficits in sociodemographic status in patients with chronic leg ulceration. In a matched case-control study carried out in community leg ulcer clinics and participants' homes within Wandsworth Primary Care Trust, patients with chronic leg ulceration were compared with age- and sex-matched community controls drawn from general practitioner registers. Main outcome measures were the prevalence of social class, ethnicity, marital status, living status and social support. Data were analysed by conditional logistic regression. RESULTS: In all, 113 patients were identified and matched to controls. Patients had a mean age of 75 years (range 31-94), with 72 (64%) being women. The ulcer had been present for a median of 8 months (range 0.8-144), and 29% of patients had an area of ulceration >10 cm(2) (range 0.5-171.5). Being Afro-Caribbean increased the risk of leg ulceration eightfold (95% confidence interval, CI 1.83-34.75; P < 0.001) compared with the white population. There was a gradient with social class, with patients with leg ulcers being more likely to come from social class IV and V (odds ratio, OR 2.82, 95% CI 1.19-6.74; P = 0.015). Never having married (OR 2.98, 95% CI 1.15-7.74; P = 0.025), living in rented housing (P < 0.001) and having a mobility deficit (P < 0.001) more often occurred in the ulcer patients, while living with a spouse was protective (OR 0.46, 95% CI 0.21-0.99; P = 0.048). Patients with ulceration experienced significantly poorer social support than their controls for most subscales of the medical outcomes study social support questionnaire (all P < 0.05). CONCLUSIONS: Chronic leg ulceration is associated with poorer socioeconomic status, and factors which relate to social isolation. At present it is not possible to determine whether these associations are causative or are a consequence of the ulceration.

Adult↗
PubMed1991

Insulin time-dependent effects on the leg exchange of glucose and amino acids in man.

Time-dependent effects of insulin on the leg exchange of glucose, lactate, glycerol, free fatty acids (FFA) and amino acids were measured in relation to oxygen uptake (leg and whole body) and whole body glucose assimilation including oxidation. Seven healthy males (58 +/- 3 years of age) were investigated before operation of uncomplicated inguinal hernia or varicose veins. Euglycaemic glucose clamp investigations with systemic hyperinsulinaemia between 100-120 mU1(-1) were used. Metabolic measurements were performed before and during hyperinsulinaemia at 2 and 6 h following the start of glucose clamp to evaluate the time-dependency of insulin actions. Whole body glucose uptake increased continuously for up to 6 h (from 4.7 +/- 0.7 to 8.0 +/- 0.8 mg/kg/min, P less than 0.01) despite stable plasma concentrations of glucose and insulin. This was also true for glucose oxidation. Whole body oxygen uptake did not change significantly during the clamp while the leg exchange of oxygen uptake did (from 5.9 +/- 0.86 mumol/100 g/min to 11.6 +/- 2.4, P less than 0.01). Insulin effect on leg blood flow was time-dependent and increased two-fold (2.3 +/- 0.4 ml/100 g/min to 4.4 +/- 0.9, P less than 0.001) during clamp. The leg production of lactate increased continuously, accounting for approximately 15% of the glucose uptake across the leg, but the rise in arterial lactate did not reach the level of statistical significance. Plasma FFA concentrations decreased in a time-dependent manner during clamp, while the leg exchange of FFA switched rapidly to a stable net uptake.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗
PubMed2005

Favourable association of leg fat with cardiovascular risk factors.

OBJECTIVES: To assess the association of trunk and leg fat mass (FM) and leg lean tissue mass (LTM) with conventional cardiovascular risk factors. DESIGN: Cross-sectional study. SETTING AND SUBJECTS: We studied 1249 men and 3007 women (age 20-79 years) who attended a research institute for a health checkup between October 1995 and February 2004. MAIN OUTCOME MEASURES: Body mass index, waist circumference (WC), hip circumference (HC), systolic and diastolic blood pressure, total cholesterol, HDL cholesterol, triglycerides, glucose and haemoglobin A(1C) were measured. Trunk FM, leg FM and leg LTM were obtained by dual-energy X-ray absorptiometry. We evaluated the associations between the indices for regional body composition and cardiovascular risk factors, which included hypertension, hypercholesterolaemia, hypo-HDL cholesterolaemia, hypertriglyceridaemia, dyslipidaemia and diabetes mellitus. RESULTS: Increase in WC and HC respectively showed increase and decrease in odds ratios of cardiovascular risk factors. Increase in trunk FM by 1 kg significantly increased the risk of the cardiovascular risk factors with the odds ratios ranging between 1.11 and 1.45. Increase in leg FM by 1 kg significantly decreased the risk with the odds ratios ranging between 0.52 and 0.90, except for the nonsignificant results for hypercholesterolaemia and hypo-HDL cholesterolaemia in men. Odds ratios of 1 kg increase in leg LTM were only significant for dyslipidaemia in men and hypercholesterolaemia in women (both 0.93). CONCLUSIONS: WC and HC showed opposite and independent associations with cardiovascular risk factors. The favourable association of HC was mainly attributable to that of leg FM.

Adipose Tissue↗
PubMed1996

Optimizing the hospital management of leg ulcers.

BACKGROUND: Leg ulcers are common and are often the cause of a long hospital admission. However, little information is available on the efficacy and efficiency of inpatient leg ulcer management. The inpatient management of leg ulceration was examined and areas for improvement were sought. METHODS: The management of patients admitted to a teaching hospital with a primary diagnosis of leg ulceration was examined, the costs estimated and areas for improvement identified. A retrospective analysis of 174 admissions to Heidelberg Repatriation Hospital between 1 January 1991 and 31 December 1992 was performed. RESULTS: Of 119 patients, 61 had ulcers due to arterial disease and 34 due to venous disease. Over 2 years, leg ulcers accounted for 5259 inpatient bed days, a mean of 44.2 days per patient. The estimated cost exceeded $2,750,000, averaging over $12,000 per admission. Thirty-three percent of patients had no recorded investigations into the cause of their ulcer and fewer than 50% had documented improvement at discharge. CONCLUSIONS: Leg ulcers are costly due to their extended treatment on an inpatient basis. Unfortunately, hospital admission does not guarantee optimal wound healing rates. A leg ulcer protocol is proposed to minimize inpatient stay and improve investigation and management in an outpatient or community setting.

Aged↗
PubMed1999

Cardiovascular control during concomitant dynamic leg exercise and static arm exercise in humans.

1. Skeletal muscle blood flow is thought to be determined by a balance between sympathetic vasoconstriction and metabolic vasodilatation. The purpose of this study was to assess the importance of high levels of sympathetic vasoconstrictor activity in control of blood flow to human skeletal muscle during dynamic exercise. 2. Muscle sympathetic nerve activity to the exercising leg was increased by static or static ischaemic arm exercise added to on-going dynamic leg exercise. Ten subjects performed light (20 W) or moderate (40 W) dynamic knee extension for 6 min with one leg alone or concomitant with bilateral static handgrip at 20% of maximal voluntary contraction force with or without forearm muscle ischaemia or post-exercise forearm muscle ischaemia. 3. Muscle sympathetic nerve activity was measured by microneurography (peroneal nerve) and leg muscle blood flow by a constant infusion thermodilution technique (femoral vein). 4. Activation of an exercise pressor reflex from the arms, causing a 2- to 4-fold increase in muscle sympathetic nerve activity and a 15-32% increase in mean arterial blood pressure, did not affect blood flow to the dynamically exercising leg muscles at any level of leg exercise. Leg vascular conductance was reduced in line with the higher perfusion pressure. 5. The results demonstrate that the vasoconstrictor effects of high levels of muscle sympathetic nerve activity does not affect blood flow to human skeletal muscle exercising at moderate intensities. One question remaining is whether the observed decrease in muscle vascular conductance is the result of sympathetic vasoconstriction or metabolic autoregulation of muscle blood flow.

Adult↗
PubMed1989

Role of leg vasculature in the cardiovascular response to arm work in wheelchair-dependent populations.

To assess the effects of leg vasculature on cardiovascular dynamics during submaximal arm work, oxygen uptake (VO2), cardiac output (Q) and heart rate (HR) were measured during arm-crank ergometry (ACE) at 35 W (45% peak ACE VO2) in five able-bodied subjects, five wheelchair-dependent paraplegics, and five wheelchair-dependent bilateral amputees who represented the conditions of active, passive, and absence of leg musculature respectively. Arteriovenous oxygen difference (a-v O2) and stroke volume (SV) were calculated from VO2, Q and HR. An index of leg fluid accumulation and leg blood flow was measured in the paraplegics and able-bodied subjects during rest and ACE. VO2, Q, and a-v O2 during ACE were not statistically different among the three groups. However, paraplegics exhibited higher HR (P less than 0.05) and lower SV (P less than 0.06) during exercise compared to both amputees and able-bodied subjects. Greater (P less than 0.05) leg fluid accumulation was measured in paraplegics compared to able-bodied subjects, although no statistically significant differences in leg blood flow were observed. Although our results are limited to a small number of subjects, these data suggest that an active muscle pump contributes significantly to elevated venous return and stroke volume during ACE. The legs of the paraplegic appear to act as a reservoir for fluid accumulation which may limit cardiac filling, particularly during moderate arm work to support wheelchair function.

Adult↗
PubMedDate not supplied

Klinefelter's syndrome presenting with leg ulcers.

A 54-year-old man of Persian origin presented to our department with a 1-year history of ulcers on the right leg that had been unresponsive to numerous topical treatments, accompanied by lymphedema of the right leg. Medical history included hypergonadotropic hypogonadism, which had not been further investigated. He was treated for 20 years with testosterone IM once monthly, which he stopped a year before the current hospitalization for unclear reasons. The patient reported no congenital lymphedema. Physical examination revealed two deep skin ulcers (Figure 1) on the right leg measuring 10 cm in diameter with raised irregular inflammatory borders and a boggy, necrotic base discharging a purulent hemorrhagic exudate. Bilateral leg pitting edema and right lymphangitis with lymphadenitis were noted. He had low head hair implantment, sparse hair on the body and head, hyperpigmentation on both legs, onychodystrophia of the toenails (mainly the large toe and less prominent on the other toes), which was atrophic lichen-planus-like in appearance and needed no trimming (Figure 2), normal hand nails, oral thrush, and angular cheilitis. Other physical findings were gynecomastia, pectus excavatum, small and firm testicles, long extremities, asymmetrical goiter, systolic murmur 2/6 in left sternal border, and slow and inappropriate behavior. The patient's temperature on admission was 39 degrees C. Blood cultures were negative for bacterial growth. Results of laboratory investigations included hemoglobin (11.2 g/dL), hematocrit (26.8%), normal mean corpuscular volume and mean corpuscular hemoglobin volume, and red blood cell distribution width (16%). Blood smear showed spherocytes, slight hypochromia, anisocytosis, macrocytosis, and microcytosis. Blood chemistry values were taken for iron (4 micro g/dL [normal range 40-150 micro g/dL]), transferrin (193 mg/dL [normal range 220-400 mg/dL]), ferritin (1128 ng/mL [normal range 14-160 ng/mL]), transferrin saturation (1.5% [normal range 20%-55%]), serum folate (within normal limits), and vitamin B12 (within normal limits). Direct Coombs' test equaled positive 2 + IgG. All these values indicated anemia of chronic diseases combined with hemolytic anemia. Further blood work-up tested antinuclear antibody (positive <1:80 homogeneous pattern), rheumatoid factors (143 IU/mL [positive >8.5 IU/mL]), C-reactive protein (286 mg/L [normal range 0-5 mg/L]), anticardiolipin IgM antibody (9.0 monophosphoryl lipid U/mL [normal range 0-7.00 MPL U/mL]) and antithrombin III activity (135% [normal range 74%-114%]). Results of other blood tests were within normal limits or negative, including lupus anticoagulant, beta2 glycoprotein, anticardiolipin IgG Ab, anti-ss DNA Ab, C3, C4, anti-RO, anti-LA, anti-SC-70, anti-SM Ab, P-ANCA, C-ANCA, TSH, FT4, anti-T microsomal, antithyroglobulin, protein C activity, protein S free, cryoglobulins, serum immunoelectrophoresis, VDRL, hepatitis C antibodies, hepatitis B antigen, and human immunodeficiency virus. Endocrinological work-up examined luteinizing hormone (22.9 mIU/mL [normal range for adult men 0.8-6 mIU/mL]), follicle stimulating hormone (49.7 mIU/mL [normal range for adult men 1-11 mIU/mL]), testosterone (0.24 ng/mL [normal range for adult men 2.5-8.0 ng/mL]), bioavailable testosterone (0.02 ng/mL [normal range for adult men >0.6 ng/mL]), and percent bioavailable test (8.1% [normal value >20%]). These results indicate hypergonadotropic hypogonadism. Plasminogen activator inhibitor 1 was 6 U (normal value 5-20 U/mL). Karyotyping performed by G-banding technique revealed a 47 XXY karyotype, which is diagnostic of Klinefelter's syndrome. Doppler ultrasound of the leg ulcers disclosed partial thrombus in the distal right femoral vein. X-rays and bone scan displayed osteomyelitis along the right tibia. Histological examination of a 4-mm punch biopsy from the ulcer border revealed hyperkeratosis, acanthosis, hypergranulosis, and mixed inflammatory infiltrate containing eosinophils compatible with chronic ulcer. Multiple vessels were seen, compatible with a healing process. Direct immunofluorescence of the biopsy revealed granular IgM in the dermo-epidermal junction. Indirect immunofluorescence was negative. Thyroid function tests showed normal thyroid stimulating hormone and free throxine4. Multinodular goiter was seen on thyroid scan and ultrasound. Thyroid fine needle aspiration was compatible with multinodular goiter (normal follicular cells, free colloid, macrophages with pigment). IV treatment with amoxicillin-clavulanic acid 1 g t.i.d. was administered for 2 weeks, with a decrease in temperature and normalization of the leukocyte level. Oral antibiotic treatment with amoxicillin-clavulanic acid was continued for 10 more days, followed by 25 days of ciprofloxacin for the osteomyelitis. Local treatment included saline soakings followed by application of Promogran (Johnson & Johnson, New Brunswick, NJ) and Kaltostat (ConvaTec Ltd., a Bristol-Myers Squibb Company, New York, NY) with slight improvement. At the same time, the patient was treated with warfarin sodium due to deep vein thrombosis under international normalized ratio 2-3. The patient was treated with IM testosterone once monthly for 1 year, which resulted in a reduction in the diameter and depth of the leg ulcers (Figure 3). Blood tests were not performed for follow-up of the immune state.

Humans↗
PubMed1993

Restless legs syndrome in the elderly.

The prevalence and significance of restless legs syndrome was assessed in 307 patients presenting to an acute-care geriatric medical service. Fifteen patients (5%) had restless legs syndrome; 13 (87%) of these patients had insomnia and 10 (67%) reported troublesome or frequent leg symptoms. Of 147 patients with current insomnia, iron deficiency (serum ferritin < 18 ng/ml) was present in 4/13 (31%) patients with restless legs and 8/134 (6%) patients without restless legs (P < 0.025). Improvement in symptoms of restless legs was noted with iron repletion. These findings suggest that restless legs syndrome is relatively common in the elderly and causes significant discomfort and sleep disturbance. Iron deficiency is a common and treatable cause.

Aged↗
PubMed2006

Derangements in mitochondrial metabolism in intercostal and leg muscle of critically ill patients with sepsis-induced multiple organ failure.

Critically ill patients treated for multiple organ failure often develop muscle dysfunction. Here we test the hypothesis that mitochondrial and energy metabolism are deranged in leg and intercostal muscle of critically ill patients with sepsis-induced multiple organ failure. Ten critically ill patients suffering from sepsis-induced multiple organ failure and requiring mechanical ventilation were included in the study. A group (n = 10) of metabolically healthy age- and sex-matched patients undergoing elective surgery were used as controls. Muscle biopsies were obtained from the vastus lateralis (leg) and intercostal muscle. The activities of citrate synthase and mitochondrial respiratory chain complexes I and IV and concentrations of ATP, creatine phosphate, and lactate were analyzed. Morphological evaluation of mitochondria was performed by electron microscopy. Activities of citrate synthase and complex I were 53 and 60% lower, respectively, in intercostal muscle of the patients but not in leg muscle compared with controls. The activity of complex IV was 30% lower in leg muscle but not in intercostal muscle. Concentrations of ATP and creatine phosphate were, respectively, 40 and 34% lower, and lactate concentrations were 43% higher in leg muscle but not in intercostal muscle. We conclude that both leg and intercostal muscle show a twofold decrease in mitochondrial content in intensive care unit patients with multiple organ failure, which is associated with lower concentrations of energy-rich phosphates and an increased anaerobic energy production in leg muscle but not in intercostal muscle.

Adenosine Triphosphate↗
PubMed1977

Comparison of arm versus leg work in induction of acute episodes of asthma.

The severity of exercise-induced asthma varies with the type of exercise performed. To determine whether such variation could be attributed to the use of different muscle groups, we exercised arms separately from legs using a bicycle ergometer. First, arms were exercised to exhaustion, then legs were exercised at the same load for the same duration. Arm work resulted in greater ventilation, heart rate, hydrogen ion concentration, and airway obstruction than did leg work. Later, legs were exercised to exhaustion using a load more than twice that of the arm work. Both the exhausting leg work and exhausting arm work resulted in significant bronchospasm and acidosis, whereas the nonexhausting leg work did not. These data suggest that, in arm and/or leg exercise, the relationship of work load to muscle mass is a determinant of airway obstruction.

Adult↗
PubMed1998

Mechanism of leg stiffness adjustment for hopping on surfaces of different stiffnesses.

When humans hop in place or run forward, leg stiffness is increased to offset reductions in surface stiffness, allowing the global kinematics and mechanics to remain the same on all surfaces. The purpose of the present study was to determine the mechanism for adjusting leg stiffness. Seven subjects hopped in place on surfaces of different stiffnesses (23-35,000 kN/m) while force platform, kinematic, and electromyographic data were collected. Leg stiffness approximately doubled between the most stiff surface and the least stiff surface. Over the same range of surfaces, ankle torsional stiffness increased 1.75-fold, and the knee became more extended at the time of touchdown (2.81 vs. 2.65 rad). We used a computer simulation to examine the sensitivity of leg stiffness to the observed changes in ankle stiffness and touchdown knee angle. Our model consisted of four segments (foot, shank, thigh, head-arms-trunk) interconnected by three torsional springs (ankle, knee, hip). In the model, an increase in ankle stiffness 1.75-fold caused leg stiffness to increase 1.7-fold. A change in touchdown knee angle as observed in the subjects caused leg stiffness to increase 1.3-fold. Thus both joint stiffness and limb geometry adjustments are important in adjusting leg stiffness to allow similar hopping on different surfaces.

Adult↗
PubMed2006

Left ventricular function during arm exercise: influence of leg cycling and lower body positive pressure.

The purpose of this study was to characterize left ventricular (LV) diastolic filling and systolic performance during graded arm exercise and to examine the effects of lower body positive pressure (LBPP) or concomitant leg exercise as means to enhance LV preload in aerobically trained individuals. Subjects were eight men with a mean age (+/-SE) of 26.8 +/- 1.2 yr. Peak exercise testing was first performed for both legs [maximal oxygen uptake (Vo(2)) = 4.21 +/- 0.19 l/min] and arms (2.56 +/- 0.16 l/min). On a separate occasion, LV filling and ejection parameters were acquired using non-imaging scintography using in vivo red blood cell labeling with technetium 99(m) first during leg exercise performed in succession for 2 min at increasing grades to peak effort. Graded arm exercise (at 30, 60, 80, and 100% peak Vo(2)) was performed during three randomly assigned conditions: control (no intervention), with concurrent leg cycling (at a constant 15% leg maximal Vo(2)) or with 60 mmHg of LBPP using an Anti G suit. Peak leg exercise LV ejection fraction was higher than arm exercise (60.9 +/- 1.7% vs. 55.9 +/- 2.7%; P < 0.05) as was peak LV end-diastolic volume was reported as % of resting value (110.3 +/- 4.4% vs. 97 +/- 3.7%; P < 0.05) and peak filling rate (end-diastolic volume/s; 6.4 +/- 0.28% vs. 5.2 +/- 0.25%). Concomitant use of either low-intensity leg exercise or LBPP during arm exercise failed to significantly increase LV filling or ejection parameters. These observations suggest that perturbations in preload fail to overcome the inherent hemodynamic conditions present during arm exercise that attenuate LV performance.

Adult↗
PubMed2002

Increased vascular resistance in paralyzed legs after spinal cord injury is reversible by training.

The purpose of the present study was to determine the effect of a spinal cord injury (SCI) on resting vascular resistance in paralyzed legs in humans. To accomplish this goal, we measured blood pressure and resting flow above and below the lesion (by using venous occlusion plethysmography) in 11 patients with SCI and in 10 healthy controls (C). Relative vascular resistance was calculated as mean arterial pressure in millimeters of mercury divided by the arterial blood flow in milliliters per minute per 100 milliliters of tissue. Arterial blood flow in the sympathetically deprived and paralyzed legs of SCI was significantly lower than leg blood flow in C. Because mean arterial pressure showed no differences between both groups, leg vascular resistance in SCI was significantly higher than in C. Within the SCI group, arterial blood flow was significantly higher and vascular resistance significantly lower in the arms than in the legs. To distinguish between the effect of loss of central neural control vs. deconditioning, a group of nine SCI patients was trained for 6 wk and showed a 30% increase in leg blood flow with unchanged blood pressure levels, indicating a marked reduction in vascular resistance. In conclusion, vascular resistance is increased in the paralyzed legs of individuals with SCI and is reversible by training.

Adult↗
PubMed2005

Energy cost and muscular activity required for leg swing during walking.

To investigate the metabolic cost and muscular actions required for the initiation and propagation of leg swing, we applied a novel combination of external forces to subjects walking on a treadmill. We applied a forward pulling force at each foot to assist leg swing, a constant forward pulling force at the waist to provide center of mass propulsion, and a combination of these foot and waist forces to evaluate leg swing. When the metabolic cost and muscle actions were at a minimum, the condition was considered optimal. We reasoned that the difference in energy consumption between the optimal combined waist and foot force trial and the optimal waist force-only trial would reflect the metabolic cost of initiating and propagating leg swing during normal walking. We also reasoned that a lower muscle activity with these assisting forces would indicate which muscles are normally responsible for initiating and propagating leg swing. With a propulsive force at the waist of 10% body weight (BW), the net metabolic cost of walking decreased to 58% of normal walking. With the optimal combination, a propulsive force at the waist of 10% BW plus a pulling force at the feet of 3% BW the net metabolic cost of walking further decreased to 48% of normal walking. With the same combination, the muscle activity of the iliopsoas and rectus femoris muscles during the swing phase was 27 and 60% lower, respectively, but the activity of the medial gastrocnemius and soleus before swing did not change. Thus our data indicate that approximately 10% of the net metabolic cost of walking is required to initiate and propagate leg swing. Additionally, the hip flexor muscles contribute to the initiation and propagation leg swing.

Electromyography↗
PubMed2002

Relative contributions of balance and voluntary leg-coordination deficits to cerebellar gait ataxia.

Different cerebellar regions participate in balance control and voluntary limb coordination, both of which might be important for normal bipedal walking. We wanted to determine the relative contributions of balance versus leg-coordination deficits to cerebellar gait ataxia in humans. We studied 20 subjects with cerebellar damage and 20 control subjects performing three tasks: a lateral weight-shifting task to measure balance, a visually guided stepping task to measure leg- coordination, and walking. We recorded three-dimensional joint position data during all tasks and center of pressure coordinates during weight-shifting. Each cerebellar subject was categorized as having no detectable deficits, a balance deficit only, a leg-placement deficit only, or both deficits. We then determined the walking abnormalities associated with each of these categories. Five of 10 measures of gait ataxia were abnormal in cerebellar subjects with a balance deficit, but only 1 was abnormal in cerebellar subjects with a leg-placement deficit. Furthermore, subjects with a balance deficit performed worse than subjects with a leg-placement deficit on 9 of the 10 gait measures. Finally, performance on the balance task, but not the leg-placement task, explained a significant proportion of the variance in walking speed for the entire cerebellar group. We conclude that balance deficits are more closely related to cerebellar gait ataxia than leg-placement deficits. Our findings are consistent with animal literature, which has suggested that cerebellar control of balance and gait are interrelated, and dissociable from cerebellar control of voluntary, visually guided limb movements.

Adult↗
PubMed1997

Fifteen years of experience in treating 2177 episodes of foot and leg lesions with the circulator boot. Results of treatments with the circulator boot.

OBJECTIVE: To determine the clinical effectiveness of the end-diastolic pneumatic compression boot and of local antibiotics in treating limb lesions associated with diabetes and peripheral arterial, venous, and neuropathic disease. RESEARCH DESIGN AND METHODS: Office and hospital data were kept over 15 years on 2177 episodes of leg problems classified by the Wagner method for 1514 legs of 1035 patients largely referred because of failure of standard therapies. The fate of the untreated legs served as a controls when possible. RESULTS: Healing or improvement of treated legs was seen above that in the literature in all Wagner categories and was significant (P < 0.001) compared to the "control" leg, which deteriorated in 38.7% of patients. Significant risk factors against a successful outcome included smoking, inability to walk, increased home distance from the boot center, loss to treatment, hemodialysis, a Wagner 4-5 classification, inoperable iliac occlusions, vascular procedures before or after referral for boot therapy, and an aggressive vascular surgeon. Neuropathy allowed successful treatment of lesions nondiabetic patients could not tolerate. Relapse was significantly more frequent in arteriosclerosis obliterans (ASO) patients with diabetes than without diabetes and in patients with neuropathy than in those with ASO. Diabetes did not affect the relapse rate in stasis disease. The overall percentage of legs having major amputations was low: 2.5% for diabetic legs at the initial treatment episode, 1.6% at the time of a relapse, and 4.1% after seeking treatment elsewhere. For nondiabetic patients, the respective risks were similar: 2.0%, 1.2%, and 2.9%.

Aged↗