Lower-extremity biomechanics during forward and lateral stepping activities in older adults.
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OBJECTIVE: To characterize the lower-extremity biomechanics associated with stepping activities in older adults. DESIGN: Repeated-measures comparison of kinematics and kinetics associated with forward step-up and lateral step-up activities. BACKGROUND: Biomechanical analysis may be used to assess the effectiveness of various 'in-home activities' in targeting appropriate muscle groups and preserving functional strength and power in elders. METHODS: Data were analyzed from 21 participants (mean 74.7 yr (standard deviation, 4.4 yr)) who performed the forward and lateral step-up activities while instrumented for biomechanical analysis. Motion analysis equipment, inverse dynamics equations, and repeated measures ANOVAs were used to contrast the maximum joint angles, peak net joint moments, angular impulse, work, and power associated with the activities. RESULTS: The lateral step-up resulted in greater maximum knee flexion (P<0.001) and ankle dorsiflexion angles (P<0.01). Peak joint moments were similar between exercises. The forward step-up generated greater peak hip power (P<0.05) and total work (P<0.001); whereas, the lateral step-up generated greater impulse (P<0.05), work (P<0.01), and power (P<0.05) at the knee and ankle. CONCLUSIONS: In older adults, the forward step-up places greater demand on the hip extensors, while lateral step-up places greater demand on the knee extensors and ankle plantar flexors. RELEVANCE: Clinicians may use data from biomechanical analyses of in-home exercises to more effectively target specific lower-extremity muscle groups when prescribing exercise activities for older adults. The forward step-up is recommended for maintaining or improving hip extensor performance; whereas, the lateral step-up is recommended when targeting the knee extensors and ankle plantar flexors. (+info)
Usefulness of brachial-ankle pulse wave velocity measurement: correlation with abdominal aortic calcification.
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At present, brachial-ankle pulse wave velocity (baPWV) can be measured easily and noninvasively. We studied the correlation between aortic damage estimated by baPWV and that determined by measuring the length of abdominal aortic calcification (AAC) on X-ray films, which parameter has been significantly associated with cardiovascular morbidity and mortality. baPWV was measured using the form PWV/ankle brachial index (ABI) device in 97 patients free of end-stage renal failure or peripheral arterial disease. baPWV correlated significantly with age (r2=0.625, p<0.0001), was significantly higher in hypertensives than in normotensives (2,109+/-67 vs. 1,623+/-93 cm/s, p<0.0001), and correlated significantly with systolic blood pressure (r2=0.64, p<0.0001) and diastolic blood pressure (r2=0.397, p<0.0001). baPWV was significantly higher in diabetic patients than in nondiabetics (2,068+/-73 vs. 1,813+/-97 cm/s, p<0.05), but was similar in normolipidemic and hyperlipidemic patients. baPWV did not correlate with body mass index, fasting plasma glucose, total cholesterol, high density lipoprotein (HDL)-cholesterol, low density lipoprotein (LDL)-cholesterol or triglyceride levels, but correlated significantly with AAC length (r2=0.599, p<0.0001). Multiple regression analysis indicated that age, systolic blood pressure and AAC length were independent determinants of baPWV. Our results indicate that baPWV is useful for estimating aortic damage and could be a potentially useful predictor of vascular morbidity and mortality. (+info)
Patterned sensory stimulation induces plasticity in reciprocal ia inhibition in humans.
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Training of spinal cord circuits using sensorimotor stimulation has been proposed as a strategy to improve movement after spinal injury. How sensory stimulation may lead to long-lasting changes is not well understood. We studied whether sensory stimulation might induce changes in the strength of a specific spinal interneuronal circuit: spinally mediated reciprocal Ia inhibition. In healthy humans, the strength of reciprocal inhibition between ankle flexor and extensor muscles was assessed before and after 30 min of peroneal nerve stimulation at motor threshold intensity. Three stimulation protocols were assessed: patterned nerve stimulation (10 pulses at 100 Hz every 1.5 sec), uniform nerve stimulation (one pulse every 150 msec), and combined stimulation of the peroneal nerve and the motor cortex with transcranial magnetic stimulation. Short-latency reciprocal inhibition from ankle flexor to extensor muscles was measured by conditioning the soleus H-reflex with stimulation of the common peroneal nerve. The strength of the reciprocal inhibition was measured at baseline and for 20 min after each stimulation session. Patterned stimulation, with or without motor cortex stimulation, enhanced reciprocal inhibition for at least 5 min afterward. The uniform pattern of stimulation was ineffective. These results demonstrate the presence of short-term plasticity within spinal inhibitory circuits. We conclude that the pattern of sensory input is a crucial factor for inducing changes in the spinal circuit for reciprocal inhibition in humans. These findings may have implications for the use of repetitive patterned sensory stimulation in rehabilitative efforts to improve walking ability in patients with spinal injury. (+info)
Forearm hyperemia is a better marker than carotid intima-media thickness or ankle-brachial index for coronary artery disease in Japanese males under 65.
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Forearm hyperemia, carotid intima-media thickness (IMT), and ankle-brachial pressure index (ABI) are subclinical markers associated with coronary artery disease (CAD). However, it is not known which marker is most highly correlated with CAD. We therefore compared these three parameters in the same patients under 65 years of age. In 40 males with documented CAD (mean age, 53 years), we measured forearm hyperemia by plethysmography, carotid IMT by B-mode ultrasound, and ABI by Doppler ultrasonography. Microalbuminuria, serum lipids, glucose and C-reactive protein (CRP) were also measured. Thirteen normal males served as controls (mean age, 49 years). Compared with normal subjects, CAD patients had lower hyperemia (42 vs. 92%; p < 0.001) and greater carotid IMT (0.81 vs. 0.67 mm; p < 0.01), but ABI was similar. The sensitivity of forearm hyperemia (72%) was higher than that of carotid IMT (22%) or ABI (3%) (abnormal criteria: forearm hyperemia < 60%, carotid IMT 21.0 mm, and ABI < 0.9). The patients had higher serum low-density lipoprotein (LDL) cholesterol, glucose and CRP, and lower high-density lipoprotein (HDL) cholesterol than the controls. Albuminuria was present in 49% of patients. Subclinical markers were further analyzed by age (35-54 vs. 55-64 years). The sensitivity of carotid IMT was lower in the younger patients (4% vs. 33%), while that of forearm hyperemia (69% vs. 75%) and albuminuria (47% vs. 52%) did not change with age. While carotid ultrasound was useful in older patients ( > or = 55 years), forearm hyperemia and microalbuminuria were sensitive markers irrespective of age. ABI was not useful in the Japanese men with CAD under age 65. (+info)
Radiography of soft tissue of the foot and ankle with diffraction enhanced imaging.
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Non-calcified tissues, including tendons, ligaments, adipose tissue and cartilage, are not visible, for any practical purposes, with conventional X-ray imaging. Therefore, any pathological changes in these tissues generally necessitate detection through magnetic resonance imaging or ultrasound technology. Until recently the development of an X-ray imaging technique that could detect both bone and soft tissues seemed unrealistic. However, the introduction of diffraction enhanced X-ray imaging (DEI) which is capable of rendering images with absorption, refraction and scatter rejection qualities has allowed detection of specific soft tissues based on small differences in tissue densities. Here we show for the first time that DEI allows high contrast imaging of soft tissues, including ligaments, tendons and adipose tissue, of the human foot and ankle. (+info)
Late-term reconstruction of lateral ankle ligaments using a split peroneus brevis tendon graft (Colville's technique) in patients with chronic lateral instability of the ankle.
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We reviewed 14 patients with chronic lateral instability of the ankle treated by Colville's technique between 1996 and 2001. The mean patient age was 25 (20-35) years and all were men. The mean period between injury and surgery was 25 (18-32) months, and the mean follow-up was 20 (14-32) months. Twelve of the results were excellent and two were good according to the criteria of Chrisman and Snook. All patients returned to normal daily activity levels at an average of 6 months following surgery. (+info)
Localized irregularities in hemoglobin flow and oxygenation in calf muscle in patients with peripheral vascular disease detected with near-infrared spectrophotometry.
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PURPOSE: Near-infrared spectrophotometry is used to measure flow, concentration, and oxygenation of hemoglobin in arterioles, capillaries, and venules several centimeters deep in tissue. The purpose of this study was to investigate the distribution of flow, concentration, and oxygenation of hemoglobin in calf muscle in patients with documented peripheral arterial occlusive disease (PVD), patients with risk factors for PVD,and healthy younger subjects at rest. METHOD: With a frequency-domain near-infrared spectrophotometer and a specially designed probe, we generated maps at 22 locations simultaneously of hemoglobin flow, concentration, and oxygenation, with the venous occlusion method. Eight legs of 7 patients with diagnosed PVD (PVD group), 10 legs of 8 patients with normal ankle-brachial index but with risk factors for PVD (RF group), and 16 legs of 8 healthy subjects (H group) were studied. RESULTS: Global mean values were significantly (P <.05) different between the three groups for oxygen consumption (PVD group, 0.027 +/- 0.009 mL/100 g/min; RF group, 0.038 +/- 0.017 mL/100 g/min; H group, 0.022 +/- 0.020 mL/100 g/min), venous oxygen saturation (PVD, 59.7% +/- 15.4%; RF, 69.6% +/- 10.5%; H, 80.8% +/- 4.5%), and, at 60 s of venous occlusion, concentration changes in oxyhemoglobin (PVD, 4.48 +/- 3.25 micromol/L; RF, 8.44 +/- 2.33 micromol/L; H, 6.85 +/- 4.57 micromol/L), deoxyhemoglobin (PVD, 3.60 +/- 0.73 micromol/L; RF, 4.39 +/- 1.30 micromol/L; H, 2.36 +/- 1.79 micromol/L), and total hemoglobin (PVD, 8.07 +/- 3.83 micromol/L; RF, 12.83 +/- 2.75 micromol/L; H, 9.21 +/- 6.34 micromol/L). No significant difference was found between the three groups for hemoglobin flow (PVD, 0.92 +/- 0.69 micromol/100 mL/min; RF, 1.68 +/- 0.50 micromol/100 mL/min; H, 1.44 +/- 1.17 micromol/100 mL/min) and blood flow (PVD, 0.45 +/- 0.28 mL/100 g/min; RF, 0.77 +/- 0.21 mL/100 g/min; H, 0.62 +/- 0.50 mL/100 g/min). All parameters featured a distribution dependent on location. CONCLUSION: Mean value for venous oxygen saturation was higher in healthy subjects compared to patients with documented PVD. In patients with PVD, areas of lower oxygenation were clearly discernible. At distal locations of calf muscle, significant correlations between reduced hemoglobin flow, venous oxygen saturation, oxyhemoglobin, and total hemoglobin and reduced ankle-brachial index were found. Maps revealed localized irregularities in oxyhemoglobin, total hemoglobin, and venous oxygen saturation in patients with PVD. Near-infrared spectrophotometry is a noninvasive bedside technique that can enable determination of blood flow and oxygenation in tissue and may provide a method for evaluating patients with PVD. (+info)
Ankle-brachial blood pressure index predicts all-cause and cardiovascular mortality in hemodialysis patients.
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A reduction in ankle-brachial BP index (ABPI) is associated with generalized atherosclerotic diseases and predicts cardiovascular mortality and morbidity in several patient populations. However, a large-scale analysis of ABPI is lacking for hemodialysis (HD) patients, and its use in this population is not fully validated. A cohort of 1010 Japanese patients undergoing chronic hemodialysis was studied between November 1999 and May 2002. Mean age at entry was 60.6 +/- 12.5 yr, and duration of follow-up was 22.3 +/- 5.6 mo. Patients were stratified into five groups (< 0.9, > or = 0.9 to < 1.0, > or = 1.0 to < 1.1, > or = 1.1 to < 1.3, and > or = 1.3) by ABPI measured at entry by an oscillometric method. The frequency distribution of ABPI was 16.5% of patients < 0.9, 8.6% of patients > or = 0.9 to < 1.0, 16.9% of patients 1.0 > or = to < 1.1, and 47.0% of patients > or 1.1 to < 1.3, whereas 10.9% of patients had an abnormally high ABPI (> or = 1.3). The relative risk of a history of diabetes mellitus (DM), cardiovascular, and cerebrovascular disease was significantly higher in patients with lower ABPI than those with ABPI > or = 1.1 to <1.3. During the study period, 77 cardiovascular and 41 noncardiovascular fatal events occurred. On the basis of Cox proportional hazards regression analysis, ABPI emerged as a strong independent predictor of all-cause and cardiovascular mortality. After adjustment for confounding variables, the hazard ratio (HR) for ABPI < 0.9 was 4.04 (95% confidence interval, 2.38 to 6.95) for all-cause mortality and 5.90 (2.83 to 12.29) for cardiovascular mortality. Even those with modest reductions in the ABPI (> or = 0.9 to <1.1) appeared to be at increased risk. Patients having abnormally high ABPI (> or = 1.3) also had poor prognosis (HR, 2.33 [1.11 to 4.89] and 3.04 [1.14 to 8.12] for all-cause and cardiovascular mortality, respectively). Thus, the present findings validate ABPI as a powerful and independent predictor for all-cause and cardiovascular mortality among hemodialysis patients. (+info)