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At least 253 records · Page 14Linked to original sources
PubMed2002

Compensatory gait mechanics in patients with unilateral knee arthritis.

OBJECTIVE: Few studies exist on gait adaptation caused by knee osteoarthritis (OA), and those have only explored adaptations of the kinematics and kinetics of the knee joint itself. We characterize ankle, knee, hip, and low back mechanical energy expenditures (MEE) and compensations (MEC) during gait in patients with knee OA. METHODS: Thirteen elderly patients with unilateral knee OA and 10 matched healthy elderly controls were studied during preferred and paced speed gait. Gait speed, step length, and lower extremity and low back joint MEE and MEC were compared between groups. RESULTS: Patients with knee OA had lower, but not significantly different, walking speed and step length compared to the controls, and had significantly different joint kinetic profiles. Patients had reduced ankle power at terminal stance, lacked a second positive peak in knee power, and had increased power absorption at the hip. Abnormal knee kinematics were exaggerated when walking at a paced speed, but hip kinetics normalized among patients with OA. CONCLUSION: Reduced ankle plantar-flexion power in patients with knee OA was probably due to disrupted transfer of energy through the knee. Lack of concentric knee power supports prior studies' conclusions that patients with knee OA avoid using their quadriceps to stabilize the knee, probably to reduce articular loads. Patients with knee OA increase eccentric hip power due to increased hip extension caused by abnormal knee kinematics, potentially increasing hip articular forces. This passive mechanism, however, may assist in the advancement of the leg into swing phase.

Adaptation, Physiological↗
PubMed2002

Microprocessor-based ambulatory activity monitoring in stroke patients.

PURPOSE: Recovery of ambulatory function after stroke is routinely assessed using standardized subject- or observer-rated instruments that do not directly measure ambulatory activities in the home-community setting. Accuracy of conventional pedometers in stroke patients is not established, limiting their application in mobility outcomes monitoring. This study investigates the accuracy and reliability of a mechanical pedometer versus microprocessor-based step activity monitoring (SAM) in gait-impaired hemiparetic stroke patients. METHODS: Accuracy and test-retest reliability of ankle-worn SAM and belt-worn pedometer were tested directly against hand tallied stride counts and cadence during a battery of timed walks in 16 chronic hemiparetic stroke patients. Patients performed replicate 1-min floor walks at self-selected and fastest comfortable paces, and two 6-min walks on separate days. RESULTS: SAM cadence and total stride counts are more accurate than pedometers during 1-min walks at self-selected (99 +/- 1 vs 87 +/- 11.3%, mean +/- SD, P < 0.01); fast pace (98 +/- 2.3% vs 85 +/- 15%, P < 0.01); and repeated 6-min walks performed on separate days (99 +/- 1% vs 89 +/- 12%, P < 0.01). Although SAM is highly reliable (r = 0.97, P < 0.0001) and accurate in all patients under every walking condition tested, the mechanical pedometer demonstrates this high level of accuracy in only half of stroke patients and has poor test-retest reliability (r = 0.64, P < 0.05). CONCLUSION: SAM, but not the conventional pedometer, provides accurate and reliable measures of cadence and total stride counts in hemiparetic stroke patients. Portable microprocessor-based gait monitoring offers potential to quantitatively measure home-community-based ambulatory activity levels in this population.

Gait↗
PubMed1993

Initial experience with a new single chamber, dual sensor rate responsive pacemaker. The Topaz Study Group.

In August 1991, a new single chamber pacemaker became available that utilizes information from two sensors, activity and stimulus-to-T wave (QT) interval. We are reporting on the first 90 implants in 21 centers. T wave sensing was adequate at implantation in 88/90 patients, with a safety margin of > 100% in 86/90. Activity sensing was adequate in all patients. The contribution of each sensor (sensor blending) is programmable for each patient. Of 75 patients assessed at 1 month after implant, three have been programmed to "Activity-Only" mode, and 72 to dual sensor mode. Of these, 18 have been programmed to "QT < Activity," 48 to "QT = Activity," and 6 to "QT > Activity." Forty-five patients underwent exercise testing in dual sensor mode and a subgroup of 15 also underwent exercise testing in Activity-Only mode. The dual sensor mode produced a more gradual increase in pacing rate. Sensor Cross Checking satisfactorily prevented a sustained high pacing rate in tests of false-positive activity sensing (tapping, vibrating pacemaker, or static pressure). The maximum pacing rate on walking downstairs (94.2 +/- 7.2 ppm) was similar to that produced by walking upstairs (91.6 +/- 5.9 ppm). We conclude that initial assessment of this dual sensor, single chamber, rate responsive pacemaker confirms that the algorithm for combining data from two sensors functions satisfactorily. Dual sensor rate responsive pacing may offer significant advantages over single sensor devices, and further studies of this novel device are indicated.

Adolescent↗
PubMed1989

Physiological determinants of race walking performance in female race walkers.

The purpose of this study was to determine the relationship between race pace on a 5 km walking performance and velocity at the lactate threshold (V-LT), VO2 at the lactate threshold (VO2-LT), velocity at which blood lactate corresponded to 4 mM level (V-OBLA), VO2 at which blood lactate corresponded to 4 mM level (VO2-OBLA), walking economy (steady state VO2 at a standard velocity) and maximal oxygen uptake (VO2max) in eight female race walkers. A multiple stepwise linear regression analysis was employed to predict the race pace on a 5 km walking performance as dependent variable. Since V-OBLA was highly correlated to 5 km race walking performance (r = 0.94, P less than 0.001), it was selected as the first predictor. When VO2max was added to V-OBLA as the second predictor the predictive accuracy increased significantly, but multiple R did not increase significantly by adding variables of walking economy or other parameters as independent variance. As a result, the combination of V-OBLA and VO2max as independent variables accounted for the greatest amount of total variance (97 per cent). It is suggested that blood lactate variable such as V-OBLA can account for a large portion of the variance in race pace on a 5 km walking performance.

Adult↗
PubMed1981

Mechanics and energetics of stilt walking.

Three subjects were studied walking on a sports track with and without 1-m-long stilts. They were asked to walk in different ways. Pace length, step rate, heart rate, and oxygen consumption were measured under both conditions at different speeds. The results show that walking speed is generally faster for stilt walking than for normal walking. The higher speed is achieved due to increased pace length in spite of a decrease in step rate. The relationship between energy expenditure and walking speed is approximately the same in both cases. This result may be explained by two opposing factors: increase of pace length and decrease of step rate decrease the energy requirements of stilt walking, but the foot loading presented by the stilt walking exaggerates these conditions and increases energy expenditure.

Biomechanical Phenomena↗
PubMed1993

The CAT-CAM socket and quadrilateral socket: a comparison of energy cost during ambulation.

Twenty unilateral trans-femoral amputees fitted with either the Contoured Adducted Trochanteric-Controlled Alignment Method (CAT-CAM) socket (n = 10) or the quadrilateral (QUAD) socket (n = 10), and a "non-amputee" control group (n = 10) participated in the study. Subjects meeting the following criteria were studied: healthy males between the ages of 18 and 55 years, amputation due to non-vascular pathology, an unaffected sound limb, at least six months use of the test prosthesis, and a minimal stump length of 15 cm. Subjects ambulated in two randomized trials separated by 20 minutes of rest at 2 assigned speeds: a pace reflecting normal walking speed (97 m/min = 2.5 mph) or a slower speed (48.5 m/min = 1.25 mph). Heart rate (HR) and Oxygen uptake (VO2) measured during steady state walking were analyzed via two-way ANOVA. Differences among means were further analyzed using Tukey post hoc and simple effects tests. Significant differences were observed between the control group and CAT-CAM subjects with respect to VO2 (p < 0.05) and HR (p < 0.01) at the slower speed. The control group and subjects using the QUAD socket also differed with respect to VO2 (p < 0.01) and HR (p < 0.01) at the slower pace. Faster pace required more energy expenditure (p < 0.01) and produced higher HR (p < 0.01) than slower speeds. At faster pace, a significantly higher energy expenditure in the QUAD than the CAT-CAM group was observed (p < 0.01). It is concluded that ambulating at normal pace using the CAT-CAM socket design uses less energy than when using a QUAD socket design.

Adolescent↗
PubMed1999

Trunk kinematics in hemiplegic gait and the effect of walking aids.

OBJECTIVE: To establish baseline measurements of trunk movements during hemiplegic gait, to assess the relationship between trunk movements and walking ability, and to investigate the effect of walking aids on the trunk movements. METHOD: Twenty subjects with a chronic hemiplegia from a stroke, who could walk independently, were recruited. Lateral and vertical movements of the pelvis, and symmetry of these movements were measured using CODA (a three-dimensional movement analysis system) as the subjects walked at their own pace without an aid. They were also tested as they walked with a stick and a tripod to assess the effect of different walking aids. Mean values for the trunk movements and symmetry were calculated, Pearson's correlations assessed the relationship between each trunk movement and gait velocity (a measure of overall walking ability), and the influence of the different aids was assessed using a one-way repeated measures ANOVA. RESULTS: Lateral displacement was large (mean = 9.9 cm, SD 3.9) and orientated to the sound side, vertical displacement was small (mean = 2.45 cm, SD 1.4). The movements showed marked asymmetry which favoured the hemiplegic side in that there was less movement of, or towards this side. There was a significant relationship (at 5% level) between walking ability and lateral movements (r = 0.6), but not vertical movements (r= 0.41). No significant differences were found with the different aids. CONCLUSION: These results give baseline values for trunk movements during hemiplegic gait and the relationship between the movements and walking ability. The use of walking aid and the type of walking aid did not affect the subjects' trunk movements or walking ability.

Biomechanical Phenomena↗
PubMed1997

Neural control of interlimb oscillations. II. Biped and quadruped gaits and bifurcations.

Behavioral data concerning animal and human gaits and gait transitions are simulated as emergent properties of a central pattern generator (CPG) model. The CPG model is a version of the Ellias-Grossberg oscillator. Its neurons obey Hodgkin-Huxley type equations whose excitatory signals operate on a faster time scale than their inhibitory signals in a recurrent on-center off-surround anatomy. A descending command or GO signal activates the gaits and triggers gait transitions as its amplitude increases. A single model CPG can generate both in-phase and anti-phase oscillations at different GO amplitudes. Phase transitions from either in-phase to anti-phase oscillations or from anti-phase to in-phase oscillations can occur in different parameter ranges, as the GO signal increases. Quadruped vertebrate gaits, including the amble, the walk, all three pairwise gaits (trot, pace, and gallop), and the pronk are simulated using this property. Rapid gait transitions are simulated in the order--walk, trot, pace, and gallop--that occurs in the cat, along with the observed increase in oscillation frequency. Precise control of quadruped gait switching uses GO-dependent modulation of inhibitory interactions, which generates a different functional anatomy at different arousal levels. The primary human gaits (the walk and the run) and elephant gaits (the amble and the walk) are simulated, without modulation, by oscillations with the same phase relationships but different waveform shapes at different GO signal levels, much as the duty cycles of the feet are longer in the walk than in the run. Relevant neural data from spinal cord, globus pallidus, and motor cortex, among other structures, are discussed.

Animals↗
PubMed2005

Reliability of simple portable tests of physical performance in older people after hip fracture.

OBJECTIVE: To investigate the test-retest reliability of measures of strength, balance, gait and functional performance when used with older people following hip fracture. SUBJECTS: Thirty people (16 hospital inpatients and 14 community dwellers). DESIGN: Subjects underwent two assessments: one day apart for the hospital inpatients and one week apart for the community dwellers. MEASUREMENT: Strength (dynamometer, sphygmomanometer, spring balance, lateral step-up ability), balance (sway-meter, Functional Reach Test, single leg stance time, Step Test), gait (timed 6-m walk with steps taken, base of support and step length), and functional performance (PPME total score and timed supine-to-sit and sit-to-stand) were measured. RESULTS: Eleven of the 14 continuously scaled measurement tools achieved excellent reliability (intraclass correlation coefficient (ICC) > 0.75) for one or more tests. A hand-held dynamometer was found to be the tool with the highest test-retest reliability for measuring hip muscle strength (ICC (3,1) 0.86 for affected hip abduction). For measurement of knee extension strength, a spring balance (ICC (3,1) 0.94 affected leg) was the most reliable. For testing balance, the Step Test (ICC (3,1) 0.94 for stepping with affected leg) and Functional Reach Test (ICC (3,1) 0.89) had the highest test-retest reliability. The ICC (3,1) values were 0.97 for walking velocity (comfortable pace) and 0.96 for the total score of the Physical Performance and Mobility Examination. CONCLUSION: The test-retest reliability of a number of simple measures of physical performance is excellent when used with this population.

Aged↗
PubMed1999

Symmetry in locomotor central pattern generators and animal gaits.

Animal locomotion is controlled, in part, by a central pattern generator (CPG), which is an intraspinal network of neurons capable of generating a rhythmic output. The spatio-temporal symmetries of the quadrupedal gaits walk, trot and pace lead to plausible assumptions about the symmetries of locomotor CPGs. These assumptions imply that the CPG of a quadruped should consist of eight nominally identical subcircuits, arranged in an essentially unique matter. Here we apply analogous arguments to myriapod CPGs. Analyses based on symmetry applied to these networks lead to testable predictions, including a distinction between primary and secondary gaits, the existence of a new primary gait called 'jump', and the occurrence of half-integer wave numbers in myriapod gaits. For bipeds, our analysis also predicts two gaits with the out-of-phase symmetry of the walk and two gaits with the in-phase symmetry of the hop. We present data that support each of these predictions. This work suggests that symmetry can be used to infer a plausible class of CPG network architectures from observed patterns of animal gaits.

Animals↗
PubMed2006

Validity and reliability of the modified shuttle walk test in patients with chronic obstructive pulmonary disease.

OBJECTIVES: (1) To examine the concurrent criterion validity of the modified shuttle walk test (MSWT) by using the 6- (6MWT) and 12-minute walk test (12MWT), (2) to examine the concurrent criterion validity of the estimated maximum oxygen uptake (Vo2max) of the MSWT with actual Vo2max, and (3) to determine test-retest reliability of the MSWT in patients with chronic obstructive pulmonary disease (COPD). DESIGN: Validation study. SETTING: Outpatient pulmonary rehabilitation program. PARTICIPANTS: Thirty clinically stable adults with COPD. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Subjects were randomly assigned to receive either the 6MWT and 12MWT or the MSWT first. The MSWT was repeated 1 week later (N = 30). Estimated Vo2max was calculated, and actual Vo2max was conducted by using the Jones test. Validity of the MSWT was assessed by comparing endurance scores and Vo2max with results from the 6MWT and 12MWT and Jones test, respectively. RESULTS: There was a moderately high correlation between the MSWT and the 6MWT and 12MWT at initial testing (.82 and .74, respectively). Correlation between estimated and actual Vo2max was r equal to .68. Test-retest reliability for the entire sample was high (intraclass correlation coefficient, .88). Results remained quite stable across severity, age, and sex subgroups. CONCLUSIONS: The MSWT is a standardized externally paced submaximal endurance walking test. The results indicate that the MSWT has high concurrent validity and test-retest reliability for patients with COPD.

Aged↗
PubMed2001

Models of central pattern generators for quadruped locomotion. I. Primary gaits.

In this paper we continue the analysis of a network of symmetrically coupled cells modeling central pattern generators for quadruped locomotion proposed by Golubitsky, Stewart, Buono, and Collins. By a cell we mean a system of ordinary differential equations and by a coupled cell system we mean a network of identical cells with coupling terms. We have three main results in this paper. First, we show that the proposed network is the simplest one modeling the common quadruped gaits of walk, trot, and pace. In doing so we prove a general theorem classifying spatio-temporal symmetries of periodic solutions to equivariant systems of differential equations. We also specialize this theorem to coupled cell systems. Second, this paper focuses on primary gaits; that is, gaits that are modeled by output signals from the central pattern generator where each cell emits the same waveform along with exact phase shifts between cells. Our previous work showed that the network is capable of producing six primary gaits. Here, we show that under mild assumptions on the cells and the coupling of the network, primary gaits can be produced from Hopf bifurcation by varying only coupling strengths of the network. Third, we discuss the stability of primary gaits and exhibit these solutions by performing numerical simulations using the dimensionless Morris-Lecar equations for the cell dynamics.

Animals↗
PubMed2004

Validation of the Late-Life Function and Disability Instrument.

OBJECTIVES: To assess the concurrent and predictive validity of the Late-Life Function and Disability Instrument (LLFDI). DESIGN: Cross-sectional. SETTING: University-based human physiology laboratory. PARTICIPANTS: One hundred one men and women aged 80.8 +/- 0.4. MEASUREMENTS: A short physical performance battery (SPPB) and a self-paced 400-m walk (400-m W) were used as performance tests of lower extremity function. The LLFDI was used to assess self-reported function and physical disability. Partial correlations adjusted for age and body mass index were used to determine the concurrent and predictive validity of the LLFDI. Statistical significance was accepted at P<.004 using a testwise correction. RESULTS: LLFDI Overall Function scores were moderately associated with the SPPB (r=0.65, P<.001), 400-m W gait speed (r=0.69, P<.001), and measures of lower extremity function. Correlations of the two lower extremity subscores of the LLFDI (correlation coefficient (r)=0.63-0.73, P<.001) were greater than for the LLFDI upper extremity subscores (r=0.19-0.26, P>.004). Performance measures of function predicted disability limitations in the range of r=0.37-0.44 (P<.001) and disability frequency in the range of r=0.16-0.20 (P>.004). CONCLUSION: These findings support the concurrent and predictive validity of the LLFDI. Results support the use of the LLFDI scales as a substitute for physical performance tests when self-report is a preferred data-collection format.

Activities of Daily Living↗
PubMed1991

Randomised controlled trial of the effectiveness of a respiratory health worker in reducing impairment, disability, and handicap due to chronic airflow limitation.

A randomised controlled trial was undertaken to determine whether a respiratory health worker was effective in reducing the respiratory impairment, disability, and handicap experienced by patients with chronic airflow limitation attending a respiratory outpatient department. The 152 adults (aged 30-75 years) who participated had a prebronchodilator forced expiratory volume in one second (FEV1) below 60% predicted and no other disease. They were randomised to receive the care of a respiratory health worker or the normal services provided by the outpatient department. The respiratory health worker provided health education and symptom and treatment monitoring in liaison with primary care services. After one year there was little difference between the two groups in spirometric values (FEV1 and forced vital capacity before and after salbutamol 200 micrograms), disability (six minute walking distance and paced step test), and handicap (sickness impact profile, hospital anxiety and depression scale). Patients not looked after by the respiratory health worker were more likely to die (relative risk 2.9 (95% confidence limits 0.8, 10.2); when age and FEV1 were controlled for this risk increased to 5.5 (95% confidence limits 1.2, 24.5). Patients looked after by the respiratory health worker attended their general practitioner more frequently and were prescribed a greater range of drugs. This is the third study to have found limited measurable benefit in terms of morbidity from the intervention of a respiratory health worker. This may be due to the ability of such workers to keep frail patients alive.

Adult↗
PubMed1975

In vivo measurement of bone strain in the horse.

Strain gauges were successfully bonded in vivo to the cranial, caudal, medial, and lateral aspects of the equine radium and tibia and to the dorsal, palmar, or plantar, medial, the lateral aspects of the metacarpus and metatarsus--all in the mid-diaphyseal region. Various activities were investigated, including walking, trotting or pacing, and standing up from anesthesia. The strain patterns showed that each stride produced a characteristic deformation cycle. The strains were measured and the axial loads were calculated as the horse performed certain activities. The tension band side of each bone was predicted from the results. The tension band sides of the metacarpus and metatarsus were the dorsomedial and dorsolateral aspects; for the radius and tibia, the tension band sides were the cranial and craniolateral aspects, respectively.

Animals↗
PubMedDate not supplied

[Modulated kinesitherapy in rehabilitation of patients with cardiovascular diseases].

Modulated kinesitherapy (MK) is a new method based on synchronization of vegetative and motor components in walking at a pace corresponding to actual heart rate which is maintained during the procedure with cardiotrainer Marafon. MK produced the following therapeutic effects: optimization of cardiovascular functions (weakening of postload on the heart with lowering of arterial pressure; improvement of coronary blood flow, stabilization of the heart rate and cardiac pump function); marked antiarrhythmic effect, normalization of autonomic nervous system tonicity, neurohumoral and psychoemotional state. MK is indicated in ischemic heart disease, essential hypertension, cardiac arrhythmia, vegetovascular asthenia.

Adult↗
PubMed1991

Responses to acute exercise and training after cardiac transplantation: a review.

Cardiac transplant patients now survive for several years, and the quality of life after recovery from the immediate operation is of increasing interest. The acute response to exercise depends mainly upon an increase of venous return (acting through the Frank-Starling mechanism) and slower chronotropic and inotropic responses to circulating catecholamines. At rest, there is some increase of heart rate and blood pressure, with a low normal cardiac output. During submaximal exercise the stroke volume is greater than normal, but the cardiac output is somewhat reduced, leading to a widening of arteriovenous oxygen difference. Peak heart rate, peak stroke volume, and peak cardiac output are all substantially reduced in the immediate postoperative period. Poor ventricular performance reflects in part an increase of afterloading associated with lean tissue loss. Endurance training restores lean tissue, with associated and probably causally related gains of cardiac function and peak oxygen transport. Exercise prescription after transplantation is commonly regulated by walking distance and pace, ventilatory and blood pressure responses, and ratings of perceived exertion, monitoring for episodes of infection and transplant rejection. There are psychological disturbances immediately following surgery, but again training appears to help ameliorate the mood state. Heterotopic transplants (in which donor and recipient hearts are conserved) generally yield a less satisfactory result than the standard orthotopic procedure. The ventilatory response to exercise is greater for a heart-lung transplant than for a cardiac transplant, but overall functional responses seem similar for the two types of patients. Patients tolerate exercise quite well after cardiac transplantation, and progressive endurance training is a helpful component of treatment in such individuals.

Exercise↗
PubMed2006

[Study on the performances of the positive pressure powered air-filter protective hood].

The positive pressure powered air-filter protective hood can prevent physicians and nurses from being infected by serious respiratory infections. The contaminated air is filtered by the high efficiency specific air-filter (HESA) and then transported into the hood by a blower to form about 140 +/- 10 Pa positive pressure environment, which makes the air in hood overflow out from the lower part of the hood, by which carbon dioxide and vapor can be removed, and excreted. The HESA's filters of simulative virus up to 99.9999% with the structure of double layers filtering. With going at 4 km/h pace on a walking vehicle wearing the hood, the testees' heart rate is 90-105/min oxygen saturation of the blood(SPO2) is 97%-98%. When the air flow is from 75 L/min to 125 L/min, this can meet the testees' physiological demand under heavy workload. Clinical trial results show that the hood can effectively protect the physicians and nurses from infection.

Adult↗