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Biomedical subjects

K Aminian

Publications and source records attributed to K Aminian.

12 recordsLinked to original sources
PubMed2006

A new ambulatory system for comparative evaluation of the three-dimensional knee kinematics, applied to anterior cruciate ligament injuries.

The aim of this study was to develop an ambulatory system for the three-dimensional (3D) knee kinematics evaluation, which can be used outside a laboratory during long-term monitoring. In order to show the efficacy of this ambulatory system, knee function was analysed using this system, after an anterior cruciate ligament (ACL) lesion, and after reconstructive surgery. The proposed system was composed of two 3D gyroscopes, fixed on the shank and on the thigh, and a portable data logger for signal recording. The measured parameters were the 3D mean range of motion (ROM) and the healthy knee was used as control. The precision of this system was first assessed using an ultrasound reference system. The repeatability was also estimated. A clinical study was then performed on five unilateral ACL-deficient men (range: 19-36 years) prior to, and a year after the surgery. The patients were evaluated with the IKDC score and the kinematics measurements were carried out on a 30 m walking trial. The precision in comparison with the reference system was 4.4 degrees , 2.7 degrees and 4.2 degrees for flexion-extension, internal-external rotation, and abduction-adduction, respectively. The repeatability of the results for the three directions was 0.8 degrees , 0.7 degrees and 1.8 degrees . The averaged ROM of the five patients' healthy knee were 70.1 degrees (standard deviation (SD) 5.8 degrees), 24.0 degrees (SD 3.0 degrees) and 12.0 degrees (SD 6.3 degrees for flexion-extension, internal-external rotation and abduction-adduction before surgery, and 76.5 degrees (SD 4.1 degrees), 21.7 degrees (SD 4.9 degrees) and 10.2 degrees (SD 4.6 degrees) 1 year following the reconstruction. The results for the pathologic knee were 64.5 degrees (SD 6.9 degrees), 20.6 degrees (SD 4.0 degrees) and 19.7 degrees (8.2 degrees) during the first evaluation, and 72.3 degrees (SD 2.4 degrees), 25.8 degrees (SD 6.4 degrees) and 12.4 degrees (SD 2.3 degrees) during the second one. The performance of the system enabled us to detect knee function modifications in the sagittal and transverse plane. Prior to the reconstruction, the ROM of the injured knee was lower in flexion-extension and internal-external rotation in comparison with the controlateral knee. One year after the surgery, four patients were classified normal (A) and one almost normal (B), according to the IKDC score, and changes in the kinematics of the five patients remained: lower flexion-extension ROM and higher internal-external rotation ROM in comparison with the controlateral knee. The 3D kinematics was changed after an ACL lesion and remained altered one year after the surgery.

Adult↗
PubMed2005

Dual-task-related gait changes in the elderly: does the type of cognitive task matter?

Dual-task-related gait changes among older adults while they perform spoken verbal tasks have been reported frequently. The authors examined whether the type of walking-associated spoken verbal task matters for dual-task-related gait changes in 16 older adults classified as transitionally frail. Mean stride time increased significantly when they walked and performed an arithmetic or a verbal fluency task compared with when they only walked (p < .001), whereas the coefficients of variation increased significantly only when they walked and performed the arithmetic task (p = .005) but not the verbal fluency task (p = .134). Those findings suggest that stride time variability under a dual-task condition depends on the type of walking-associated spoken verbal task.

Adult↗
PubMed2004

Ambulatory system for the quantitative and qualitative analysis of gait and posture in chronic pain patients treated with spinal cord stimulation.

The physical activity in normal daily life is determined to a large extent by the functional ability of a subject. As a result, the measurement of the physical activity that a subject performs spontaneously could be a useful and objective measurement of disability, particularly in patients with disease-related functional impairment. The aim of this study is to provide an accurate method for the measurement and analysis of the physical activity under normal life conditions. Using three kinematical sensors strapped to the body, both the posture and the gait parameters can be assessed qualitatively and quantitatively. A detailed description of the algorithms used to analyse both the posture and the gait are presented in this paper. Two methods, based on different sensor configurations and signal processing, are proposed for the detection of sitting and standing postures (Methods P1 and P2). Two other methods are used for the quantitative assessment of walking (Methods W1 and W2). The performance of the algorithms (expressed in terms of sensitivity, specificity and error) is based on the comparison of data recorded simultaneously by a non-interfering observer (reference data) with the data provided by the recording system (21 patients, 61 h). Sensitivity and specificity are respectively 98.2% and 98.8% (P1), 97.8% and 98.1% (P2) for sitting; 98.0% and 98.5% (P1), 97.4% and 97.8% (P2) for standing; 97.1% and 97.9% (W1), 92.4% and 94.9% (W2) for walking; and finally, 99.2% and 98.6% for lying. Overall detection errors (as a percent of range) are as follows: 1.15% (P1) and 1.20% (P2) for sitting, 1.36% (P1) and 1.40% (P2) for standing, 1.20% (W1) and 1.60% (W2) for walking and 0.40% for lying. The error for the estimated walking distance and the speed is 6.8% and 9.6%, respectively. We conclude that both methods can be used for the accurate measurement of the basic physical activity in normal daily life. Measurements performed before and after the delivery of a treatment can therefore provide information of unprecedented accuracy and objectivity on the ability of a procedure, in this case spinal cord stimulation, to restore functional capabilities.

Adult↗
PubMed2004

Evaluation of an ambulatory system for gait analysis in hip osteoarthritis and after total hip replacement.

Spatial and temporal parameters of gait have clinical relevance in the assessment of motor pathologies, particularly in orthopaedics. A new gait analysis system is proposed which consists of (a) an ambulatory device (Physilog) including a set of miniature gyroscopes and a portable datalogger, and (b) an algorithm for gait analysis. The aim of this study was the validation of this system, for accuracy and clinical applicability. Eleven patients with coxarthrosis, eight patients with total hip arthroplasty and nine control subjects were studied using this portable system and also a reference motion analyzer and force plate. The small differences in the stance period (19 +/- ms), stride length and velocity (0.4 +/- 9.6 cm and 2.5 +/- 8.3 cm/s, respectively), as well as thigh and shank rotations (2.4 +/- 4.3 degrees and 0.3 +/- 3.3 degrees, respectively), confirmed good agreement of the proposed system with the reference system. In addition, nearly the same accuracy was obtained for all three groups. Gait analysis based on Physilog was also in agreement with their Harris Hip Scores (HHS): the subjects with lower scores had a greater limp, a slower walking speed and a shorter stride. This ambulatory gait analysis system provides an easy, reproducible and objective method of quantifying changes in gait after joint replacement surgery for coxarthrosis.

Aged↗
PubMed2003

Elevated heels and adaptation to new shoes in frail elderly women.

Footwear is supposed to have influence on postural control and is a potential aspect to address in the prevention of falls in the elderly. This study aimed to show whether measurements of static balance and gait are different with habitual shoes compared to new special senior shoes with different heel height and whether these results change after adaptation. In a randomized controlled intervention study, 26 subjects (median age 87 years) were recruited from two nursing homes and one facility of assisted living. Measurements of static balance and gait were performed with habitual shoes and two types of new special senior shoes differing in heel height. Measurements were repeated after five weeks. There was no difference in static balance and gait with habitual shoes compared to either of the new footwear offered. Results of performance with higher heels were not different compared to lower heels. No further effect of adaptation after wearing a new shoe over five weeks could be demonstrated. With respect to static and dynamic balance, there seems to be a wide range of acceptable footwear as long as the heel height is below a critical value. A standardized shoe can be used in the assessment of balance because the effect of adaptation can be neglected.

Accidental Falls↗
PubMed2001

Can accelerometry accurately predict the energy cost of uphill/downhill walking?

To evaluate whether an activity monitor based on body acceleration measurement can accurately assess the energy cost of the human locomotion, 12 subjects walked a combination of three different speeds (preferred speed +/- 1 km/h) and seven slopes (-15 to +15% by steps of 5%) on a treadmill. Body accelerations were recorded using a triaxial accelerometer attached to the low back. The mean of the integral of the vector magnitude (norm) of the accelerations (mIAN) was calculated. VO2 was measured using continuous indirect calorimetry. When the results were separately analysed for each incline, mIAN was correlated to VO2 (average r = 0.87, p<0.001, n = 36). VO2 was not significantly correlated to mIAN when data were globally analysed (n = 252). Large relative errors occurred when predicted VO2 (estimated from data of level walking) was compared with measured VO2 for different inclines (-53% at +15% incline, to +55% at -15% incline). It is concluded that without an external measurement of the slope, the standard method of analysis of body accelerations cannot accurately predict the energy cost of uphill or downhill walking.

Acceleration↗
PubMed1999

Physical activity monitoring based on accelerometry: validation and comparison with video observation.

The objective of this feasibility study is to evaluate the use of the 'Physilog' device, an ambulatory physical-activity recorder based on acceleration measurement, for the monitoring of daily physical activities. Accelerations measured at the level of the chest and the thigh are recorded by Physilog over a period of 1 h in five normal subjects. A specially designed studio-like room allowing the performance of most usual activities of everyday life is used. A video film synchronised with the Physilog is obtained for each subject to check the accuracy of the data derived from Physilog. Based on the analysis on the average and the deviation of the acceleration signal, an algorithm is developed to classify the activities in four categories, i.e. lying, sitting, standing and locomotion. Compared with the video observations, the results from the algorithm show an overall misclassification of 10.7%, which is mainly due to confusion between dynamic activities and the standing posture. In contrast, the misclassification between postures is negligible. It is concluded that Physilog can be used in the clinical setting for the reliable measurement and long-term recording of most usual physical activities.

Activities of Daily Living↗
PubMed1999

Temporal feature estimation during walking using miniature accelerometers: an analysis of gait improvement after hip arthroplasty.

A new method for the detection of gait cycle phases using only two miniature accelerometers together with a light, portable digital recorder is proposed. Each subject is asked to walk on a walkway at his/her own preferred speed. Gait analysis was performed using an original method of computing the values of temporal parameters from accelerometer signals. First, to validate the accelerometric method, measurements are taken on a group of healthy subjects. No significant differences are observed between the results thus obtained and those from pressure sensors attached under the foot. Then, measurements using only accelerometers are performed on a group of 12 patients with unilateral hip osteo-arthritis. The gait analysis is carried out just before hip arthroplasty and again, three, six and nine months afterwards. A mean decrease of 88% of asymmetry of stance time and especially a mean decrease of 250% of asymmetry of double support time are observed, nine months after the operation. These results confirm the validity of the proposed method for healthy subjects and its efficiency for functional evaluation of gait improvement after arthroplasty.

Acceleration↗
PubMed1999

The prediction of speed and incline in outdoor running in humans using accelerometry.

PURPOSE: To explore whether triaxial accelerometric measurements can be utilized to accurately assess speed and incline of running in free-living conditions. METHODS: Body accelerations during running were recorded at the lower back and at the heel by a portable data logger in 20 human subjects, 10 men, and 10 women. After parameterizing body accelerations, two neural networks were designed to recognize each running pattern and calculate speed and incline. Each subject ran 18 times on outdoor roads at various speeds and inclines; 12 runs were used to calibrate the neural networks whereas the 6 other runs were used to validate the model. RESULTS: A small difference between the estimated and the actual values was observed: the square root of the mean square error (RMSE) was 0.12 m x s(-1) for speed and 0.014 radiant (rad) (or 1.4% in absolute value) for incline. Multiple regression analysis allowed accurate prediction of speed (RMSE = 0.14 m x s(-1)) but not of incline (RMSE = 0.026 rad or 2.6% slope). CONCLUSION: Triaxial accelerometric measurements allows an accurate estimation of speed of running and incline of terrain (the latter with more uncertainty). This will permit the validation of the energetic results generated on the treadmill as applied to more physiological unconstrained running conditions.

Analysis of Variance↗
PubMed1995

Incline, speed, and distance assessment during unconstrained walking.

Body accelerations during human walking were recorded by a portable measuring device. A new method for parameterizing body accelerations and finding the pattern of walking is outlined. Two neural networks were designed to recognize each pattern and estimate the speed and incline of walking. Six subjects performed treadmill walking followed by self-paced walking on an outdoor test circuit involving roads of various inclines. The neural networks were first "trained" by known patterns of treadmill walking. Then the inclines, the speeds, and the distance covered during overground walking (outdoor circuit) were estimated. The results show a good agreement between actual and predicted variables. The standard deviation of estimated incline was less than 2.6% and the maximum of the coefficient of variation of speed estimation is 6%. To the best of our knowledge, these results constitute the first assessment of speed, incline and distance covered during level and slope walking and offer investigators a new tool for assessing levels of outdoor physical activity.

Adult↗
PubMed1993

Real-time measurement of the contribution of the muscular activity to the metabolic rate in freely moving rats.

A new real-time ergometric system, ERGORAT, for measuring the energy expenditure due to muscular activity of small mammals is described. The method is based on measuring the vibrations induced by a freely moving rat to a platform on which it is living. Six accelerometers placed on the platform detect all the vibrations produced by the rat. The co-ordinates of the centre of mass of the animal are located by an optoelectronic device. This location and the six accelerations are fed to a microprocessor-based data acquisition and processing system. Using a Lagrangian dynamic model, the values of the mechanical energy transferred to the platform are computed every second. ERGORAT is used as part of an experimental setup allowing the measurement of the energetic balance of lean and obese rats. The results clearly show that the increase in metabolic rate of obese rats during cold exposure can be entirely explained by the cost of their increase in locomotor activity, whereas for lean rats, this cost accounts for only 41.5 per cent of their metabolic increase, the remaining being the contribution of their active brown adipose tissue.

Animals↗