Biomedical subjects

Claudia Mazzà

Publications and source records attributed to Claudia Mazzà.

5 recordsLinked to original sources

PubMed2006

Biomechanic modeling of sit-to-stand to upright posture for mobility assessment of persons with chronic stroke.

OBJECTIVE: To test the suitability of using biomechanic measures associated with a minimum measured input model (MMIM) approach to assess mobility of people with chronic stroke during the execution of a sit-to-stand (STS) to upright posture motor task. DESIGN: Single group, observational. SETTING: Institutional settings in the United States and Italy. PARTICIPANTS: Twenty-nine subjects with chronic unilateral lower-limb impairments and resultant mobility limitations secondary to stroke. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Manual measurement of lower-limb strength; performance-based tests including repeated chair standing, walking speed, and standing balance; and ground reactions measured with a force platform during STS and upright posture. The ground reactions were fed to a telescopic inverted pendulum model of the musculoskeletal system. Parameters representing the model outputs were compared with performance-based and strength measures to assess, respectively, motor ability and impairment-related changes in subjects' motor strategies. RESULTS: The parameters derived from the model effectively differentiated between motor strategies associated with different performance-based scores, and allowed the identification of relevant difficulties encountered in STS execution. These difficulties could be associated with different strength scores. This was also true for subjects scoring the maximum in both performance-based and strength tests. CONCLUSIONS: The MMIM is a relatively inexpensive and noninvasive approach that enhances mobility assessment of hemiparetic subjects with different motor ability levels. It provides information that correlates well with performance-based and strength scores and, in addition, it allows for subject-specific motor strategy identification.

Aged↗

PubMed2005

Sequencing sit-to-stand and upright posture for mobility limitation assessment: determination of the timing of the task phases from force platform data.

The identification of quantitative tools to assess an individual's mobility limitation is a complex and challenging task. Several motor tasks have been designated as potential indicators of mobility limitation. In this study, a multiple motor task obtained by sequencing sit-to-stand and upright posture was used. Algorithms based on data obtained exclusively from a single force platform were developed to detect the timing of the motor task phases (sit-to-stand, preparation to the upright posture and upright posture). To test these algorithms, an experimental protocol inducing predictable changes in the acquired signals was designed. Twenty-two young, able-bodied subjects performed the task in four different conditions: self-selected natural and high speed with feet kept together, and self-selected natural and high speed with feet pelvis-width apart. The proposed algorithms effectively detected the timing of the task phases, the duration of which was sensitive to the four different experimental conditions. As expected, the duration of the sit-to-stand was sensitive to the speed of the task and not to the foot position, while the duration of the preparation to the upright posture was sensitive to foot position but not to speed. In addition to providing a simple and effective description of the execution of the motor task, the correct timing of the studied multiple task could facilitate the accurate determination of variables descriptive of the single isolated phases, allowing for a more thorough description of the motor task and therefore could contribute to the development of effective quantitative functional evaluation tests.

Adult↗

PubMed2004

Total body centre of mass displacement estimated using ground reactions during transitory motor tasks: application to step ascent.

A double integration technique is presented that estimates whole body centre of mass (CoM) displacement from signals of a single force platform, compensating for the drift and low frequency noise inherent in the signals. The technique is composed of two different integration techniques, which may also be used separately, and is applied to transitory motor tasks with known initial and final conditions such as step ascent and descent, single step, etc. First, the lowest frequencies within the force platform signals and considered not to be associated with actual movement are filtered out. Second, a regular and a time-reversed double integration are performed and weighted against each other. The technique's accuracy was assessed using computer generated force platform signals that were artificially perturbed. Experimental data were used to compare the estimated CoM displacement to that obtained from a regular double integration and from segmental analysis performed on stereophotogrammetric data. It was shown that the proposed technique's CoM displacement estimates were more repeatable and up to 50% more accurate than those of a regular double integration. Moreover, the CoM displacement estimated using a single force platform and the proposed technique was found to be not statistically different from that obtained with more demanding measurement and processing techniques such as stereophotogrammetry and segmental analysis.

Adult↗

PubMed2004

An optimization algorithm for human joint angle time-history generation using external force data.

A mathematical model is presented that estimates joint kinematics and kinetics using measured external resultant loads and readily available parameters. The musculo-skeletal system was represented by a planar three degrees of freedom open kinematic chain. Information extraction was limited to the flexion-extension function of ankle, knee, and hip during quasi-planar motor tasks. Starting from plausible first approximation kinematics, other kinematic functions are iteratively generated by an optimization algorithm and corresponding ground reaction loads are calculated through inverse dynamics. Kinematic coordinates are represented using B-splines and modified by manipulating the control points. The iterative procedure stops and provides the final kinematic and kinetic estimates when a similarity criterion between estimated and measured ground reaction components is satisfied. The model structure was elaborated upon and the algorithm parameters optimized for robustness and accuracy using a benchmark motion in a simulation exercise. The maximal root mean square difference over time between estimated and benchmark quantities was approximately 1% of the peak to peak value for ground reaction components and intersegmental couples, and 6% for joint angles.

Algorithms↗

PubMed2004

Association between subject functional status, seat height, and movement strategy in sit-to-stand performance.

OBJECTIVES: To explore the association between an individual's functional status, movement task difficulty, and effectiveness of compensatory movement strategies within a sit-to-stand (STS) paradigm. DESIGN: Cross-sectional study. SETTINGS: Rehabilitation unit of the Istituto Nazionale Riposo e Cura Anziani Geriatric Hospital of Florence, Italy. PARTICIPANTS: A convenience sample (131 subjects) of the outpatient clinic and day-hospital population. MEASUREMENTS: A performance-based test (repeated chair standing) was used to divide the subjects into five functional groups. Subjects performed a series of single STS tasks across a range of five descending seat heights. They were instructed to stand without using arms or compensatory strategies. If unable, swinging the arms was allowed, and if the inability persisted, subjects could push with their arms during subsequent attempts. The strategy or inability to stand formed the dependent measures. RESULTS: Subjects within the two highest functional groups could complete the single STS task at all seat heights, with a slight increased use of compensatory strategies at the lowest seat height. The effectiveness of the compensatory strategies decreased rapidly as a function of seat height and functional status. One-third (35.5%) of the subjects in the middle functional group swung their arms at the lower seat heights. Across the three least functional groups, 11.8%, 30.6%, and 83.3% of the subjects, respectively, were unable to stand at the lowest seat height. CONCLUSION: The individual's functional status and difficulty of the task influenced the effectiveness of a compensatory strategy to maintain the ability to stand, supporting the idea that disability depends on the interplay between environmental demands and physical ability.

Aged↗