Biomedical subjects

Maury A Nussbaum

Publications and source records attributed to Maury A Nussbaum.

4 recordsLinked to original sources

PubMed2003

Principal components analysis as an evaluation and classification tool for lower torso sEMG data.

The use of univariate statistical techniques on multivariate electromyography data can fail to uncover important relationships between variables. Principal components analysis (PCA) is a multivariate statistical technique that can be used as a data exploration tool, both by classifying participants and simplifying data structures. Past research using this technique has focused on discriminating between "patients" and "normals". This investigation explored the use of PCA on electromyography data from healthy participants, with the objective of elucidating any between-participant differences in the multivariate patterns of muscle coactivation. Results indicated that, even between healthy participants, quantitative and qualitative differences in muscle coactivation patterns exist and that, in the context of the lower torso, a large portion (>70%) of the empirically determined muscle activation could be synthesized in a theoretical three-parameter control model.

Abdominal Muscles↗

PubMed2002

Lower torso muscle activation patterns for high-magnitude static exertions: gender differences and the effects of twisting.

STUDY DESIGN: Surface electromyographic signals were collected from 14 lower torso muscles while participants resisted high-magnitude static trunk moments applied in a variety of directions. OBJECTIVES: To obtain a description of muscle activations in response to large moment magnitudes and axial twisting, including levels of agonistic and antagonistic muscle cocontraction. To assess differences in lower torso muscle activation patterns associated with gender and trial repetition. SUMMARY OF BACKGROUND DATA: Back pain is associated with mechanical loads in the back. Biomechanical modeling of these loads is facilitated by knowledge of typical muscle activation patterns. Previous efforts in obtaining such data have often limited their scope to low-magnitude exertions or relatively simple scenarios. METHODS: Eight male and eight female participants, matched by height and mass, performed static exertions in an apparatus that immobilized their lower body while the activation levels of seven bilateral torso muscles were measured using surface electromyography. Activation patterns were analyzed to assess differences resulting from a variety of factors. RESULTS: No significant differences in activation patterns were found between genders or repetitions, but moment magnitude and direction elicited substantial differential responses. Good repeatability was found between trial repetitions, as indicated by intraclass correlation coefficients (>0.65). Significant synergistic muscle coactivation, large intersubject variability (mean coefficient of variation 82.2%), and consistent levels of antagonism ranging from 10% to 30% maximum voluntary exertions were observed. CONCLUSIONS: Individuals of different genders, but similar anthropometry, have comparable muscular reactions to complex torso loads, suggesting similar motor control strategies. Future spine models should consider that the variability in muscle recruitment patterns is larger between subjects than within subjects. High-magnitude exertions, especially those with moment loads in more than one plane, require most muscles to be active (>5%) and moderate levels of antagonism.

Adult↗

PubMed2002

Determination and evaluation of acceptable force limits in single-digit tasks.

Acceptable limits derived from psychophysical methodologies have been proposed, measured, and employed in a range of applications. There is little existing work, however, on such limits for single-digit exertions and relatively limited evidence on several fundamental issues related to data collection and processing of a sequence of self-regulated exertion levels. An experimental study was conducted using 14 male and 10 female participants (age range 18-31 years) from whom maximal voluntary exertions and maximal acceptable limits (MALs) were obtained using the index finger and thumb. Moderate to high levels of consistency were found for both measures between sessions separated by one day. Single MAL values, determined from a time series of exertions, were equivalent across three divergent processing methods and between values obtained from 5- and 25-min samples. A critical interpretation of these and earlier results supports continued use of acceptable limits but also suggests that they should be used with some caution and not equated with safe limits. This research can be applied toward future development of exertion limits based on perceived acceptability.

Adolescent↗

PubMedDate not supplied

Postural stability is compromised by fatiguing overhead work.

In a laboratory setting, 16 participants performed a repetitive overhead tapping task for 3 hours or until self-terminated due to substantial shoulder discomfort. Several measures of postural sway and stability were obtained using a force plate, both during quiet standing and during performance of the tapping task. Sway area and peak sway velocity showed consistent increases with time, whereas changes in average velocity and peak whole-body center-of-mass acceleration were either small or nonsignificant. Although relatively insensitive to several task variables, changes in sway areas and peak velocities were substantially larger in trials terminated by the participants. It is argued that fatigue plays a more important role than simple task duration in causing the observed increases in sway, and hence decreases in postural stability. Potential whole-body consequences of localized musculoskeletal stresses appear supported by the results, and implications for safety, risks of falls, and work scheduling are discussed.

Accidental Falls↗