Muscle Fatigue during Isometric and Dynamic Efforts in Shoulder Abduction and Torso Extension: Age Effects and Alternative Electromyographic Measures

Aging has been associated with numerous changes in the neuromuscular system. Age effects on muscular performance, however, have been addressed only in limited contexts in earlier research. The present work was conducted primarily to investigate age-related effects on muscle capacity (fatigue and endurance) during isometric and dynamic efforts. This work was also motivated by current theories on muscle fatigue as a potential risk factor for musculoskeletal disorders and recent demographic projections indicating a substantial increase of older adults in the working population. Four main experiments were conducted to investigate development of muscle fatigue during isometric and intermittent efforts in shoulder abduction and torso extension at different contraction levels. Two age groups were involved (n=24 in each), representing the beginning and end of working life. Findings from this study demonstrated that the older group exhibited slower progressions of fatigue, though the age effect was more consistent for the shoulder than the torso muscles. This implied a muscle dependency of the influence of age on fatigue. Several interaction effects of age and effort level were also observed, suggesting that both task and individual factors should be considered simultaneously in job design. The present investigation also sought to develop alternative electromyography (EMG)-based fatigue parameters for low-level isometric and dynamic contractions, two areas in which improvements are needed in the sensitivity and reliability of existing EMG indices. Several alternative EMG indices were introduced, derived from logarithmic transformation of EMG power spectra, fractal analysis, and parameter estimation based on a Poisson distribution. Potential utility of several of these alternative measures was demonstrated for assessment of muscle fatigue.

Name thesis:degree_name

Ph. D.

Level thesis:degree_level

doctoral

Discipline thesis:degree_discipline

Industrial and Systems Engineering

Department dc:contributor.department

Industrial and Systems Engineering

Grantor dc:publisher

Virginia Tech

Year dc:date.issued

2005

Author dc:creator

• Yassierli, Yassierli

Chair dc:contributor.committeechair

• Nussbaum, Maury A.

Committee members dc:contributor.committeemember

• Madigan, Michael L.
• Lockhart, Thurmon E.
• Babski-Reeves, Kari L.

• Aging
• electromyography
• fractal
• muscle fatigue

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Dc Identifier Other

etd-11092005-150452

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/29509