Muscular fatigue and endurance during intermittent static efforts: effects of contraction level, duty cycle, and cycle time.

Full Abstract

OBJECTIVE:
To determine the effects of intermittent task parameters on muscle fatigue and endurance time during static shoulder abductions, with a long-term goal of establishing relationships between intermittent task parameters and short-term performance.

BACKGROUND:
Effects of intermittent work on endurance and fatigue development have been reported, and certain combinations of contraction levels and duty cycles have been proposed as design guidelines. These findings, however, were not derived from systematic manipulations of the task parameters.

METHOD:
Prolonged (1-hr maximum) intermittent shoulder abductions were performed at different combinations of contraction level (12% or 28% of muscle strength), duty cycle (.25 or .75), and cycle time (34 or 166 s). Fatigue was measured based on reductions in muscle strength and indirectly by changes in ratings of discomfort, electromyographic (EMG) amplitude, and EMG spectral distribution.

RESULTS:
Contraction level and duty cycle significantly affected endurance time and muscle fatigue, and interactive effects between these parameters were observed for some of the measures. Significant effects of cycle time were found only for EMG spectral measures.

CONCLUSION:
Endurance time and local fatigue were dependent on the comprehensive effects of the different task parameters.

APPLICATION:
Design changes to reduce the occurrence of localized fatigue during intermittent work need to take into account all the task parameters simultaneously.

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Author information

Author/s: Iridiastadi, Hardianto (H); Nussbaum, Maury A (MA);

Affiliation: Virginia Tech, Blacksburg, VA 24061, USA.

Journal and publication information

Publication Type: Comparative Study; Evaluation Studies; Journal Article

Journal: Human factors (Hum Factors), published in United States. (Language: eng)

Reference: 2006-; vol 48 (issue 4) : pp 710-20

Dates: Created 2007/01/23; Completed 2007/03/29;

PMID: 17240719, status: MEDLINE (last retrieval date: 12/26/2008)

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MeSH headings (categories)

This article was linked to the MESH Headings shown below.

Adult
Biomechanics
Electromyography
Female
Humans
Male

Muscle Contraction - physiology
Muscle Fatigue - physiology
Physical Endurance
Shoulder - physiology
Task Performance and Analysis
Time Factors

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