Subjective evaluation of low load muscle fatigue at shoulder

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Subjective evaluation of low load muscle fatigue at shoulder

 

Author: To, Tze-shing
Title: Subjective evaluation of low load muscle fatigue at shoulder
Degree: M.Sc.
Year: 2000
Subject: Shoulder
Muscles -- Physiology
Fatigue
Loading and unloading
Hong Kong Polytechnic University -- Dissertations
Department: Multi-disciplinary Studies
Dept. of Rehabilitation Sciences
Pages: ix, 76 leaves : ill. ; 30 cm
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b1541810
URI: http://theses.lib.polyu.edu.hk/handle/200/2792
Abstract: This study aimed to explore the relationship between the amount of load, loading time, and perceived muscle fatigue in a low-level static-loading situation. The intensity of muscle fatigue was measured by a visual analog scale (VAS). Twenty-five healthy female subjects, aged 28.4 years (SD=4.3) were recruited to participate in the laboratory-based testing. There were ten loading protocols with a cross design of five loads (0 to 20% maximum voluntary contraction) and 2 loading times (1 and 2 minutes). Protocols were randomly sequenced and presented to subjects. Subjects' dominant upper arm was positioned at a 30-degree of shoulder flexion and the load was applied as per the protocol. They were asked to report their fatigue sensation at the shoulder on the VAS scale immediately after each of the protocols. The results revealed largely moderate correlations between subjects' fatigue and the amount of load (r ranged from 0.62 to 0.63) and loading time (r between 0.53 and 0.57). Both variables accounted for about 50% of the variance of the fatigue of subjects. Subjects' fatigue at the shoulder significantly increased across the five different loads and two different loading times. Our findings reveal a linear relationship between the fatigue experienced by the subjects, and the amount and time of the static load applied to them. These observations were supported by the increased oxygen consumption and decreased circulation within the muscle as the result of muscle exertion and sustained contraction. This pattern was found to be similar to those revealed for the high-level loading situation. It may suggest the notion that the fatigue phenomenon shares a similar model in both the low and high level load situation. Our results further support the validity and sensitivity of using VAS in measuring fatigue in a low-level static load. The load and loading time used may be useful parameters for future study on developing a comprehensive model for the evaluation of low load exposure such as in VDT work. The understanding of their effects could facilitate the development of guidelines for alleviation of workers' fatigue and thus enhance occupational health at the workplace.

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