STATUS IN HUMAN STRENGTH RESEARCH AND APPLICATION

Comparison of static lifting capacity between experienced and novice Taiwanese female workers

BACKGROUND

Previous studies have analyzed the lifting capacity of either experienced workers or novices, but a systematic comparison of the lifting capacity of experienced female workers and novices has not been conducted.

OBJECTIVE

This study was conducted to identify differences in lifting strengths and postures between experienced and novice Taiwanese female workers.

METHODS

Twenty-three experienced female workers and 23 novices volunteered for this study. Their static lifting strengths (n = 46) and lifting postures (n = 22) were analyzed using statistical analysis software.

RESULTS

Experienced workers' vertical lifting strengths were approximately 5-7  kg lower than those of novices at lower heights (≤50  cm). However, at heights equal to or higher than 90  cm, the experienced workers generated approximately 2-3  kg higher toward-body lifting strengths than did novices. The experienced workers' strengths at all 15 lifting heights were relatively unchanged, compared with changes in the novices' strengths. Experienced workers tended to adopt a consistently deep squat at lower heights and a more flexed arm posture at higher heights.

CONCLUSIONS

Through daily work experience, experienced workers may have subconsciously learned to shift their postures to avoid overexertion. These techniques for safe lifting should be taught to new Taiwanese female workers.

An isometric predictor for maximum acceptable weight of lift for Chinese men

The aim of this study was to examine the practicality of the modified isometric strength tests to predict the maximum acceptable weight of lift (MAWL) of Chinese men. The modified strength tests allow the participant to pull on the load cell in front of the body and to apply force in a functional free posture. Both the modified and the standard strength data of each participant were used as predictors for the MAWLs. The prediction models were constructed and evaluated under task conditions of two lifting ranges, two box sizes, and three lifting frequencies. To realize the effect of modifications, testing posture was recorded and the joint angles were calculated. A stepwise multiple regression analysis indicated that modified composite strength (MCS), chest circumference, and acromial height accounted for 86% to 91% of the variance. Because the strength of the upper extremity body was also recruited in the test, the weak upper extremity strength of the Chinese participants would therefore be better reflected. Evidence for the existence of a close match between MAWL and MCS values, as well as the task conditions for its existence, suggest that a simple isometric strength measure is a good predictor for the MAWL.