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Physiological and psychophysical comparison between a lifting task with identical weight but different coupling
Kent J Adams1, Mark DeBeliso, Patricia G Sevene-Adams
1Exercise Physiology Lab, Kinesiology Department, California State University Monterey Bay, Seaside, California, USA. kadams@csumb.edu
Journal of Strength and Conditioning Research
|January 15, 2010
Summary
This study found that good grip quality (coupling) increased physiological and perceived stress during lifting tasks, contrary to the National Institute for Occupational Safety and Health (NIOSH) lifting equation's theory. These findings challenge assumptions about lifting stress and injury prevention.
Area of Science:
- Occupational Health
- Ergonomics
- Biomechanics
Background:
- The revised National Institute for Occupational Safety and Health (NIOSH) lifting equation aims to prevent lifting-related injuries.
- The coupling component, assessing hand-to-object interface quality, is theorized to influence lifting stress.
- Good coupling is expected to reduce, while poor coupling is expected to increase, lifting stress.
Purpose of the Study:
- To compare physiological and psychophysical stress during a lifting task with identical weight but varying coupling factors.
- To investigate the relationship between grip quality and the metabolic and perceived exertion during manual handling.
Main Methods:
- Twenty-one healthy adults performed a paced, 5-minute lifting task involving transferring a 12.5 kg load between floor and table.
- Two distinct objects with different coupling qualities (milk crate vs. bag of dog food) were used.
- Steady-state metabolic data (oxygen consumption, caloric cost, heart rate, respiratory exchange ratio) and rating of perceived exertion were collected.
Main Results:
- Lifting with a milk crate (good coupling) resulted in significantly higher oxygen consumption, caloric cost, heart rate, and rating of perceived exertion compared to lifting a bag of dog food (poor coupling).
- No significant difference was found in the respiratory exchange ratio between the two lifting conditions.
- These results indicate increased physiological and psychophysical stress with better grip quality.
Conclusions:
- Contrary to theoretical expectations, a good quality grip (good coupling) led to higher metabolic costs and perceived exertion than a poor quality grip.
- The findings challenge the current understanding of how coupling affects lifting stress within the NIOSH lifting equation.
- These results may inform workplace practitioners in designing and pacing lifting tasks for improved injury prevention and productivity.
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