The effect of speed variation on initial and sustaned forces during pushing and pulling activities: a preliminary study

Push and pull activities characterize a significant part of manual material handling tasks in industry. Epidemiological studies show that pushing and pulling activities are associated with shoulder and low back pain. The International Standard 11228-2 describes the approach for risk assessment of push/pull activities, providing the maximum acceptable initial and sus-tained forces for pushing and pulling. The Standard defines maximum acceptable forces, re-quiring not to push/pull faster than a prescribed speed limit (0.1m/s for initial force and 0.3m/s for sustained force). Previous studies and current practice show that workers push carts faster. The purpose of this study was to evaluate the relationships between speed variation and push forces for pushing tasks in industry. An industrial cart was pushed at different speed val-ues. Maximum initial and sustained push forces were measured. Results showed that increas-ing speed was highly correlated to increasing push forces. The findings have practical value for researchers, occupational physicians and ergonomics practitioners.