Female maximal push/pull strength capabilities by humeral abduction angle in bilateral exertions

Pushing or pulling an object constitutes the majority of manual materials handling tasks. Anthropometric differences between workers alter pushing and pulling strategies at fixed heights, potentially modifying exposures and causing overexertion. Capability normalized to arm posture rather than work height remains unknown, and the purpose of this research was to quantify maximal pushing and pulling strength and upper extremity joint moments using fixed humeral abduction angles and a flexed arm position. Twenty university-aged females completed maximal pushes and pulls at 0°, 30°, 60°, 90°, and 120° of humeral abduction with an elbow to 90°. Abduction angle was the largest modifier of both push and pull force generating capability (p < 0.01), with increasing abduction reducing force capability by up to 30%. While push exertions on average exceeded pulls by 17 N (p < 0.01), the difference is much smaller than previous reports. Ergonomists should consider humeral angle of the worker rather than work heights, as individuals working in increased abduction decreases capability and increases potential overexertion injury risk.