Does reduced hamstring flexibility affect trunk and pelvic movement strategies during manual handling?

Objective: To evaluate the influence of reduced hamstring flexibility on trunk and pelvic movement strategies adopted by healthy males during manual handling tasks. Methods: Seventeen subjects performed a sagittally symmetrical handling task involving a 15 kg box, and hamstring flexibility was measured by means of the Straight Leg Raise Test. The task was filmed with a 2D acquisition system at a sampling rate of 50 frames/s. The images were digitized and a MatLab^® routine was implemented to analyze the trunk and pelvis movement patterns. Kinematic data from trunk movements were plotted against the data from pelvic movements in order to provide coordination analysis. Results: Subjects with reduced flexibility presented higher trunk movement amplitudes and a restriction on pelvis movements during handling tasks. Movement coordination was also influenced by the reduced flexibility. Conclusion: The results suggest that reduced hamstring flexibility is related to increased trunk angles, which can overload the spine during manual materials handling. Relevance to industry: Hamstring shortness can influence pelvic dynamics and, consequently, affects trunk movements adopted by subjects during occupational activities. As movement restrictions can reduce the capacity to obtain appropriate postural responses, this should be accounted for in order to provide better comprehension on how to prevent low back injuries in the occupational setting.