Influence of sagittal plane trunk posture on lower extremity biomechanics during running

摘要

Running is a popular form of exercise. However, a high incidence of lower extremity injuries has been reported in this population (19%--79%), with half of the diagnoses occurring at the knee joint. Sagittal plane trunk posture has been shown to influence lower extremity biomechanics during weightbearing activities. This suggests that trunk posture may be associated with knee biomechanics during running. Furthermore, diminished hip extensor strength has been suggested to affect trunk posture during weightbearing activities and may lead to an over-reliance of the knee extensors. The overall purpose of this dissertation was to examine the associations among sagittal plane trunk posture, lower extremity biomechanics and hip extensor strength during running. To achieve this goal, 3 studies were undertaken. The purpose of Chapter III was to examine the influence of sagittal plane trunk posture on lower extremity energetics during running. Results revealed that a more upright trunk posture was associated with higher energy absorption and generation of the knee extensors and lower energy generation of the hip extensors. The purpose of Chapter IV was to evaluate the association between sagittal plane trunk posture and patellofemoral joint (PFJ) stress and to determine whether modifying sagittal plane trunk posture influences PFJ kinetics during running. Findings revealed that an individual's self-selected trunk flexion angle was inversely correlated with peak PFJ stress. Additionally, a small increase in forward trunk lean was found to significantly reduce peak PFJ stress. The purpose of Chapter V was to examine the associations among hip extensor muscle strength, sagittal plane trunk posture and hip and knee extensor work during running. Findings revealed that hip extensor strength was positively correlated with trunk flexion angle and hip extensor work, and inversely correlated with knee extensor work. Taken together, the findings of this dissertation reveal that sagittal plane trunk posture has a significant influence on the mechanical demands of the hip and knee extensors during running. Furthermore, incorporation of a forward trunk lean during running may be an effective strategy to reduce loading at the knee. Lastly, diminished hip extensor strength may underlie the tendency of individuals to exhibit a more upright trunk posture and higher knee extensor work during running.