Interpreting Joint Kinetics during Fatiguing Lifting: Should We Focus on Changes in Joint Moments or Changes in Our Moment Generating Capacity?

Controvery exists as to how fatigue can influence lifting biomechanics. Lifters have decreased their range of motion (ROM) at the hip and knee [1] and increased their flexion ROM at the trunk [2], while other lifters have responded oppositely, where hip ROM was increased and trunk ROM decreased concurrent with a decrease in moment loading on the spine, as a function of time [3]. It remains clear that fatigue impacts biomechanics during repetitive lifting; however controversy remains regarding the specific role fatigue may play, and in particular, whether fatigue is more influential in altering the biomechanical demands of the lift or in altering ones capacity to continue performing the lifting task. This study investigated how the biomechanical demands of the lift changed as a function of time (fatigue) while currently measuring an index of moment generating capacity.