The practice of monitoring training load in football and field hockey has become common. However, there is a lack of methods to quantify the biomechanical loads during training and competition. New methods to quantify biomechanical loads may help players, coaches, and medical staff to achieve an adequate balance between load and recovery to decrease injury risk and improve performance. By measuring lower body kinematics with inertial measurement units (IMUs), estimates of the biomechanical loads in football and field hockey may be obtained. In addition, neuromuscular fatigue is reported to be a major risk factor in some injuries, and quantifying fatigue-related changes in movement kinematics could perhaps be used in real-time injury risk monitoring. This thesis explores the potential of IMU-based motion analysis systems for biomechanical load quantification, and the quantification of the effects of football-specific neuromuscular fatigue on sprinting kinematics.