Abstract: A method and apparatus for monitoring musculoskeletal performance. A person repeatedly performing a physical task is monitored using a sensor system to generate task performance data. A simulation of the person performing the physical task over a number of cycles is run using a musculoskeletal model for the person and at least one of the task performance data and task description data. Muscle activation data and tendon force data are generated based on the simulation. Muscle fatigue and tendon fatigue resulting from performing the physical task are simulated for each cycle using a fatigue model system, the muscle activation data, and the tendon force data. The musculoskeletal model is adjusted to account for the muscle fatigue and the tendon fatigue after each cycle and prior to a next cycle. A prediction is made as to when a predetermined risk threshold for the person is reached based on the simulation.