This thesis examines trajectory reconstruction during a drinking task, a common rehabilitation exercise used to assess upper limb functionality, using a single inertial unit (IMU) worn on the wrist. Compared to other human motion capture methods, inertial measurements are a cheaper and more ergonomic alternative, but they are prone to noise and drift errors that by accumulating over time, lead to an inaccurate estimation. The aim of this work is to develop an optimization-based method to enhance trajectory reconstruction accuracy when using a single wrist-mounted IMU within a structured protocol. The proposed method is validated against a stereophotogrammetric gold standard. This approach has potential applications in telerehabilitation by enabling objective clinical assessments of functional tasks with minimal setup, making it accessible for remote use by non-experts.