Developing a rehabilitation intervention difficulty index: A mixed-methods study using NASA-TLX and Borg RPE in a tertiary clinical setting - Yazeed Temraz; Theeb Al Salem; Yousef Al Nufaie; Abdullah Aaltaza; Muhanna Almandoor; Turkey Al-Subaie; Sama Alshalawi; Saud Alsaadoon; Abdulrahman Al Hussein; Mohammed Aldakhil (PLoS ONE, 2026)