Employees were installing trusses in a commercial construction setting. An employee was using standard pine studs as a catwalk to gain access between the newly installed trusses. One of the studs had a large defect (knot). When the employee placed his weight on the defective board, it broke. He fell approximately 22" to the concrete surface below, suffering blunt force trauma, head trauma, and severe bodily injuries. He was hospitalized. Fall protection was not worn at the time of the incident.