I was working out on my approx 4 month old treadmill (NordicTrack model C1550) and had the track moving to an 8 incline at a 4.8 speed when the machine completely stalled. I had done a 3 min warm up at 4.8 speed/2 incline prior to increasing the incline to 8. Within 60 seconds of increasing the incline, the machine came to an abrupt halt. I jolted forward, with my upper torso falling into the control panel and my toe box on my right foot riding up slightly on the plastic piece covering the front of the track (which extends at least 3-4" farther than the control panel). Approximately 1-020 seconds after it abruptly stopped, the treadmill started up again at the 4.8 speed it was at prior to stalling and I fell to the track, literally coming within 2” of my face/front teeth going into the control panel. The track drug my feet back twisting my right ankle underneath my leg, with the top of my right foot sustaining an abrasion from the tread and my knee getting torn up and bruised prior to the machine emergency stopping when the red switch finally pulled out. My right knee and top of my right ankle were bleeding and my right ankle became very swollen. I also experienced significant bruising on my right knee, and whip-lash like symptoms with midback and neck pain.
My doctor diagnosed me with an ankle sprain, mid and upper back sprain and right knee abrasion and contusion.
As a side note, this treadmill is kept on a surge protector on it's own circuit. I also came across 5+ recent online NordicTrack treadmill reviews where users had similar experiences to what happen to me on 8/4, where the treadmill had abruptly stopped without warning.