Based on my experience, I can say that retro-walking takes more concentration than you'd think. Normally, when walking on my treadmill, my eyes can wander anywhere in my messy garage to pass the time.
She had a lot of discomfort at the time and was game to find any solution. Byrd started retro walking on the treadmill before workouts for five minutes at two miles per hour at a 5% incline.