Never heard of it with a treadmill cord. Venetian blinds are usually the cause.
I have a three year old granddaughter,,called her mom to take up all the blind cords and drapery cords,,it is horrible.
Yes, I actually saw a child in our Peds ICU who was in his crib next to the window, got the cord for the blinds around his neck, and had the same fate as this little girl.