I expect the total force required to turn depends also on the vehicle's weight, degree of turn, etc. My manual, 90's Japanese sedan (approximately 3,000 lbs iirc) stalled on me while I was exiting a freeway at ~30mph, along a round, ~270° turn. My first instinct was to try put the car back into gear, but before I could effectively do that, I realized I needed both hands on the wheel just to wrestle the car through the turn. I could have easily caused an accident. The disorientation of losing power steering while turning, and having to move my right hand from shifter to wheel made this a serious situation. If my car were heavier, or the turn were tighter, or if I reacted slower, (all of which are more likely than a very serious muscle weakness), it could have been much worse.