Being trained and having experience are two very different things. From my days working on a factory assembly lines, I found that being on a new line--even after being thoroughly trained on that line and assumed proficient--was difficult. It took from several days to a couple of weeks of eight-hour days before the required movements and steps became second nature. Until then, I struggled to keep up, as was the case with everyone for a time when they first began on a new segment of the line.
