There are always comfort zones. Experts experience them just as much as beginners.
Asking professional musicians to play a piece of music differently than they are used to, is asking them to expand their comfort zone. It might even feel more difficult for them than for others, as failing from their perspective means to fail at a larger scale. They’ll for example see that their reputation might be at stake.
It means that, independently from being a beginner or an expert, they all will react in the same way when they being asked to stretch themselves. They’ll start by fearing that it can’t be done. A place from which many will respond with an idea that it can’t be done.
The leader who created that stretch needs to hold on to it. It might not work out perfectly, but that’s not what the stretch is for. It is there to let the team experience its capacity to contribute and develop itself. The leader’s task is to be supportive in these moments. By watching how they find a way to deal with the stretch, they show their team that they trust them and that they see their potential to grow.
The satisfaction the team experiences comes from the disbelief at the beginning, the trust they receive, as well as the experience they make while seeing themselves achieve what they thought to be too difficult.
Not to forget, that the result is more than what had been possible before.
The reverse effect is achieved when protecting a team from being stretched. They’ll enter a cycle of achieving less.