I'm too embarrassed to learn

In teaching Muscle function, I have always used an activity where I physically demonstrate the actions to students. Students then stand and work in pairs, mimic the movements on their own body, and evaluate their partner's motions. I circulate and correct with each new motion. When doing the activity as a class, and only their partner is working with them, students think this activity is fun and interesting. The class is excited and loud. However, in the next section where they review with their lab group of 4, they are reluctant to continue the motions on their own, and seemed embarrassed by three people evaluating them. To overcome this issue, we ordered small wooden artists models of the human body that move at the joints. Students work in groups of two and make the models do the motions. I list a series of actions (arm abduction, neck flexion, knee extension), and the students must place the models in the correct position. There is much more interacation and interest in the assignment when they have this "toy" to play with. Quiz grades for muscle actions have gone up (to be posted).