a) What type of study is this?
b) Can this study be used to conclude a causal relationship between increased stress and muscle cramps?
The study creates stress in a way that might affect muscle cramps.
If an elevator falls rapidly and stops abruptly, that could affect muscle cramps more because of the physical action than by the stress it induced.
I don’t think this experiment would help answer whether there is a causal relationship between increases stress and muscle cramps.