elongate

1. V-T/V-I If you elongate something or if it elongates, you stretch it so that it becomes longer. (使)拉長; (使)延長[正式]

"Mom," she intoned, elongating the word. “媽媽，”她拖長了聲音，緩緩地說道。

In this exercise, the muscles are elongating rather than contracting. 在這項運動中，肌肉是在延伸而不是在收縮。