"受过严格训练的人" can be translated into English as "a person who has undergone rigorous training" or simply "a rigorously trained person".
Both expressions convey the idea that the individual has received thorough and disciplined training. Here are some examples in context:
He is a rigorously trained professional who excels in his field.
（他是一位受过严格训练的专业人士，在自己的领域表现出色。）
The team consists of highly skilled and rigorously trained athletes.
（这支队伍由技术高超且受过严格训练的运动员组成。）