skeptical

adjective [原级]不相信的，持怀疑态度的；（哲）怀疑论的，不可知论的

If you're still skeptical about exercising, we can only ask you to trust us and give it a try. ^{如果你仍对锻炼持怀疑态度，我们只能请你相信我们，试一试。}