When I did my interviews, it was understood that "strongly encouraged" was equivalent to "required". At two places I interviewed there was a resident at each who did not do research and was essentially ostracized by fellow residents and attendings--who said that choosing not to do research resulted in miserable remaining residency years, and that they were almost "forced out" of the program due to the choice.
If you are unsure about doing research, ask the residents when you interview how many people do research and if the answer is "everybody", if anyone has ever chosen not to do research and what was the program's reaction to this choice. This way at least you have an idea of what to expect should you match there.