In my experience, 30-day fitness challenges can totally work for a wide range of people. I designed a challenge for our corporate wellness clients to see how many days in a month you can do at least 30 minutes of any physical activity. The results are pretty amazing. My wife personally prefers a Brazilian butt challenge. Here is a detailed review - https://verv.com/how-to-get-a-rounded-tush-with-the-brazilian-butt-challenge/