Search for encyclopedia-length information on topics, sports, people. This is basic overview/background information from a large collection of encyclopedias online.
Books will be good options for those doing topics on people, broad topics like adventure therapy, and large outdoor organizations. Books will be less helpful for hot topics, narrow topics, and recent trends. Try articles for those topics.
I don't usually recommend this, but for this assignment, I think searching WorldCat will be helpful. Be sure to limit to books. Borrow items we don't have on InterLibrary Loan.
Professional organizations frequently offer industry research, trends, evaluation, and other useful info.
You can get really specific with different activities. There's an organization for all sporting goods and for specific sports. Here are a few examples. Look for others by googling your activity and either 'professional organization' or 'industry association'.