A tradition of Boston Marathon weekend that continues for its 38th year, the John Hancock Sports & Fitness Expo—packed with more than 200 vendors showcasing the latest athletic, health and running accessories and trends—returns once again to the Back Bay’s Hynes Convention Center (900 Boylston St.). Taking place April 17 from 2–7 p.m., April 18 from 9 a.m.–7 p.m. and April 19 from 9 a.m.–6 p.m., the expo doubles as the spot where Boston Marathon runners pick up their numbers, so there’s plenty of runners as well as nearly 100,000 other health aficionados in attendance. Visitors can also enjoy a popular series of seminars on choosing the right running gear, how to run your best and more, all hosted by Runner’s World magazine. And if all of this wasn’t enough, admittance is free. For more details, visit sportsfitnessexpo.com.