The Rotary Club of Westborough will host its fourth annual sprint triathlon next Sunday, and is seeking volunteers to help with various tasks from 7 to 10:30 a.m. The competition begins at 8 a.m. with a quarter-mile swim in Lake Chauncy, followed by a 14-mile bike ride and a 3-mile run. There will also be an off-road bike route, and a “splash-and-dash’’ race that skips the bicycle segment. A clinic will offer tips for triathlon beginners on Saturday. Organizers said they anticipate upward of 400 athletes taking part this year, and said they need all the assistance they can get. To sign up to volunteer, contact Jim O’Connor at 508-868-4309 or firstname.lastname@example.org. Registration to participate in any of the day’s events continues online until Friday, and can be arranged through on a link on the Rotary Club’s website, www.westboroughrotary.org. Proceeds will benefit the Rotary Club and the American Diabetes Association.