Marine veteran John Dunbar lost an arm and a leg in a motorcycle accident six years ago, but that hasn’t stopped him from being active. With the help of prosthetics and specialized sports equipment, the 35-year-old Springfield resident lifts weights, swims, cycles and paddles a kayak. Dunbar said he learned how much he could do while attending Veterans Affairs sports clinics. “It gave me the opportunity to figure out what type of adaptive equipment worked for me,” he said. “It’s definitely helped out a lot, gets you more in shape.” Dunbar was among the veterans who spoke Thursday at the …