Matintalo was a talented skier from an early age; as a youth, her training programs for skiing and running were compatible and supported each other. She represented Finland in cross-country skiing at the 2013 European Youth Olympic Winter Festival in Brașov, placing eighth in the 5 km classical race. In 2015, she competed in the World Junior Championships in Almaty, where she placed 16th in the under-20 skiathlon.