Matintalo, who starts for the Pöytyän Urheilijat, made its first international appearance at the European Youth Olympic Winter Festival 2013 in Predeal . There she was eighth over 5 km classic and fourth in the mixed relay. She made her debut in the cross-country skiing world cup in November 2014 in Ruka and achieved 70th place over 10 km classic. At the Nordic Junior World Ski Championships in 2015 in Almaty , she came in 29th place over 5 km freestyle, 16th place in the skiathlon and ninth place with the relay. In February 2015 she became the Finnish junior sprint champion. At the beginning of the 2015/16 season, she started in Vuokatti for the first time in the Scandinavian Cup . There she finished 62nd place over 10 km freestyle and 39th place over 10 km classic. Her best results at the Nordic Junior World Ski Championships 2016 in Rasnov were ninth place with the relay and fourth place over 5 km classic. At the U23 World Championships in 2017 in Soldier Hollow , she won the silver medal in skiathlon. In addition, she achieved 22nd place in the 10 km freestyle and 11th place in the sprint. In February 2017 she got her first World Cup points in Otepää with the 12th place over 10 km classic. At the Nordic World Ski Championships in Lahti in 2017 , she came in 29th place in the skiathlon. In March 2017 she became the Finnish junior champion over 5 km classic. In the 2017/18 season she took 50th place in the Ruka Triple and 30th place in the World Cup final in Falun . In addition, she took two wins in the Scandinavian Cup and thus reached ninth place in the overall standings. At the 2018 Winter Olympics in Pyeongchang , she finished 24th in the skiathlon, 19th in the sprint and 18th in the 30 km mass start race.
In the 2018/19 season, Matintalo finished 43rd in the Lillehammer Triple and achieved their first podium finish in the World Cup in Beitostølen with third place in the relay. At the season highlight, the 2019 World Championships in Seefeld in Tirol , she ran 32nd place in the skiathlon and 17th place over 10 km classic. The following season she took 35th place in the Ruka Triple and second place with the relay in Lahti.