Sundkvist has won six consecutive Finnish championships in the High jump at the senior level. Her record has been 1.87 m since 1976. Sundkvist has improved the Finnish record six times from 1974 to 1976 (from 1.75 to 1.87 m). At club level she represented Idrottsföreningen Drott and Kokkola Veikko of Pietarsaar. She reached silver in the European Athletics U20 Championships in 1975 in Athens with a measure of 1.86 m. She was coached by Göran Brunell.
Sundkvist is the youngest winner of the Finnish high jump championship. The 1973 championship reached 15 years, 8 months and 2 days. It is also the youngest medal (14 years, 8 months, 4 days).