Lehtonen was born in Tampere, Finland in 1968. Always interested in outdoor activities, she joined a sports club in 1983 and became a track athlete. Through training as a sprinter she discovered an interest in weightlifting. After two years of growing interest in bodybuilding, she decided to see if she could compete in the field and entered the Finland National Championship. She won 2nd place in the lightweight category, taking her to the World Championship in Mexico City in 1990, where she finished 7th.
Lehtonen stands 5’2″ and competes at a weight of 120 pounds (her off-season weight is 138 pounds). As a teenager she competed as a sprinter before turning to bodybuilding.