He was the eldest of the successful Finnish runners, the others being Lasse Virén, Pekka Vasala, Tapio Kantanen, Martti Vainio, and Kaarlo Maaninka, who came into the limelight in the 1970s.

[2] In 1965-67, his main event was the 800 metres, in which he won Nordic Championship in 1965, beating, for example, young Anders Gärderud.

[6] He was also interested in altitude training as early as the winter of 1966-67, when he spent seven months in Alamosa as a student.

On his return to Finland, he ran the 3000 metres in Helsinki in 8:01.0, improving his personal best by 52 seconds.

However, he was not able to compete because of an infection he received from a drug injection due to his weak blood test results.

As his original intention was to continue training in Brazil after the race, he decided to stay in Penedo, Itatiaia.

[citation needed] In front of a highly excited Finnish crowd, Väätäinen was in a group of six runners at the final bell following David Bedford, who had led from the start.

Väätäinen and Jürgen Haase both kicked past Bedford in a thrilling last lap "burn-up", bringing the crowd to its feet as they battled neck and neck to the line, with Väätainen just edging out Haase in a new Finnish record time of 27:52.78.

Väätäinen won this event as well, beating Jean Wadoux and Harald Norpoth in a new Finnish record time of 13:32.8.

On the following day, he ran 13:35.4 in Helsinki, placing third in the same race that Lasse Virén set a new world record, clocking 13:16.4.

Väätäinen served as a head coach of long-distance runners at the Finnish Athletics Association in 1988-90.