There is still time to participate in the exercise groups in the park! Helsinki city offers a number of them for free and the last one I went to killed my thighs. There are also others that offer exercise in a park but then the prize varies from 2-3 euros to 7-8 euros. To all of this it is worth taking a water battle and a mat but you can just turn up and sweat with others, no signing up is required.
The next chance for you is to participate in the biggest outdoor yoga session in Koffari in Helsinki tomorrow at 6pm.