Classes include Yoga, Pilates, fitness training etc.
Exact times and dates are published in the leaflet "Freizeitsport Sommer 2006" - available at the Stadtinformation in the town hall or online: www.sport-muenchen.de.
It's in German, click "Veranstaltungskalender und Aktuelles", then "Freizeitsport", "Sommerprogramm 2006" and "Park-Gymnastik".
I hope this info is useful for some of you.