Jenben, I live in St Sulpice too and do that run to morges and back several times a week. there are also great runs up the venoge creek. there is a fitness center nearby in Denges, which is a little village between st sulpice and Preverenges to the north.

Harmony
Espaces de sport et bien-être
Les Marais
1026 Denges
www.harmony.ch
you can try it for free to see if it suits. there's yoga, pilates, bodysculpting, a pool, etc and it is not a "meat market." I don't belong, because I can't stand fitness centers, but I have several friends who really like it.

There is also a "gymnastics - stretching" class on thursday nights in the foyer paroissal in St Sulpice for women. good luck!