My husband, teenager son and I go to Formosa Fitness. It's an excellent gym, it has enough for a great workout and the trainers are very good. The price is very reasonable and is close (like 5 minutes walking distance) to Guting MRT Exit 8. They also have classes, Kettlebells, Strength Training and Olympic lifts I believe. I'm very pleased with the progress I made during my strength classes and really enjoying the one-on-one training as well. We attended recently a Strength Camp and is was very good. My son is in excellent physical condition and he felt challenge. My husband and I felt very challenged and learned a lot. It was wonderful.
I highly recommend Formosa Fitness and I'm convinced this is the best gym in Taipei.
Their physical address is
XiaMen St. Lane 25, #2, Taipei, Taiwan 106