This type of exercise works whole body and improves conditioning and muscular endurance. Circuit training is done by performing one exercise after another set up at various stations. For example you might perform a set of squats followed by a set of upright rows followed by curls etc. The trainer will guide you through the exercises, often twice around the entire circuit, then you are free to continue as you wish. The FLEX part of the name means you can arrive anytime between the start time and the posted “last start” time at your convenience and join the rotation of the circuit!