Balance Trainer Core & CardioAdd the TRNR Balance Trainer to your training arsenal for a workout that is guaranteed to challenge you. This versatile piece of equipment can be used for core training, balance, whole body strengthening, flexibility, and cardio. With a reversible design, it lets you vary the level of instability and mix up your routine for added motivation. For even more exercises targeting your upper body, you can purchase TRNR Strength Tubes X (from 3. 4 kg up to