Getting in your sets of squats while standing on a balance trainer is one way to change up a stale leg day routine. A study published in the Journal of Strength and Conditioning Research take this practice to another level by adding an unstable barbell to the mix and testing it against lower body instability and traditional squats.
Wired to record activity in various muscle groups, 10 male volunteers performed squats while standing on a balance trainer, using a water-filled barbell and with a traditional barbell. Upper body instability reduced erector spinae muscle activation 1.5 times and increased abdominal activation 2.8 times compared to traditional squats. Lower body instability increased muscle activity in the gastrocnemius, biceps femoris, and quadriceps muscles.