Muscle activation levels in anterior trunk sway compared to posterior trunk sway. Muscle activation levels are presented as the relative change in EMG to the reference Upright Standing (hatched bars) as well as the mean of the individual differences in activation (diamonds). Positive difference values indicate higher activation levels for the given muscle in anterior trunk sway, negative values represent increased activation levels in posterior trunk sway. The values are the difference relative to the activation level in upright stance. For example, semitendinosus activation is higher (293% of the level in upright stance) in Anterior Trunk Sway compared to Posterior Trunk Sway, whereas rectus femoris is activated more (212%) in Posterior Sway compared to Anterior Sway. The 95% CI are represented by the whiskers. Semitendinosus (ST); biceps femoris (BF) (long head); gluteus maximus (Gmax); rectus femoris (RF); vastus lateralis (VL); tensor fascia lata (TFL); gluteus medius (Gmed); and adductor longus (AL).