Nietschmann, P.; Franklin, D. W.

Motor skills such as bicycle riding are considered robust and transferable across bicycle types. However, when the steering direction is inverted (reversed bicycle) control is disrupted to the extent that the bicycle cannot be ridden. With sufficient practice, the reversed bicycle can be learned, but this learning appears to produce impairment of normal bicycle riding suggesting modification of this long-established motor memory. Here we investigate the learning process of riding a reversed bicycle over four days of practice, while repeatedly assessing normal bicycle performance to measure any potential interference. Introduction of the reversed bicycle disrupted predictive control, reflected in a consistently increased time lag in the steering-roll coupling during reversed bicycle trials. This increase in delay suggests that predictive behavior in normal bicycle riding cannot be transferred to the reversed bicycle. With training, some participants successfully learned to ride the reversed bicycle by gradually reorganizing this coupling, whereas others failed to acquire this inverted coupling. Notably, even short-term exposure to the reversed bicycle interfered with normal bicycle riding, reducing distance ridden and increasing variability in steering rate. Together, we show that even a highly practiced whole-body motor skill is susceptible to rapid interference when control dynamics are altered.