In addition, the authors notice that walking took place in short bouts. That is, most of the bursts of activity consisted of one to three steps, which cannot be considered as periodic gait. These short bouts of walking are probably more efficient than massed walking. Indeed, motor memory is stronger and less susceptible to interference when learned in small periods of practice than during one extended period of practice (Kantak et al. 2010).
This paper elegantly demonstrates that the balance between cost and reward plays a key role in adopting new behaviors in natural situations as in laboratory settings.
Adolph, K. E. et al. How Do You Learn to Walk? Thousands of Steps and Dozens of Falls per Day. Psychological science 23, 1387–1394 (2012). doi:10.1177/0956797612446346
Todorov, E. & Jordan, M. I. Optimal feedback control as a theory of motor coordination. Nature neuroscience 5, 1226–35 (2002). doi:10.1038/nn963
Kantak, S. S., Sullivan, K. J., Fisher, B. E., Knowlton, B. J. & Winstein, C. J. Neural substrates of motor memory consolidation depend on practice structure. Nature Neuroscience 11–13 (2010).doi:10.1038/nn.2596