How do you learn to walk? Thousands of steps and dozens of falls per day.

A century of research on the development of walking has examined periodic gait over a straight, uniform path. The current study provides the first corpus of natural infant locomotion derived from spontaneous activity during free play. Locomotor experience was immense: Twelve- to 19-month-olds averaged 2,368 steps and 17 falls per hour. Novice walkers traveled farther faster than expert crawlers, but had comparable fall rates, which suggests that increased efficiency without increased cost motivates expert crawlers to transition to walking. After walking onset, natural locomotion improved dramatically: Infants took more steps, traveled farther distances, and fell less. Walking was distributed in short bouts with variable paths--frequently too short or irregular to qualify as periodic gait. Nonetheless, measures of periodic gait and of natural locomotion were correlated, which indicates that better walkers spontaneously walk more and fall less. Immense amounts of time-distributed, variable practice constitute the natural practice regimen for learning to walk.

Baby carriage: infants walking with loads.

Maintaining balance is a central problem for new walkers. To examine how infants cope with the additional balance control problems induced by load carriage, 14-month-olds were loaded with 15% of their body weight in shoulder-packs. Both symmetrical and asymmetrical loads disrupted alternating gait patterns and caused less mature footfall patterns. Walking was most severely compromised by back loads. Infants with less walking experience, lower levels of walking proficiency, and chubbier body proportions were more adversely affected. In addition, infants displayed a unique postural response to asymmetrical loads. In contrast to older children and adults, infants leaned with loads rather than in the opposite direction to the loads. Findings are discussed in terms of development from accommodation to compensatory strategies.