Constraints on early movement: tykes, togs, and technology.

Examining the effects of diapers and other external constraints on infants' leg movements may affect how we collect motor control research data, dress infants to allow optimal movement in the home, and administer therapeutic interventions for infants with motor impairments. To address this issue we supported 12 healthy infants (2-4 months) on an infant-sized treadmill in each of four conditions: wearing nothing (None), a swim diaper (Swim), a disposable diaper (Diaper), or a combination of diaper and research recording equipment (All). We recorded the trials with a digital video camera and behavior coded number of steps and step type (alternating, parallel, double, or single steps) to assess both quantity and quality of movements. Infants produced similar numbers of steps in a predominantly alternating step pattern (high quality) during the None, Swim and Diaper conditions, but both quantity and quality of stepping decreased in the All condition. Our results suggest that diapers alone do not alter stepping patterns significantly, but sufficient additional weight and clothing beyond the diaper can affect movement frequency and quality in young infants.