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Bilateral coordination in human infants: stepping on a split-belt treadmill
E Thelen1, B D Ulrich, D Niles
1Department of Psychology, Indiana University, Bloomington 47405.
Insights
Motorized treadmills stimulate infant stepping. Even with different speeds for each leg, infants coordinate steps, showing limb cooperation before voluntary walking.
Area of Science:
- Infant motor development
- Locomotion
- Biomechanical analysis
Background:
- Seven-month-old infants typically exhibit limited voluntary stepping.
- Motorized treadmills can induce stepping-like movements in infants.
Purpose of the Study:
- To investigate infant stepping responses to varying treadmill speeds.
- To examine interlimb coordination in infants before voluntary locomotion.
Main Methods:
- Infants were placed on a motorized treadmill with separate belts for each leg.
- Treadmill belt speeds were varied to assess step cycle duration and limb dynamics.
Main Results:
- Step cycle duration was dependent on treadmill speed.
- Infants adjusted stance duration on each belt to maintain alternating steps when belt speeds differed.
- Limb movements demonstrated cooperative behavior, with one limb's dynamics influencing the other.
Conclusions:
- Infant stepping on treadmills shows speed-dependent characteristics.
- Pre-locomotor infants exhibit coordinated limb movements, indicating anticipatory motor control.
- Interlimb coordination is present even before the onset of voluntary locomotion.
Abstract:
A motorized treadmill often elicits locomotor-like alternate stepping in 7-month-old infants who normally perform few, if any, stepping movements. The step cycle duration is a function of the speed of the treadmill. When infants were held so that each leg was on a separate treadmill belt, each of which was driven at a different speed, the overall cycle duration was intermediate between the cycle durations at the fast or slow speeds alone. Infants shortened the stance on the slow belt and increased the stance on the fast belt to maintain regularly alternating steps. Even before voluntary locomotion, both legs acted in a cooperative manner, with the dynamic status of one limb affecting the timespace behavior of the opposite limb.