Additional weight influences the reaching behavior of low-risk preterm infants

The authors investigated the influence of additional weight in the reaching behavior of preterm infants. Nine low-risk preterm and 10 full-term infants age 5-7 months participated. A toy was presented in two procedures: (a) baseline and (b) additional weight (bracelet with weight of 20% of the infant's upper limb mass). The additional weight reduced the straightness index at 5 months, increased the mean velocity and decreased the movement units at all months, and increased unsuccessful grasps at 5 and 7 months in preterm infants. Preterm infants showed less movement units at all months and less unsuccessful grasps at 6 months compared with full-term infants. Weight disturbance seems to change the intrinsic dynamics involved in reaching movements of 5-7-month-old preterm infants.