75-9  Sat Jan 2  Swing it like a piglet Mielke, F*; Van Wassenbergh, S; Van Ginneken, C; Aerts, P; University of Antwerp; University of Antwerp; University of Antwerp; University of Antwerp falk.mielke@uantwerpen.be

Terrestrial locomotion necessarily involves a stance phase (to hold the weight) and a swing phase (to advance the stance positions). Of those, the latter is sometimes supposed to be partially passive, i.e. negligible in terms of energy expenditure. For example, the swing phase has been described as “ballistic” (cf. Mochon and McMahon, 1980), which implies that the limb is “shot off” at given conditions, then passively moves, prior to impact. However, such sophisticated locomotor patterns require precise coordination to be energy efficient. There is evidence that young individuals fail to coordinate efficient swings. We present data from locomoting piglets (age 1-5 days) to measure how energy efficient their swing actually is. Using recordings from biplanar x-ray, we are able to quantify inverse dynamic balances and energetics at the joint level in high detail. Our data offers insights into a crucial developmental phase of these animals, showing that “swinging it right” takes some practice.