Stretch reflex distinguished from pre-programmed muscle activations following landing impacts in man.

摘要: The landing movement is a convenient model for the study of several fundamental aspects motor control, one which interaction between central programming and stretch reflexes. When human or an animal jumps down from height there increase in amplitude activation leg muscles during flight phase (Greenwood & Hopkins, 1976; Santello McDonagh, 1998) prior to impact with ground. this activity proportional fall timed moment (Prochazka et al. 1977; 1998). It generally accepted that electromyographic (EMG) immediately preceding does not arise reflex pre-programmed origin (Melvill Jones Watt, 1971; present experiments investigate occurs after impact, still matter dispute. Some authors have concluded weak McKinley 1983) (Dyhre-Poulsen Laursen, 1984; Dyhre-Poulsen 1991). Others suggested it response Prochazka Dietz 1981). The purpose was clearly distinguish components response. subjects jumped onto floor below. electromyogram joint rotation records taken passage through false surface were compared when subject executed another solid at same distance Previous studies had shortcomings. First, experienced unexpectedly lengthened more than once 1976). Thus all trials first, may been correctly anticipated, anticipated presented presented. If such are averaged together (e.g. Noth, 1981) then true result become smeared out by differences these conditions, example time point programme switched on off. Second, foot reached ground first stepping down, allowing possibility lowered supporting upper stair Third, step great enough evoke strong Fourth, real too short determine whether programmed ended 1984). To avoid shortcomings, arranged so each surprise condition only once, two-footed used, sufficient produce high forces elapsed long reveal later stages activity.