The control of timing and amplitude of EMG activity in landing movements in humans

The control of self‐initiated falls from different heights was studied. The objective of the study was to investigate in a quantitative manner the modulation of EMG timing (i.e. onset from take‐off and duration from onset to touch‐down) and amplitude (before and after foot contact) as a function of fall height. The muscles studied were m. soleus and m. tibialis anterior. Kinematic (ankle joint angle) and kinetic (ground reaction force) variables were also measured. Six subjects took part in the experiments that consisted of ten landings from each of five heights (0.2, 0.4, 0.6, 0.8 and 1 m) onto a force platform. We found a consistent pattern of co‐contraction before and after touch‐down across the fall heights studied. In both muscles, the onset of pre‐landing EMG activity occurred at a longer latency following take‐off when landing from greater heights. The absolute EMG duration was affected to a lesser extent by increasing fall height. These findings suggest that the onset of muscle activity of the muscles studied prior to foot contact is timed relative to the expected time of foot contact. Pre‐ and post‐landing EMG amplitude tended to increase with height. Despite a doubling in the magnitude of ground reaction force, the amplitude of ankle joint rotation caused by the impact remained constant across heights. These findings suggest that the observed pattern of co‐contraction is responsible for increasing ankle joint stiffness as fall height is increased. The attainment of an appropriate level of EMG amplitude seems to be controlled by (a) timing muscle activation at a latency timed from the expected instant of foot contact and (b) varying the rate at which EMG builds up.

[1]  Jill L. McNitt-Gray,et al.  Kinematics and Impulse Characteristics of Drop Landings from Three Heights , 1991 .

[2]  F. Lacquaniti,et al.  The role of preparation in tuning anticipatory and reflex responses during catching , 1989, The Journal of neuroscience : the official journal of the Society for Neuroscience.

[3]  P. Dyhre‐Poulsen,et al.  Programmed electromyographic activity and negative incremental muscle stiffness in monkeys jumping downward. , 1984, The Journal of physiology.

[4]  JE Desmedt,et al.  Spinal and Supraspinal Mechanisms of Voluntary Motor Control and Locomotion , 1982 .

[5]  C. Erkelens,et al.  Dependence of autogenic and heterogenic stretch reflexes on pre‐load activity in the human arm. , 1991, The Journal of physiology.

[6]  C. Gielen,et al.  Long‐latency stretch reflexes as co‐ordinated functional responses in man. , 1988, The Journal of physiology.

[7]  H. Cotta.  [On the physiology of joints]. , 1966, Langenbecks Archiv fur Chirurgie.

[8]  G. Jones,et al.  Observations on the control of stepping and hopping movements in man , 1971, The Journal of physiology.

[9]  D. N. Lee.  The optic flow field: the foundation of vision. , 1980, Philosophical transactions of the Royal Society of London. Series B, Biological sciences.

[10]  R Greenwood,et al.  Landing from an unexpected fall and a voluntary step. , 1976, Brain : a journal of neurology.

[11]  J. Tresilian,et al.  Perceptual and cognitive processes in time-to-contact estimation: Analysis of prediction-motion and relative judgment tasks , 1995, Perception & psychophysics.

[12]  H W Thompson,et al.  Landing from a jump: the role of vision when landing from known and unknown heights. , 1995, Neuroreport.

[13]  H Jahnsen,et al.  Programmed pattern of muscular activity in monkeys landing from a leap. , 1978, Acta physiologica Scandinavica.

[14]  E B Simonsen,et al.  Dynamic control of muscle stiffness and H reflex modulation during hopping and jumping in man. , 1991, The Journal of physiology.

[15]  A Prochazka,et al.  Reflexes in cat ankle muscles after landing from falls. , 1977, The Journal of physiology.

[16]  J. Wann.  Anticipating arrival: is the tau margin a specious theory? , 1996, Journal of experimental psychology. Human perception and performance.

[17]  G. Jones,et al.  Muscular control of landing from unexpected falls in man , 1971, The Journal of physiology.

[18]  David N. Lee,et al.  A Theory of Visual Control of Braking Based on Information about Time-to-Collision , 1976, Perception.

[19]  Richard B. Stein,et al.  What muscle variable(s) does the nervous system control in limb movements? , 1982, Behavioral and Brain Sciences.

[20]  Francesco Lacquaniti,et al.  Automatic control of limb movement and posture , 1992, Current Opinion in Neurobiology.

[21]  P. Devita,et al.  Effect of landing stiffness on joint kinetics and energetics in the lower extremity. , 1992, Medicine and science in sports and exercise.

[22]  D Schmidtbleicher,et al.  Interaction between pre‐activity and stretch reflex in human triceps brachii during landing from forward falls. , 1981, The Journal of physiology.

[23]  N. A. Borghese,et al.  Internal models of limb geometry in the control of hand compliance , 1992, The Journal of neuroscience : the official journal of the Society for Neuroscience.

[24]  J L McNitt-Gray,et al.  Kinetics of the lower extremities during drop landings from three heights. , 1993, Journal of biomechanics.

[25]  G. Davis,et al.  Visual Timing of Muscle Preactivation in Preparation for Landing , 1989 .

[26]  V. Dietz,et al.  Pre-innervation and stretch responses of triceps bracchii in man falling with and without visual control , 1978, Brain Research.