Experimental Brain Research

, Volume 154, Issue 4, pp 417–427

Postural feedback responses scale with biomechanical constraints in human standing

Research Article
  • 816 Downloads

Abstract

We tested whether human postural responses can be described in terms of feedback control gains, and whether these gains are scaled by the central nervous system to accommodate biomechanical constraints. A feedback control model can describe postural responses for a wide range of perturbations, but biomechanical constraints—such as on the torque that can be exerted on the ground—make a single set of feedback gains inappropriate for all perturbations. To observe how postural responses change with perturbation magnitude, we applied fast, backward perturbations of magnitudes 3–15 cm to 13 healthy young volunteers (4 men, 9 women, aged 20–32 years). We used a 3-segment, sagittal-plane biomechanical model and a linear state feedback controller to reproduce the observed postural responses. Optimization was used to identify the best-fit feedback control gains for each trial. Results showed that trajectories of joint angles and joint torques were scaled with perturbation magnitude. This scaling occurred gradually, rather than abruptly changing at magnitudes where biomechanical constraints became active. Feedback gains were found to fit reasonably well with data (R2=0.92) and to be multivariate and heterogenic in character, meaning that the torque produced at any joint is generally a function of motions not only at the same joint, but other joints as well. Hip gains increased and ankle gains decreased nearly linearly with perturbation magnitude, in accordance with biomechanical limitations on ground reaction torque. These results indicate that postural adjustments can be described as a single feedback control scheme, with scalable heterogenic gains that are adjusted according to biomechanical constraints.

Keywords

Balance Equilibrium Posture Motor control Biomechanics 

References

  1. Adkin AL, Frank JS, Carpenter MG, Peysar GW (2000) Postural control is scaled to level of postural threat. Gait Posture 12:87–93PubMedGoogle Scholar
  2. Allum JH, Honegger F (1998) Interactions between vestibular and proprioceptive inputs triggering and modulating human balance-correcting responses differ across muscles. Exp Brain Res 121:478–494PubMedGoogle Scholar
  3. Barin K (1989) Evaluation of a generalized model of human postural dynamics and control in the sagittal plane. Biol Cybern 61:37–50PubMedGoogle Scholar
  4. Bonasera SJ, Nichols TR (1994) Mechanical actions of heterogenic reflexes linking long toe flexors with ankle and knee extensors of the cat hindlimb. J Neurophysiol 71:1096–1110PubMedGoogle Scholar
  5. Burleigh AL, Horak FB, Malouin F (1994) Modification of postural responses and step initiation: evidence for goal-directed postural interactions. J Neurophysiol 72:2892–2902PubMedGoogle Scholar
  6. Diener HC, Horak FB, Nashner LM (1988) Influence of stimulus parameters on human postural responses. J Neurophysiol 59:1888–1905PubMedGoogle Scholar
  7. Dietz V (1993) Gating of reflexes in ankle muscles during human stance and gait. Prog Brain Res 97:181–188PubMedGoogle Scholar
  8. Henry SM, Fung J, Horak FB (1998) EMG responses to maintain stance during multidirectional surface translations. J Neurophysiol 80:1939–1950PubMedGoogle Scholar
  9. Holstege G (1998) The anatomy of the central control of posture: consistency and plasticity. Neurosci Biobehav Rev 22:485–493CrossRefPubMedGoogle Scholar
  10. Horak FB, Kuo AD (2000) Postural adaptation for altered environments, tasks, and intentions. In: Winters J, Crago P (eds) Biomechanics and neural control of movement, Chapt 19. Springer, New York, pp 267–281Google Scholar
  11. Horak FB, Macpherson JM (1996) Postural orientation and equilibrium. In: Shepard J, Rowell L (eds) Exercise: Regulation and Integration of Multiple Systems. (Handbook of physiology, Sect 12) Oxford University Press, New York, pp 255–292Google Scholar
  12. Horak FB, Nashner LM (1986) Central programming of postural movements: adaptation to altered support-surface configurations. J Neurophysiol 55:1369–1381Google Scholar
  13. Horak FB, Diener HC, Nashner LM (1989) Influence of central set on human postural responses. J Neurophysiol 62:841–853PubMedGoogle Scholar
  14. Horak FB, Nutt JG, Nashner LM (1992) Postural inflexibility in parkinsonian subjects. J Neurol Sci 111:46–58PubMedGoogle Scholar
  15. Horak FB, Frank J, Nutt J (1996) Effects of dopamine on postural control in Parkinsonian subjects: scaling, set and tone. J Neurophysiol 75:2380–2396PubMedGoogle Scholar
  16. Hughes MA, Schenkman ML, Chandler JM, Studenski SA (1995) Postural responses to platform perturbation: kinematics and electromyography. Clin Biomech 10:318–322CrossRefGoogle Scholar
  17. Kolb FP, Lachauer S, Diener HC, Timmann D (2001) Changes in conditioned postural responses. Comparison between cerebellar patients and healthy subjects. Acta Physiol Pharmacol Bulg 26:143–146PubMedGoogle Scholar
  18. Kuo AD (1995) An optimal control model for analyzing human postural balance. IEEE Trans Biomed Eng 42:87–101PubMedGoogle Scholar
  19. Kuo AD (1998) A least-square estimation approach to imporving the precision of inverse dynamics computations. Trans ASME Bioeng 120:148–159Google Scholar
  20. Kuo AD, Zajac FE (1993) A biomechanical analysis of muscle strength as a limiting factor in standing posture. J Biomech 26:137–150PubMedGoogle Scholar
  21. Kuo AD, Speers RA, Peterka RJ, Horak FB (1998) Effect of altered sensory conditions on multivariate descriptors of human postural sway. Exp Brain Res 122:185–195PubMedGoogle Scholar
  22. Maki BE, Ostrovski G (1993) Scaling of postural responses to transient and continuous perturbations. Gait Posture 1:93–104Google Scholar
  23. Nashner LM (1976) Adapting reflexes controlling the human posture. Exp Brain Res 26:59–72PubMedGoogle Scholar
  24. Nashner LM, Cordo PJ (1981) Relation of automatic postural responses and reaction-time voluntary movements of human leg muscles. Exp Brain Res 43:395–405PubMedGoogle Scholar
  25. Nashner LM, McCollum G (1985) The organization of human postural movements: a formal basis and experimental synthesis. Behav Brain Sci 8:135–172Google Scholar
  26. Nauck D, Klawonn F, Kruse R (1997) Foundations of neuro-fuzzy systems. Wiley, ChichesterGoogle Scholar
  27. Runge CF, Shupert CL, Horak FB, Zajac FE (1999) Ankle and hip postural strategies defined by joint torques. Gait Posture 10:161–170PubMedGoogle Scholar
  28. Schmidt RA, Lee TD (1999) Motor control and learning, 3rd edn. Human Kinetics, Champaign, ILGoogle Scholar
  29. Shittowski K (1985) NLQPL: A FORTRAN-subroutine solving constrained nonlinear programming problems. Ann Op Res 5:485–500Google Scholar
  30. Sinha T, Maki BE (1996) Effect of forward lean on postural ankle dynamics. IEEE Trans Rehabil Eng 4:348–359PubMedGoogle Scholar
  31. Speers RA, Paloski WH, Kuo AD (1998) Multivariate changes in coordination of postural control following spaceflight. J Biomech 31:883–889CrossRefPubMedGoogle Scholar
  32. Timmann D, Horak FB (1998) Perturbed step initiation in cerebellar subjects. 1. Modifications of postural responses. Exp Brain Res 119:73–84PubMedGoogle Scholar
  33. Yeadon MR, Morlock M (1989) The appropriate use of regression equations for the estimation of segmental inertia parameters. J Biomech 22:683–689PubMedGoogle Scholar
  34. Zettel JL, McIlroy WE, Maki BE (2002) Can stabilizing features of rapid triggered stepping reactions be modulated to meet environmental constraints? Exp Brain Res 145:297–308CrossRefPubMedGoogle Scholar

Copyright information

© Springer-Verlag 2004

Authors and Affiliations

  1. 1.Department of Mechanical EngineeringUniversity of MichiganAnn ArborUSA
  2. 2.Neurological Sciences Institute of Oregon Health Sciences UniversityPortlandUSA
  3. 3.Jenks Vestibular Physiology LaboratoryMassachusetts Eye and Ear Infirmary (Room 421)BostonUSA

Personalised recommendations