Locomotion

Abstract

Locomotion is an animal's ability to move itself from place to place. Locomotion requires the movements of the body or specialised parts of the body to generate propulsive forces on land, water or air. Muscles produce these forces in multicellular organisms. Muscle specialisation, mechanics and skeletal form combine to establish the speed, efficiency and endurance of locomotion. Most locomotor movements involve the rhythmic, co‚Äźordinated contractions of numerous muscles with the basic motor pattern provided by networks of neurons called central pattern generators (CPGs). In vertebrates, the integration of sensory information into CPGs occurs primarily within the spinal cord. However, the supraspinal integration of sensory information is more important in humans. Effective locomotion also requires the correct orientation of the body with respect to the environment, and this is particularly important in humans.

Key Concepts:

  • The type of motor unit used in locomotion is dependent on the speed of locomotion.

  • Specific muscle forces produced during locomotion are almost independent of body size.

  • Energy is stored and released by tendons.

  • Central pattern generators produce the rhythmic alternation flexion/extension bursts of muscle activity associated with locomotion.

  • Afferent feedback reinforces the locomotor muscle activity and controls the phase transition from stance to swing.

  • Locomotion is initiated by command neurons located in the brain stem and lateral hypothalamus.

  • Information from the somatosensory, vestibular and visual systems is used to provide stability for bipedal human walking.

  • Many of the concepts about the control of locomotion derived from animal studies apply to humans; however, human walking requires greater supraspinal control than that for other animals.

Keywords: walking; proprioceptors; motor control; muscle; biomechanics

Figure 1.

Orderly recruitment of motor units in the ankle extensor muscle, medial gastrocnemius (MG), of the cat. The progression from standing to walking to running to jumping is associated with the progressive recruitment of slow (S – dark shading), fast fatigue resistant (FR – mid‐grey shading), fast intermediate (F(int) – light shading) and fast fatiguing (FF – no shading) motor units. The nonlinear increase in force with recruitment is due to the relatively small forces produced by slow motor units. From Walmsley et al.. Copyright © 1978 The American Physiological Society.

Figure 2.

Scaling of muscle mechanics in the legs of mammals. (a) As the size of animals increases, the legs become less bent. This reduces the moment arm (R) of the ground reaction force (GRF) relative to the muscle moment arm (r). T, force on ankle extensor muscle. (b) The effective mechanical advantage (EMA) increases with size (solid line). This increase ensures that the stresses in bones and muscles are similar in animals of different sizes. The exception to this rule is found in kangaroos (dotted line). Modified with permission from Bennett and Taylor and Biewener . Copyright © 1990 American Association for the Advancement of Science.

Figure 3.

Central pattern generation in the swimming system of the lamprey. (a) Rhythmic bursts of activity recorded from motor axons of the 7th and 19th segments of an isolated spinal cord. Note the alternation of activity on opposite sides and the delay in the onset of activity in the caudal segment. This pattern of activity is very similar to that generated in the same segments of a normal swimming animal. (b) Schematic diagram of the neuronal circuits generating rhythmic reciprocal activity in a single segment. Abbreviations: E, excitatory interneuron; I, inhibitory commissural interneuron; L, inhibitory local interneuron; M, motor neuron; RS, reticulospinal interneuron; SR‐E, excitatory stretch receptor and SR‐I, inhibitory stretch receptor. Modified from Grillner et al.. Copyright © 1995, used with permission from Elsevier Science.

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Further Reading

Alexander RMcN (1988) Elastic Mechanisms in Animal Movement. Cambridge: Cambridge University Press.

Alexander RMcN and Goldspink G (eds) (1977) Mechanics and Energetics of Animal Locomotion. London: Chapman and Hall.

Delcomyn F (1980) Neural basis of rhythmic behavior in animals. Science 210: 492–498.

Getting PA (1989) Emerging principles governing the operation of neural circuits. Annual Review of Neuroscience 12: 185–204.

Grillner S (1981) Control of locomotion in bipeds, tetrapods and fish. In: Brooks VB (ed.) Handbook of Physiology, The Nervous System, Motor Control, vol. 2, sect. 1, pp. 1179–1236. Bethesda: American Physiological Society.

Grillner S, Stein PSG, Stuart DG, Forssberg H and Herman RM (1986) Neurobiology of Vertebrate Locomotion. Hong Kong: Macmillan Press.

Harris‐Warrick RM and Marder E (1991) Modulation of neural networks for behavior. Annual Review of Neuroscience 14: 39–58.

Hultborn H and Nielsen JB (2007) Spinal control of locomotion – from cat to man. Acta Physiologica 189: 111–121.

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Lundberg A (1979) Multisensory control of spinal reflex pathways. Progress in Brain Research 50: 11–28.

Stuart DG and Hultborn H (2008) Thomas Graham Brown (1882–1965), Anders Lundberg (1920–), and the neural control of stepping. Brain Research Reviews 59: 74–95.

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How to Cite close
Grey, MJ(Sep 2010) Locomotion. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002/9780470015902.a0000163.pub2]