The human motor system is unique. It talks, walks and can play the piano from a remarkably early age. But it is difficult to study. One cannot impale single neurones with electrodes or lesion discrete areas of the nervous system in man. However, data gleaned from such elegant experiments in lower species that walk on four feet may not reflect the organisation of human motor mechanisms. John Rothwell is one of a small band of human-motor physiologists who have followed the dictum 'The proper study of mankind is man'. In this book, he brings together what is known about human motor physiology in an eminently readable and critical fashion. Of course, there is a stimulating symbiosis between animal and human experimental motor physiology, and this is effected by the integration of critical information that can only be obtained from work on animals with what is known about man. Many disciplines have interest in the mechanisms of human voluntary movement - physiologists, psychologists, physiotherapists and clinicians, be they neurologists or those working in orthopaedics, physical medicine or rehabilitation. All will find John Rothwell's book invaluable. To the beginner it provides an excellent introduction to the subject. To the expert it presents a coherent review of current knowledge and areas of uncertainty. What is abundantly clear is how much more remains to be discovered about how man controls movement. The stimulus provided by this volume will be invaluable to thought and experiment.
1. Introduction. Plans, Strategies and Actions.- Categories of Muscles.- Problems of Moving.- A Legacy.- 2. Mechanical Properties of Muscles.- Review of Muscle Anatomy.- The Sliding Filament Hypothesis of Muscle Contraction.- Mechanical Properties of Muscle.- Studies on Tetanically Activated Isolated Muscle.- The Length-Tension Relationship.- Twitch Contractions at Different Muscle Lengths.- Force-Velocity Relationship.- The Effect of the Rate of Muscle Stimulation.- Behaviour of Isolated Muscle Stimulated at Subtetanic Rates.- Asynchronous Activation of Muscle.- Length-Tension Relationship at Different Levels of Muscle Activation.- Forced Lengthening of Partially Activated Muscle.- Muscle Mechanics in Intact Man.- Effects of Muscle Properties on Control of Movement.- Effects Arising from the Length-Tension Relationship.- Force Production at Different Muscle Lengths.- Stiffness of Muscle.- Effects Arising from the Force-Velocity Relationship.- Efficiency of Muscle Contraction.- Lengthening Contractions.- Intrinsic Feedback Control of Muscle Contraction.- A Theory of Movement Control which Makes Use of the Mechanical Properties of Muscle.- 3. The Motor Unit.- The Concept of the Motor Unit.- Twitch and Tonic Muscle Fibres.- Physiological Investigation of the Motor Unit.- Territory and Size of Motor Units.- Differences in the Contraction of Motor Units.- Speed of Contraction and Fatiguability.- Twitch Tension and Specific Twitch Tension.- Post-tetanic Potentiation.- Size and Conduction Velocity of Motor Axons.- Summary.- Histochemical and Biochemical Classification of Muscle Fibres.- Correlation between Histochemical and Physiological Classifications of Motor Units.- Some Electrophysiological Properties of Motoneurones.- Synaptic Inputs to Motoneurones.- Input Resistance of Motoneurones.- Firing Patterns of Motoneurones.- Control of Motor Units and their Recruitment Order.- Mechanisms Responsible for the Recruitment Order of Motoneurones.- Exceptions to the Normal Order of Recruitment.- Examples of Motoneurone Recruitment during Normal Movement.- The Study of Motor Units in Human Physiology.- Recording Motor Units in Man.- Histochemistry of Human Motor Units.- Mechanical Properties of Human Motor Units.- Recruitment Order of Motor Units in Man.- Changes in Recruitment Order.- Firing Frequency of Human Motor Units.- Gradation of Force in Human Muscle Contraction.- Muscle Fatigue.- Pathophysiology of the Motor Unit.- The Normal Electromyogram.- The Electromyogram in Neurogenic Diseases.- The Electromyogram in Myopathic Diseases.- Changes in Firing Rate and Recruitment Order of Motor Units.- 4. Proprioceptors in Muscle, Joint and Skin.- Muscle Receptors: I. The Muscle Spindle.- Anatomy.- Physiology of Spindle Afferent Responses.- The Effect of ? Activity on Spindle Afferent Responses.- Response of Spindle Endings to Very Small Displacements.- Muscle Receptors: II. Golgi Tendon Organs.- Anatomy.- Physiology of Golgi Tendon Organ Responses.- Muscle Receptors: III. Other Types of Ending.- Joint Receptors.- Anatomy.- Physiology.- Cutaneous Mechanoreceptors.- Recordings from Human Afferent Nerve Fibres.- Muscle Spindles.- Golgi Tendon Organs.- Cutaneous Mechanoreceptors.- Contribution of Muscle Afferents to Sensation.- 5. Reflex Pathways in the Spinal Cord.- Classification of Nerve Fibres.- Reflex Pathways from la Muscle Spindle Afferents.- Anatomy.- Electrophysiology.- Monosynaptic Excitation.- Disynaptic Inhibition.- Polysynaptic Actions.- Reflex Pathways from lb Tendon Organ Afferents.- Anatomy.- Electrophysiology.- Reflex Pathways from Group II Muscle Afferents and the 'Flexor Reflex Afferents'.- Anatomy.- Electrophysiology.- The Renshaw Cell.- Integration in Spinal Reflex Pathways.- Convergence onto the la Inhibitory Interneurone.- Convergence onto Ib Interneurones.- Comments on Convergence.- Presynaptic Inhibition.- 6. Functional Consequences of Activity in Spinal Reflex Pathways.- The Stretch Reflex in Animals.- Stretch Reflex