Muscle fatigue is an exercise-induced reduction in maximal voluntary muscle force. It may arise not only because of peripheral changes at the level of the muscle, but also because the central nervous system fails to drive the motoneurons adequately. Evidence for “central” fatigue and the neural mechanisms underlying it are reviewed, together with its terminology and the methods used to reveal it. Much data suggest that voluntary activation of human motoneurons and muscle fibers is suboptimal and thus maximal voluntary force is commonly less than true maximal force. Hence, maximal voluntary strength can often be below true maximal muscle force. The technique of twitch interpolation has helped to reveal the changes in drive to motoneurons during fatigue. Voluntary activation usually diminishes during maximal voluntary isometric tasks, that is central fatigue develops, and motor unit firing rates decline. Transcranial magnetic stimulation over the motor cortex during fatiguing exercise has revealed focal cha...

Spinal and Supraspinal Factors in Human Muscle Fatigue

Non-invasive electrical and magnetic stimulation of the brain, spinal cord and roots: basic principles and procedures for routine clinical application. Report of an IFCN committee

1. We stimulated the motor cortex of normal subjects (transcranial magnetic stimulation) while they 1) observed an experimenter grasping 3D-objects, 2) looked at the same 3D-objects, 3) observed an experimenter tracing geometrical figures in the air with his arm, and 4) detected the dimming of a light. Motor evoked potentials (MEPs) were recorded from hand muscles. 2. We found that MEPs significantly increased during the conditions in which subjects observed movements. The MEP pattern reflected the pattern of muscle activity recorded when the subjects executed the observed actions. 3. We conclude that in humans there is a system matching action observation and execution. This system resembles the one recently described in the monkey.

/pdf/motor-facilitation-during-action-observation-a-magnetic-3ukh3fyt23.pdf

Motor facilitation during action observation: a magnetic stimulation study

http://www.cognitiveneuroscience.it/wp-content/uploads/2015/10/Rossini_CliNeuro_2015.pdf

Non-invasive electrical and magnetic stimulation of the brain, spinal cord, roots and peripheral nerves: Basic principles and procedures for routine clinical and research application: An updated report from an I.F.C.N. Committee

http://www.mag2health.com/wp-content/uploads/CLINPH-Guidelines-rTMS.pdf

Evidence-based guidelines on the therapeutic use of repetitive transcranial magnetic stimulation (rTMS)

Non-invasive magnetic stimulation of human motor cortex

This report describes a novel method of stimulating the motor cortex and deep peripheral nerves in humans. The technique, developed in the Department of Medical Physics of Sheffield University, uses a large pulse of magnetic field to induce currents within the body and is painless. The basic principles of magnetic stimulation are described, and the technique is compared with conventional electrical stimulation. Safety aspects are discussed with reference to established clinical electrical and magnetic procedures. The results of the first clinical study using magnetic stimulation are described and show clear central motor pathway slowing in multiple sclerosis patients.

I.L. Freeston

Papers

Non-invasive magnetic stimulation of human motor cortex

Magnetic stimulation of the human brain and peripheral nervous system: an introduction and the results of an initial clinical evaluation.

Clinical evaluation of conduction time measurements in central motor pathways using magnetic stimulation of human brain.

Motor responses to non-invasive brain stimulation in clinical practice

Non-invasive stimulation of motor pathways within the brain using time-varying magnetic fields