neuromuscular mechanics
A component of motor control that refers to the relationship between the neural control of movement and the mechanical output of muscle
motor unit pool
A grouping of motor units in the spinal cord that activate a particular muscle or muscle group
innervation ratio
The ratio of one neuron to the number of muscle fibers it innervates; smaller innervation ratios enable finer movement control.
all-or-none principle
Refers to the activation of muscle fibers within each motor unit, in which all muscle fibers within a motor unit contract or none contract in response to the neuron's action potential
size principle of recruitment
A property of motor unit activation in which motor units are recruited in order from small units to large units, largely due to the neuron size and the stimulation energy needed to reach threshold
electromyography
A technique to detect and record muscle electrical activity using electrodes within the muscle or on the skin over a muscle
mechanomyography
A technique used to assess muscle activity by detecting minute vibra- tions during contractions using special vibration sensors placed on the skin surface
recruitment
A mechanism to change muscle force output by increasing or decreasing the number of active motor units.
rate coding
Regulation of the firing rate of action potentials to modify muscle force output
coordination
Refers to the patterning of the body, limb segments, and muscles among themselves and to the external environment. See intramuscular coordination and intermuscular coordination
firing rate
The number of action potentials per second traveling down a neuron or along a muscle fiber; firing rate influences muscle force production and may range from a minimum of 5 to 8 Hz to a maximum of 120 Hz for ballistic contractions.
intramuscular coordination
The patterning and use of motor units within a muscle or motor unit task groups across muscles to produce effective and efficient forces and movements
Intermuscular coordination
The patterning of muscle groups, limbs, and body segments to produce efficient and purposeful movements in the context of environmental and task demands
discharge patterning
Refers to specific manipulation of a motor neuron's firing rate to meet specific task demands, for instance, a sequence of two to three rapid action potentials sent to the muscle fibers may greatly increase the tension output of the muscle
muscle wisdom
A form of discharge patterning that refers to the change (slowing) in discharge rates during fatigue.
compartmentalization
Refers to smaller and independently controlled groups of muscle fibers contained within a single muscle or across a group of muscles
synchronization
A motor unit discharge pattern whereby activation of different motor units, especially the firing rates of already active units, become timed to fire all at the same time
excitable
A property of some biological tissues (e.g., muscle tissue) referring to the tissue's capability to respond to electrical impulses
extensibility
The capability of muscle and tendon tissue to stretch
elasticity
The capability of the muscle and tendon to recoil from stretch
contractility
Muscle tissue property enabling it to produce force by shortening.
length-tension curve
A model of the relationship between the force a muscle can generate or store to the length of the muscle's contractile and elastic elements
concurrent movements
Movements, such as vertical jumping, in which an involved multijoint muscle is engaged in contractile shortening at one joint to move a load, while at the opposite joint is being stretched
countercurrent
Movements in which an involved multijoint muscle is engaged in contractile shortening to move loads at the muscle's opposing joints or engaged in lengthening at both opposing joints; results in a rapid and large amount of shortening during contraction or a rapid and large amount of stretch during lengthening
force-velocity curve
The relationship between muscle contraction velocity and force output; illustrates that high forces can only be generated at slow speeds
agonists
Muscles directly involved in producing desired movement; can be either prime movers or synergists
synergists
Muscles that work with agonist muscles to perform specific joint or limb movements
antagonist
Muscles that oppose the action of the agonists
stabilizers/fixator
Muscles that usually contract statically to stabilize a body part or other muscle against the pull of contracting muscles or movement of body parts; many categorized as postural muscles
neutralizers
Muscles acting to prevent an undesired action of other active muscles