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tendon insertion
is a genetic factor contributing to strenght tha tdoes not change with training
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action force
the force applied by an individual to an ovjedt with the intent to accelerate, deccelerate, stopl maintain, or change the direction of the object
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reaction force
produced in response to the action. third law of motion, for ever action there is an equal and opposite reaction. the reactive force is equal and opposite of the action force
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ground reaction force
the ground supplies an equal and opposite force in response to a force applied to the ground by the athlete during locomotion. the ground reation force enables the athlete to run
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friction
- act to oppose relative motion of these two surfaces
- friction causes stability at the point of contactand prevents one object from sliding past the other
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coeffiecient of friction
- the maximum frictional force is the product of the reactive force and a quantiy
- the numerical representation of the two contact surfaces
- chalk increases this friction
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static friction
- acts between two objects not moving relative to each other where there is sufficient stability between the contact surfaces
- static friction between a players feet and ground plays a role in shoe desine
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dynamic friction (sliding)
- acts between two surfaces moving relative to each other, resulting in sliding
- ice
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intra abdominal pressure iap
the pressure developed within the abdominal cavity during contraction of deep trunk muscles and the diaphragm
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neural drive
the magnitude of the signal is is critical in dtermining the final output , wgich could be teh expression of muscular strenght and power
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increases in neural drive occur via increase in
agonist muslce recruitment, firing rat, and the timing pattern of discharge during high intensity muscular contractions
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central nervous system
consits of brain and spinal cord
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peripheral nervous system constist of two major divisions
- snensory
- motor
- 31 pairs of spinal nerves exist and exit on the posterior sensory and aniterior motor root of the spinal cord
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sensory nervous system
detects various stimulu and conveys this infomation afferently to cns
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motor nervous system consist of two major divisions
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somatice nervous system
conveys infromation from the cns efferently(away from the cns) to the skeletal muscle ultimately leading to muscle contraction and fatigue
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autonomic system
consist of nerves conveying efferent information to smooth muscles, cardiac muscle, and other glands , tissues, and organs
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ANS consits of what to systems
- parasympathetic
- sympathetic nervous system
- both preparing the body for the stress of exercise and retuning the body back to normal resting conditions
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parasympathetic nervous system
decrease excitment
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sympathetic
excitement increase in the heart rate
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neurons
are the actual nerve cells with the ability to conmmunicate with other tissues and nerves.
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supporting cells
play key stability roles troughout the cns
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sensory neurons tend to be------- whereas motor neurons are ------
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dedrites
receive input from other nerve cells
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cell body contains the organells responsible for
- protein snthesis
- transport
- energy metabolism
- packaging and plays the critical role in integratin stimuli from other neurons from within the cns to determine if and how much stimuli will make its way to skeletal muscle
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axons
are long processes that are reponsible for communicationg with target tissuess
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axon hillock
is the area where the action potential is initiated once the critical threshold is reaxhed
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myelin sheath
fatty tissue wrapped around the axons wichi greatly increases the speed of transmission.
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presynaptic terminal
the end of the axon branches
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propagation
- ion movement down axon at nodes of ranvier
- sodium and potassium
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action potential consist of three major events
- integration
- propagation
- neurotransmitter release
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brainstem consting of
- medulla oblongata
- midbrain
- pons
- and reticular fromation
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diencephalon consits of
- thalamus
- gypothalamus
- pineal body
- epithalamus
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desecending coricospinal or pyramidal tracts
are large collection of axons linking the cerbral cortex to the spinal cord
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the motor pathway is characterized by
neurons in the brain forming synapses with other nerves that eventually make their way down the spinal cord to the exact anterior root of exit for innervation of skeletal muscle
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recrutment
thee vouluntary activation of motor units during effort
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motor units are recruited and decruited in an orderl progression based on
the size principle
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size principle
- states the motor units are recruited in succession from smaller slow twitch to largere fast twitch units based on each acivation threshold and firing rate.
- small units are recruited first for mor intricate control
- larger units are recruited later to supplu substantial force for high intesnsity contractions
- 84-90% of motor units are recruited here
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what is the most imoportant determinate of motor unit recruitment
activation threshold
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what is mandatory in order to continually activate an optimal amout of muscle mass
progressive overload
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smaller muscles rely on what to enhance force and power production
increasing firing rates
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larger muscles rely more on for force and power
recruitment
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------ enhances firing rates of recurited motor units
anaerobic
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synchronization
- occurs when two or more motor units fire at fixed time intervals
- may be advantageous for burst of strenght or powr needed in a short period of time
- greater motor synchronization has been shown after rt
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antagonist muscles
- during movement increases join stability, movement coordination, and reduces the risk of injury
- can be counterproductive because it may counteract the effects of agonist muscles
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what affect the magnitude of of antagonist cocontraction
- muscle group
- velocity and type of muscle axtion
- intensity
- joint position
- and injury status
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whats the key transmitter between a motor nerve and skeltal muscle
acetycholine
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neuromuscular junction refers to
- the nerve terminal
- space
- and muscle fiber membrane
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the two proprioceptors critical to exercise and sports performance are
- golgi tendon organs
- muscle spindles
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golgi tendon organs
- located at the muscle tendon junction
- primary role is to convey information regarding muscle tension to the cns.
- as muscle tension increase so does the amount of stretch to the gtos
- once a threshold level of tension is attained, gto activity increases greatly and it response is to cause agonist muscle relaxation and anagonist muscle excitation
- body defense mechanism to protect the body form excessive damage
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muscle spindles
- proprioceptors located within muscle fibers
- consits of two chains nuclear chain and nuclear bag
- respond to the magnitude of change in muscle length, the rate of change of length, and convey information to the cns regarding static changes in muscle lenght or joint angle
- enhance human performance
- initiate the stretch reflex
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stretch reflex
- monosynaptic reflex- a snseory nerve directly synapses with motor nerve in spinal cord
- where muscle force production is enhanced when the muscle is previoulsy stretched
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electromyography emg
- quantifies the level of electrical activity to a skeletal muscle
- reflects greater neural activation
- increased recruitment, rate, synchronization, golgi tendon inhibition cannot be determinded
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why do emg decline in when hypertrophy takes place
muscle fibers are capable of providing more tension
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emg increases or is higher when
- the intensity is high
- the lifiting velocity is fast
- and con muscle actions is used
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cross eductaion
- strength and endurance gained in the nontrained limb during unilateral training.
- the strength increase is accompanied by greater emg activity in the trained and nontrained limbs.
- edurance may increase in the untrained limb as well
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unilateral training
may be useful in improving functional performance and very useful for injured individuals because partial training effect may be gained by the inhured limb during tim of immobilization or greatly reduced activity
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bilateral deficit
the maximal force produced by both limbs contractin bilaterally in smaller than the sum of the limbs contracting unilaterally
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