Chapter 8: Exercise Physiology
Skeletal Muscle
Part 2
Fiber Types and Performance
Power athletes
–Sprinters
–Possess high
percentage of fast fibers
Endurance athletes
–Distance
runners
–Have high
percentage of slow fibers
Others
–Weight
lifters and nonathletes
–Have about ________
slow and ________ fast fibers
Alteration of Fiber Type by Training
Endurance and resistance training
–________________
change fast fibers to slow fibers
–Can result
in shift from ______________ to _____________
Toward more oxidative properties
Training-Induced Changes in Muscle Fiber Type
Age-Related Changes in Skeletal Muscle
Aging is associated with a____________ of muscle mass
–Rate
increases after __________ years of age
Regular exercise training can improve ____________ and _______________
–Cannot
completely eliminate the age-related loss in muscle mass
Types of Muscle Contraction
_______________
–Muscle
exerts force without changing length
–Pulling
against immovable object
–Postural
muscles
Isotonic (dynamic)
–________________________
Muscle shortens during force production
–________________________
Muscle produces force but length increases
Isotonic and Isometric Contractions
Speed of Muscle Contraction and Relaxation
Muscle twitch
–Contraction
as the result of a single stimulus
–Latent
period
Lasting only ~5 ms
–Contraction
Tension is developed
40 ms
–Relaxation
50 ms
Muscle Twitch
Force Regulation in Muscle
Types and number of motor units recruited
–More motor
units = _________ __________
–Fast motor
units = _________ ___________
Increasing stimulus strength recruits ____________ & __________/____________
motor units
Initial muscle length
–ÒIdealÓ
length for force generation
Nature of the motor units neural stimulation
–Frequency of
stimulation
Simple twitch, summation, and tetanus
Relationship Between Stimulus Frequency and Force Generation
Length-Tension Relationship
Simple Twitch, Summation, and Tetanus
Force-Velocity Relationship
At any absolute force the speed of movement is _______________
in muscle with higher percent of __________________ fibers
The maximum velocity of shortening is greatest at the ______________
force
–True for ___________________________
fibers
Force-Velocity Relationship
Force-Power Relationship
At any given velocity of movement the power generated is
greater in a muscle with a higher percent of ___________________________ fibers
The __________________ increases with velocity up to
movement speed of 200-300 degrees¥second-1
–Force
decreases with ______________ movement speed beyond this velocity
Force-Power Relationship
Muscle spindle
–Changes in
muscle length
–Rate of
change in muscle length
–Intrafusal
fiber contains actin & myosin, and therefore has the ability to shorten
–Gamma motor
neuron stimulate muscle spindle to shorten
Stretch reflex
–Stretch on
muscle causes __________________ contraction
Muscle Spindle
Receptors in Muscle
Golgi tendon organ (GTO)
–Monitor_____________________
developed in muscle
–Prevents __________________
during excessive force generation
Stimulation results in ______________ ________________ of muscle
Golgi Tendon Organ