Exam ! Flashcards
Fast Motor Units (Type IIx)
high force production, fast contraction speed, low fatigue resistance, has a systematic increase in tension; fast glycolytic systems used
Fast Fatigue-Resistant Motor Units (Type IIa)
moderate force production, fast contraction speed, moderate fatigue resistance, has a systematic increase in tension, uses fast oxidative systems
Slow Motor Units (Type I)
low force production, slow contraction speed, highly fatigue resistant, no systematic increase in tension, slow oxidative; “dark meat” because of myoglobin; high oxidative capacity
High Oxygen Consumption =
higher VO2, higher aerobic capacity, more slow twitch fibers
Low Oxygen Consumption =
lower VO2, lower aerobic capacity, less slow twitch fibers
Motor Unit
a single nerve and every muscle fiber it innervates; come in different ratios of muscle fibers per motor neuron depending on how fine the movement is
Intensity v. Motor Units Recruited
as intensity increases, more motor units are recruited; force generation dictates motor units; light intensity/load means more type I motor units are available; heavy intensity means type IIa and IIx are much more available; moderate load means all three types are used equally
Size Principle
frequency of motor unit utilization is directly related to the size of the motor unit; smaller motor neurons are utilized more frequently and vice versa; motor units with smaller motor neurons (type I) will be recruited first
All or None Law
if you fire a motor neurons, all of their muscle fibers have to fire as well
Twitch
the smallest contractile response of a muscle fiber or a motor unit to a single electrical stimulus
Summation
a series of three stimuli is rapid sequence, before complete relaxation from the first stimulus, can elicit an even greater increase in force or tension
Tetanus
continued stimulation at higher frequencies can cause this, which results in the peak force or tension of the muscle fiber or motor unit
Rate Coding
the process by which the tension of a given motor unit can vary from that of a twitch to that of tetanus by increasing the frequency of stimulation of that motor unit
Asynchronous Recruitment
out of rhythm recruitment; “out of synch”; the motor units take turns, while some are contracting others are recovering; allows for endurance and resistance to fatigue; looks like a smooth contraction but all taking turns; sub max
Synchronous Recruitment
when you want to exert maximal force; all motor units fire at the same time; as we get stronger we get better at doing this;
Absolute Maximum Force
golgi tendon organs and muscle spindle prevent us from reaching this; but if we train hard enough we can overcome this; we also overcome this in fight or flight situations
Relative Maximum Force
When we perceive muscle fatigue; one rep max; we’ve all done this in the gym
Motor Unit Categorization
Two types based on speed of contraction (slow twitch and fast twitch) and three types because of metabolic capabilites (glycolytic or oxidative)
How is Muscle Fiber Type Determined
muscle biopsy or histochemical staining
Distribution of Fiber Types (Vo2 v. muscle fiber)
High oxygen consumption means higher VO2, higher aerobic capacity, more slow twitch fibers
Summation
a series of three stimuli in rapid sequence, before complete relaxation from the first stimuli; can elicit an even greater increase in force or tension
Absolute Maximal Force
golgi tendon organs and muscle spindle prevents us from reaching this; fight or flight response or extreme training can overcome these inhibitory forces
Relative Maximal Force
we all have done this when we’re in the gym; what we perceive as our muscle’s maximal force
Recruitment Order
motor units are recruited in sequential order and fired in this order; allows us to become very proficient at what we do; learned through repetitions
Principles of Increasing Strength
overload and progression
Overload
the load needs to be greater than we’re used to; submitting a system of the body to a load greater than what it’s used to ; as this increases, frequency can decrease
Progression
we have to change and increase the load over time in order to get stronger
Strength
maximal ability to exert force once
Power
the maximal force in the least amount of time; to increase power we can increase strength or decrease time
Concentric Muscle Contraction
a muscle’s principle action- shortening; thin filaments are pulled toward the center of the sarcomere; joint movement is produced;
Isometric Program (advantages)
same length of muscle and no movement; cheap, little or no equipment needed; good to use for strengthening a specific weakness in a range of motion; used in rehabilitation as starting points;
Isometric Programs (Disadvantages)
time consuming, adaptation only occurs at the specific joint angle of isomeetric contraction
Isotonic Programs
same tension; could be free weights or machines (fixed v. variable resistance)
Isotonic Programs: Variable Resistance (Advantages)
gives you a higher load where you can use it; near maximal throughout ROM; allows working on a specific muscle group without fatiguing stabilizers
Isotonic Programs: Variable Resistance (Disadvantages)
does not work stabilizing muscles due to the sled or seat; expensive
Isotonic Programs: Fixed Resistance (Advantages)
trains prime movers but also stabilizers (functional); more like what we’re going to do in every day life; relatively inexpensive
Isotonic Programs: fixed resistance (disadvantages)
does not provide max resistance throughout the ROM; max resistance only at weakest point in ROM; somewhat dangerous
Isokinetic Programs
same speed; closest to max loading throughout ROM; allows training at higher speed; excellent for research or rehab; air pressurized or hydraulics;
Isokinetic Programs (Disadvantages)
extremely expensive; fragile under heavy use
Strength/Endurance Continuum
endurance is less weight more times; strength is more weight less times
Exercise Order
multiple joint movements, large muscle groups, power exercises all are first
Recovery Periods
very important! Minimum amount of time to wait before another set; higher the load, the longer the recovery; more than 24 hours of rest
Why do we get stronger?
hypertrophy, hyperplasia, better motor unit recruitment, an increase in excitation and a decrease in inhibition, and remodeling
Hypertrophy
an increase in muscle size that leads to an increase in muscle strength; occurs due to an increase in myofibrils; this leads to an increase in fluid and more CT to protect the increase in force;
Transient Hypertrophy
right after an exercise bout; due to edema formation from plasma fluid; disappears within hours
Chronic Hypertrophy
long term increase in size; actual structural change in muscle; maximized by high velocity eccentric training; disrupts sarcomere Z lines; cause the most damage
Neural Control
muscle plasticity allows neural adaptations to be made to increase strength; synchronous recruitment leads to strength gain; can also decrease inhibitory impulses; also may decrease coactivation of antagonists
Protein Synthesis in Exercise
muscle protein content is always changing; during exercise, protein synthesis decreases and increases in protein degradation; after exercise, protein synthesis increases and decreases protein degradation
Hyperplasia
increase in the number of muscle fibers; may or may not play a major role
Short Term Increases in Muscle Strength
substantial increase in 1 RM due to an increase in voluntary neural activation; neural factors critical in the first 8 to 10 weeks
Longer Term Increase in Strength
associated with significant fiber hypertrophy; net increase in protein synthesis; hypertrophy a major factor
Ways Hyperplasia Occurs
Fiber splitting or satellite cells
