Motor Unit Types
1. Fast twitch, fatigable (FF) (fast motor unit)
-characterized by highest conduction velocity (100m/s)
-large fiber diameters dictate fast conduction velocities.
-Innervates fast twitch muscle fibers.
2. Fast twitch, fatigue resistant (FR)
-60m/s medium velocity
-innervates fast twitch and slow twitch.
3. Slow twitch muscle fibers,
-slowest conduction time, 40m/s
Motor unit and Muscle Fiber Types in Athletes
-Red areas dictate more blood (heam) in one area and mean that they have
more oxygen or iron being given to them.
-lighter areas are fast twitch area
-paraplegics are not able to sustain long lasting movements.
-plasticity is existent in motor unit types.
-older adults primarily have slow twitch muscle fibers (difference between
younger adults and older adults falling).
-Postural stability can be increased by increasing fast twitch ratio (training).
-Dave Kosia’study found that wobble boarding training that 6 week training
in older adults can give an increase in fast twitch ratio, which gave an
improvement in overall balance.
-The types of neurons associated with motor cool are motor units (efferent
neurons) and sensory (afferent) neurons and the interneuron. The motor
neurons are specified to send messages away from the Central Nervous
System. The sensory neurons are specified in the senses of taste, touch,
hearing, smell, and sight. They send messages from the sensory receptors to
the Central Nervous System. The inter neurons are sort of a mix of both a
sensory neuron and a motor neuron.
-The Henneman principle states that recruit of motor units within a muscle proceed
from small motor units to large ones.
-Nearly all force is completed by the slowest motor units.
-When contraction increases larger units begin to fire.
-At the highest level of force the most powerful motor units are fired.
-neuropsychological studies are for evaluating behavioral tasks.
-ERP, event related brain potential
-Measured by EEG (Electroencephalograph, which measures electrical activation of the
cortex, which is essentially measuring neuronal activation. -By exposing someone to stimuli, one can observe how the brain is reacting to the
-The N2PC is a related brain potential that measures visual spatial potential
-P300 is a related brain potential that signifies if one is poor at classifying stimuli or
information (opposing player versus team mate).
-Deveaumont study, athletes with single concussion, athletes with no concussion,
and athletes with 2 or more concussions (9 months removed from concussions).
-No group differed in results on the impact battery, meaning that everyone had the
same neuropsychological capacity.
-Participants had to classify a target and classify an appropriate response.
-The speed of decision-making was the same across the three groups.
-The amplitude of their response decreased as a function of the frequency of the
-This study shows that there is a difference in the neurophysiological and
neuropsychological potential in concussed athletes.
-Neurons are not firing effectively.
-The specificity of the long-term effect of concussion provides a framework to
pinpoint the cognitive system impaired in multiple concussion.
-This is used to pin point the regions that may be the most susceptive to
-The impact battery is not the most precise method to detect whether someone is
-Top down decision is made when drawing gun, cortical activation present.
-Top down decision is a slow process because it involves multiple cortical regions
and results in slower response.
-In contrast to this, the person who views their opponent draw their gun has a visual
stimulus response that involves a basic neuro-circuitry. This circuitry is not cortical;
these responses are mediated sub cortically, in other words fast.
The Scientific Method
-Goals of science are to understand events; this involves describing, explaining, and
predicting these events.
-Empiricism is the process of verification by observation.
Science is a process of gathering knowledge about the world. This process is
understood by asking questions, making hypotheses about nature of things and
testing these hypotheses, and providing a systematic approach to understand this
process. Science is just one way of acquiring knowledge.
-The research of an experiment is used to determine whether the hypotheses are
true or false. It determines the nature of relationship between variables. -A manipulated variable is independent where a measured variable is dependent.
Any change as a result of the dependent variable is assumed to be a result of the
manipulated independent variable.
-For example an independent variable can involve visual and auditory signals and a
dependent variable be reaction time.
-When reading through an abstract…Be able to:
Identify independent and dependent variables.
How do these variables relate to the concepts of interests?
What are the experiment result(s)?
What are the interpretations/conclusions?
Classifying and Identifying Motor Skills.
-Taxonomy a way to make a classification.
-Taxonomies can be classified using task organization, motor and cognitive
elements, and level of environmental predictability.
-In a clinical perspective a subject should not be exposed to an objective that they
cannot yet perform properly. (Closed head injury)
-Task organization is classified by discrete skills, which have a brief skill and have a
beginning and end to the task(completing a dive). A serial skill is classified by serial
discrete actions, which are connected together in a sequence; the order of the
discrete elements is critical to task performance. An example of this is driving a
standard car. A continuous skill does not have a recognizable beginning or end and
have a repetitive action (swimming).
-A continuum has a discrete beginning end and continues end with a serial
classification in the middle between the two.
-Another classification motor skills is the motor cognitive continuum which
measures the quality of the skill.
-Young children do not have a developed cortex, as this progresses they become less
reliant on their cortical skills and more on their cerebellum.
-The third method of classification is classified under the level of environmental
An open skill is conducted in an unpredictable or in motion environment requiring
individuals to adopt their movement in responses to their environment. This can
reduce the risk of falling in people who may for example have an injury to their legs.
-A closed skill is conducted in a stationary or predictable environment and can
therefore plan their movement in advance.
Measurement, Interpretation and Evaluation of Motor Skill Performance
-Reaction represents the interval between a stimulus and an initiation of a response.
This is measuring the speed at which a stimulus can be detected and the processing
time that is needed to initiate a movement (response programming).
-Reaction time is divided into three categories, these being:
Simple Reaction Time Choice Reaction Time
Discriminant Reaction Time
-Reaction time tasks: Simple reaction time, which starts with a warning signal, and a
go signal. The period of time between the go signal and the movement starting is the
reaction time. The interval between the starting of the movement and ending of the
movement is the movement time. This is not related to reaction time. Reaction
time+movement time=total response time.
-The foreperiod is the time between the warning sign and the go signal; the
foreperiod is varied in order to eliminate anticipation.
-Choice reaction time is longer than a simple reaction time because identification of
stimuli is used as well as a cognitive decision as to which response is linked to the
stimulus. This involves top down cognitive choices in the frontal lobe.
-Discriminant reaction is referred to as a go no go paradigm. Multiple stimuli are
used, however only one response is used. For example there may not be any
response associated with the stimuli. This involves the inhibition of the response.
-Fractionated reaction time is divided into two components:
Premotor Reaction time, which is the onset of the stimulus to the onset of the
muscle activation. This involves EMG. Pre motor RT is providing someone
with an index that shows the processing time to plan and program a
Motor RT measures the time that movement time begins. It reflects an electro
mechanical delay that is associated with the lag muscle to overcome inertia
of the limb.
-Electromyography shows the differences between premotor time and motor
time. Motor time shows increased EMG activation. Activation in the motor
time is the build up in extrafusels, there is no movement in this period of
-A person with Alzheimer’s will have a prolonged premotor reaction time.
-An individual with a permeated disc will have a prolonged motor time due
to the muscle have delayed activation.
-EMG is also used to make diagnosis in mechanical delays.
-An anticipated start in sprinting for example is different than a reaction
-A pure measure of anticipation could eliminate a bias in anticipation or a
-Movement time is the time a response is made. Difference between initiation
and completion of a movement.
-Describing a movement is through the use of kinematics which describes
pure motion as well as how far and how fast it. It is broken down by…. -Displacement is the special position of effector during movement.
-Velocity is that rate of change of an objects position with respect to
-Acceleration is the change of velocity during movement.
-The displacement of human limbs is not linear; humans like to move in a
slightly curved linear fashion. This is a good example of increased visual
control due to the ability to recognize limb of movement in comparison to an
-A velocity profile is of a bell shaped fashion, however slightly positively
skewed. This signifies smooth movement (bell shape). This ballistic
movement was programmed fast and cannot be regulated by feedback
structures. Once peak velocity is reached the movement is slowed down and
feedback can be used to modify the movement. The time after peak velocity is
slightly longer due to this feedback. The peak of velocity scales with the
amplitude of response.
-Acceleration looks similar to velocity, however the peak of acceleration and
deceleration are scaled to movement distance. Smooth acceleration profiles
signify an optimized movement skill.
-A strong relationship between wrist and elbow velocity should be present in
a normal individual. An error in this is a time problem between the
coordination between multiple effectors, essentially moving all effectors
independently and not in a coordinated fashion.
-Characteristic and phasic activation are measured during EMG, which
determines which extra fusels are firing and how long they are being fired
-A tonic activation (synchronous) is an artificial stimulation of a muscle
(electrical or magnetic stimulation.) This is different from a phasic activation,
which is a voluntary activation of a muscle. These look different because the
extrafeusals activate at the same time during a tonic
activation(Characteristic). In a phasic activation (asynchronous), different
motor neuron pools will not overlap and fire at different times. Tonic pattern
activations can only be elicited in a lab.
-Clasp knife rigidity is a clinical sign of an upper motor neuron injury. This
usually happens to large effector muscles.
-A victim of a closed head injury in a motor neuron injury is first tested in a
sit to stand movement. This victim is subject to a contraction of their
-Trans cranial magnetic stimulation is used to create virtual lesions. Putting a
coil places overhead that sends single pulse to brain that causes neurons in
that area. (One pulse) ***The higher resolution in neuron projection, the higher ability to project an
Repetitive trans cranial magnetic stimulation is used to relive patients who
suffer from depression. (multiple pulse)
Singing is lateralized to the right hemisphere.
-TMS study to measure excitability with motor imagery, essentially
measuring cortical spinal activity. EMG is combined with TMS to measure
-A motor evoked potential (MEP), measured by EMG.
-Fadiga wanted to look at the MEP’s associated with the motor task. The
elbow extensors and flexors were looked at in this study. When people were
told not to move and hand not moving they still recruit muscle activity like
they were going to move. This was in response to seeing an MEP being
-Motor imagery and physical practice entail the same cortical activation.
People can get better at a task simply by thinking about a task.
A study using RTMS was given to the V1 of a patient with congenital
blindness, and two others with blindness not associated with birth. In this
study LP was given a sense of parastisa in his fingertips, the others felt this as
well however not as much as LP. LP has been reading brail for a long time,
meaning his occipital lobe has portions devoted to haptic information.
RTMs is used to rehabilitate stroke patients through establishing a paradigm
that turns up or turns down the background activity associated with a
hemisphere. By turning down the activity in one hemisphere to reestablish
the equilibrium in the two hemispheres giving the effected hemisphere.
Another way is to turn up the effected hemisphere, this also establishes
-Sham condition is where a patient thinks they are receiving RTMS. The other
group was given 1 hertz or 5 hertz (effected hemisphere, to reestablish
equilibrium). Individuals with 1 hertz over unaffected hemisphere had the
best outcome. This shows that it can have long-term benefit to stroke
-RTMs can also help improve results associated with visual spacial neglect
-EEG and MEG are used to detect when an axon is being fired. They provide
exceptional temporal brain resolution (millisecond level).
-The limitation with these techniques is that they have poor special
resolution. -Brighter the area the higher activation, darker color represents deactivation.
-Research involved timing are involved with EEG and MEG
-Difference between MRI is a structural scan where an FMRI provides an
integration of function and structure through high spacial resolution. FMRI
has poor temporal resolution that an MRI does.
-AN FMRI provides high spacial resolution.
-PET scanning is used through the use of a radioactive isotope that looks at
metabolism in the brain. What parts of the brain are active during rest or
task? ---Brain needing oxygen, blood with isotope goes to area and isotope is
-Authors of concussion picked 5-football teams and filmed games. They
looked at the number of times an athlete had head hits. None that they
evaluated had a concussion. This study measured the S1000v protein in the
blood. This protein is found in the blood when there is trauma to the brain
blood barrier. This can cause an auto immune response, which can lead to a
long-term cognitive consequence. A simple blood test can now determine
whether somebody will be at a cognitive risk in contact sports. This protein
attacks the cortex.
-This can be linked to structural determination of the brain. Diffusion
tensoring imaging, provides a measure of axon connectivity.
-Womens soccer has the highest incidence of concussions than any other
sports. There is a strong belief that women are not meant to withstand
concussions as easily as men to.
-A cognitive information processing approach involves a three-stage process.
This includes, stimulus identification, response selection, and response
programming. This model proposes that each stage is linked to a serial
discrete action. These three processes cannot occur in a parallel fashion.
-Stimulus detection is about sensory reactors becoming active to an external
source and is put into raw neurological code. This stage happens below the
level of ones consciousness.
-Pattern recognition involves an environmental stimulus that is used in the
fore ladders of environmental stimulation. Training in pattern recognition
can optimize performance in a sport or any occupation. Peyton Manning
studies film replays to understand patterns to execute better responses in
the future. -Chess can demonstrate pattern recognition as well. Chase and Simon had
three groups, people who don’t play chess, amateurs, and chess masters.
They were curious to see who had the best pattern recognition. Chess pieces
were removed and had to recall where pieces were. Chess masters were the
best in terms of pattern recognition.
-Secondly, pieces were placed in an order that the pieces could not be placed
in a real game situation. The chess masters showed the worst performance in
-People who have reached a high level of expertise have dedicated ten years
and/or 10 000 hours of deliberate hours to their specific domain. Deliberate
practice is demanding. Anders Ericson states that anybody can reach an
expertise in a domain if they dedicate ten years and/or 10 000 hours of
-A study that involves medical students and physicians. This study was
conducted by showing the medical students and physicians study x-rays of
the ankle and were asked to make a diagnosis.
-the results had shown that the medical students had not done an exceptional
job at making diagnosis. The radiologist made accurate diagnosis. The
radiologists made an immediate diagnosis. This demonstrates that the
physician has 10 years or ten thousand hours of experience.
Starks- was interested in asymmetries were present in the birth month and
expertise level. She looked at the month of which hockey players were born
and separated them into quartiles. She looked at frequencies and such as
OHL and NHL to house league. The same thing was done in Italy in terms of
soccer. Almost 50 percent of highest skilled athletes were born in the first
quartile. In the second league, individuals from the general population league
showed no asymmetries in the quartiles.
-Maturation and coaching can be the reason to this. With this, they are able to
devote the necessary deliberate practice needed to develop expertise for that
-Response stimulus is the most well studied stage out of this process. The
number of stimulus response alternatives as well as spacial or cognitive
compatibility. Hick and Hymen conducted a study using choice reaction time
protocols was used. This law states that as the stimulus response alternatives
there is an increase in reaction time of approximately 150m/s. Hick and
Hymen were able to establish a logarithm to predict possible reactions times.
There is a linear increase in reaction time as a function of nits of information.
This information can be modeled by using an equation for a straight line.
-When someone behavior can be predicted, a researcher can produce an
interface and predict behavior. -The index of difficulty provides us with how much information is being
processed. N represents stimulus response alternatives. A bit of information
is reducing uncertainty by ½. By reducing uncertainty by ½ once again, they
are processing another bit of information.
-The change of reaction time in a unit of information is determined by slope.
The slope is also age specific, for instance young adults have a very moderate
slope where older adults have a steeper slope. This is because older adults
may have fewer connections in their brain; they also take longer to process
information. A computer analogy best describes why older people take
longer in terms of reaction time, for example from a hardware standpoint, is
the degrading neuro connections impede the effectiveness of the CNS. From a
software standpoint, older adults selectively decide to move slower to make
a correct response. Most researchers will say that it is a combination of two
-The more practice one has of a task, the shallower the slope will be because
they will be able to process information quicker. The slope of Hick Hymens
equation is going to be effected by the effector that is used. For example the
difference between hands and eyes is twenty ms where as hands and feet
could be 50 ms.
-An idea of spacial compatibility was brought up by Paul Fitz, he was
interested in stimulus response compatibility specifically between spacial
compatibility between a stimulus and a response. Reaction time is
lengthened when there is a lack of compatibility between stimulus and
response. Many accidents were happening because designers did not have an
appreciation for human’s natural spacial compatibility. A lack of spacial
compatibility results in a delayed response or accuracy in the response.
-The dorsal lateral prefrontal cortex must be involved when there is thought
about a decision or top down cognitive control. This area has a lot of
processing power, however it takes lots of time to process this area.
The final stage of this three-stage model, is the response programming stage.
Movement complexity was increased in Henry and Rogers study. The more
complex movements showed an increase in reaction time. People are actually
planning their movements prior to responding. Prior to this, most
researchers believed that responses were planned on the spot.
-Henry and Rogers found that people have a package of motor commands
that tell us how to move.
Topic #7 Attention
-Attention is defined as focalization and limitation of information processing
resources (Schmidt and Wrisberg). This states that one must be aware for
one to attend to it, which is not fully accurate. Attention and consciousness
are not specifically tied to one another. -Reinesser conducted a study to conduct whether consciousness and
attention were connected to one another. They were presented 100 words
where 25 words were paired with mild electrical stimulus. He did this twice,
once in the fall and once in the spring. Where 75 words were new and 25
were the same from the last experiment. He measured galvanic skin response
which provides a measure of skin conductance. He found that the words from
before elicited a high GSR conductance, in other words they were not
conscious that they were the words from before, however they were
attentive, meaning their attention system was working below the threshold
of their consciousness.
-Change blindness states that people can detect stimulus well if there is a
change to our environment, a dynamic and unexpected visual stimulus is
hardwired to our central nervous system. Sometimes when things are slow,
we do not attend to a change. People only have so much attention at one time
and cannot use it for things we cannot see.
-A prime example of this is how people talk on the phone while driving.
Exceeding attention demand can result in accidents. Speaking with someone
in a car is less dangerous than talking with somebody on the phone while
driving a car. Passengers are interactive with you where people talking on
cell phones are not.
-Broadbent proposed a model of attention that was an early model of
attention (3 channel approach). At stimulus identification, there is a
bottleneck, which stipulates only one channel of information can be
processed at this stage. (Conversation at cocktail party, other channels of
information). At some level however, one must be able to process more than
one channel of information.
-As a result, Broadbends theory has been changed to a more modern model
of attention. Proposed by Norment, it states that multiple channels are
available in the stimulus identification, however response selection and
response execution are limited to one channel.
-The psychological refractory period basically states that once on stimulus
has been triggered another cannot be triggered once it has finished.
In a lab-based experiment, there are two stimuli that are used. The reaction
time in the first experiment’s reaction time is not influenced by the second
stimuli. However the second response is influenced by the first stimuli,
therefore resulting in a delay in reaction time. The delay is thought to occur
at the response selection stage. The proximity between stimulus 1 and
stimulus 2 are very close to one another. There is no psychological refractory
period between 0 and 50 ms, this is because they are processed as a single
stimulus. Psychological refractoriness takes large impact at 110 ms.
Psychological refractoriness is the highest at around 55ms. -Different pools of attention are present that are specific to different verbal,
spatial, and cognitive and motor capabilities. These can be completed at the
same time because they are not part of the same pool of attention. Baddley
developed the multiple resource theory of attention because tasks can only
be occurring in one of the resources and only have one task occur in each
-The Veissman study conducted local and global decisions about a stimulus. A
local decision is where all stimuli are composed together, a local feature is
one stimuli. There is a congruent situation (S and s), and an incongruent
situation (S and e). A local classification of an incongruent stimuli involves
numerous mistakes, which results in an attention slip. When people make an
action slip the right Inferior frontal gyrus (IFG) is not active, when people
make right classifications, then the right IFG is firing rapidly. Veissman