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The following study examines the effects of positive visualization on strength training. Positive visualization is being defined as: visualizing yourself performing a physical movement to best of your capability or beyond. Student-athletes were asked to positively visualize themselves performing lifts that they physically executed frequently in their training regimen (bench-press, back squat, clean or deadlift). A directionality analysis demonstrated that, compared to athletes who did not, participants who positively visualized had a significant increase in weight moved during a lift. The positively visualizing group demonstrated a 10-15 lb. increase in weight moved, while the control group only demonstrated a 5 lb. increase. This suggests that athletes are more successful when incorporating positive visualization into their training. Power movements (clean) dramatically increased, suggesting a follow-up study specific to type of muscle development and movement, could further improve the efficiency of athletic training combined with visualization. This research is important to the field of neurophysiology, as it demonstrates a connection between the mind (visualization) promoting potential change in neural circuity and muscle development (measured by strength). If we are better able to understand how thought and visualization influence the brain and the nervous system, we might be better equipped to understand the mind-body connection, and utilize it to promote health and wellness.
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Impulse: The Premier Undergraduate Neuroscience Journal
Positive Visualization and Its Effects on Strength Training
Janette Hynes, Zach Turner
Transylvania University, Lexington, KY, United States, 40508
The following study examines the effects of positive visualization on strength training. Positive
visualization is being defined as: visualizing yourself performing a physical movement to best of
your capability or beyond. Student-athletes were asked to positively visualize themselves
performing lifts that they physically executed frequently in their training regimen (bench-press,
back squat, clean or deadlift). A directionality analysis demonstrated that, compared to athletes
who did not, participants who positively visualized had a significant increase in weight moved
during a lift. The positively visualizing group demonstrated a 10-15 lb. increase in weight moved,
while the control group only demonstrated a 5 lb. increase. This suggests that athletes are more
successful when incorporating positive visualization into their training. Power movements (clean)
dramatically increased, suggesting a follow-up study specific to type of muscle development and
movement, could further improve the efficiency of athletic training combined with visualization.
This research is important to the field of neurophysiology, as it demonstrates a connection between
the mind (visualization) promoting potential change in neural circuity and muscle development
(measured by strength). If we are better able to understand how thought and visualization influence
the brain and the nervous system, we might be better equipped to understand the mind-body
connection, and utilize it to promote health and wellness.
Keywords: Positive visualization, strength regimen, muscular development, neuropsychology
In Norman Doidge’s book, The Brain that
Changes Itself, he discusses the idea of
visualization (imaging yourself doing something
involving physical movement) and how it can
physically change our minds and bodies (Doidge,
2007). He illustrates an experiment where
“physical exercise” increased muscle strength by
30% while “imagined exercised” increased
muscle strength by 22% (Clark, Mahato,
Nakazawa, Law, & Thomas, 2014). Meaning,
without any physical activity,
visualization/imagery alone could increase
muscle strength thus producing a physical change
within the body. Visualization has also been
proven to enhance athletic tasks and musical
performance and skill (Driskell, Copper, &
Moran, 1994). Driskell and colleagues illustrated
that visualization can improve how neurons
respond to stimulus, and therefore improve the
efficiency of body movement during a specific
Just as moving a body part would activate
certain cortical areas, mental imagery has been
shown to activate several cortical areas that are
involved with actual motor behaviors (Clark et
al., 2014). Meaning, there is a relationship
between cortex and strength development. Just as
performing a movement develops muscle
memory, actively visualizing a movement can
also improve muscle efficiency during a task
(Ranganath, Vlodek Siemionow, Jing Liu, 2004).
These two sources suggest that athletes who
visualize themselves completing a repetition of a
given movement may be able to develop strength
and efficiency without ever actually physically
performing it. Research shows a relationship
between an increase in muscular strength and
neural adaptions as well (Carroll, 2012). So, as
athletes visualized themselves completing a
repetition and created a neural adaption, they may
also increase their muscular strength
simultaneously. This would help explain why the
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Positive Visualization and Strength Training
act of visualization can directly increase
muscular strength, as they seem to be functioning
as one system (or at least participate in a
mutualistic relationship). In corroboration,
studies have also proven that if a particular body
part becomes immobile, corresponding cerebral
cortex area input will decrease (Kaneko,
Murakami, Onari, Kurumadani, & Kawaguchi,
2003). Meaning, when a body part is no longer
active, part of the brain becomes less active as
well. This suggests that by visualizing the
movement of the specific immobilized body part,
the area of the cerebral cortex would remain
active in some way, and recovery of movement
may be more successful. This is further evidence
to our claim that through athletes positively
visualizing they will be able to further increase
their strength than if they simply physically
performed the movements.
Neurotransmitters and Axon Development
Certain neurotransmitters encourage the
development of axon pathways. Research has
illustrated that in Drosophila embryos,
neuromuscular junctions are formed selectively
by motoneurons (Johansen, Halpern, &
Keshishian, 1989). This research may suggest
that if athletes visualize themselves performing
the movements and stimulate motoneurons,
neuromuscular junctions may be more likely to
form which would increase strength and
efficiency. For example, research has
demonstrated that acetylcholine receptors
(AChRs) accumulated within muscle fibers,
exactly where synapses eventually form (Jing, et
al., 2008). Cholinergic activity manipulation
through imagery has been shown in empirical
research analyzing humans (Ishii, et al., 2013). If
mental imagery has the potential to produce
cholinergic effects physiologically, then perhaps
synapse formation will be further guided through
mental visualization.
Furthermore, the development of new axon
pathways can benefit nerve regeneration, and also
encourage plasticity of the brain (Skene, 1989).
From this research, it may be theorized that
through neurotransmitters encouraging new axon
pathways, the brain is more likely to change and
therefore increase the potential for physical and
mental development of the athlete.
Muscle Activation and Neurotransmitters
A muscle is voluntarily activated when force
is produced by the recruitment of motoneurons
through a chemical signal from the motor cortex.
This activation is usually conscious and
deliberate. This conscious act requires the subject
to exert effort in order for the act to be completed.
Influences that impact voluntary activation
include excitatory and inhibitory sensory
information that may make them responsive to
synaptic input. Voluntary activation reflects the
nervous system's ability to fully activate muscle
and is assessed by electrically stimulating a
peripheral nerve during a maximal voluntary
contraction and telling the “added force” (Taylor,
2009). Essentially, voluntary activation requires
deliberate force, and this deliberation is
motivated by a neurotransmitter(s) responding to
a stimulus. In this way, neural activity produces
muscular activity.
Therefore, through athletes actively
stimulating their neural system through
visualization, they may improve their ability to
activate muscles via motoneurons and motor
units. This would be extremely beneficial in
strength training, as it would allow for full use of
the muscles being recruited, and also increase the
maximal force produced. In a way, visualization
may provide a practice stimulus for the neural
system, and allow it to rehearse activating
muscles at some level. Empirical research has
demonstrated through EMG, that when imaging
lifting a particular weight (heavy, moderate, or
light) the brain responds in the same activation
level (or effort) as if the athlete were physically
lifting the desired weight (Guillot, et al., 2007).
This research specifically looked at 9 muscles
within the arm being used to move the weight,
and found neural firing within related brain
regions for these muscles and their motor units.
Strength and Neural Training
Strength is impacted by multiple variables.
For instance, research has suggested that the
nervous system is also a factor of strength
exertion and development (Carroll, 2012). It may
be inferred from this research that the brain plays
a crucial role in strength performance and
development, therefore making it equally
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important for athletes to train mentally along with
physically. It has also been suggested that neural
training and strength training interact as sort of a
cross-education (Moritani & DeVries, 1979).
Research such as this further suggests that
training the mind is just as important as
physically training. Visualization may be an
excellent solution to athletes who aspire to
achieve this dual training. To expand, just as
unilateral training may increase strength in an
untrained body part, neural training may increase
strength in body parts that are not being
specifically trained physically, or increase
strength more than just physical training alone. In
this way, the body can be primed to complete the
process of chemical signal from cortex to muscle
performing the desired act, through visualizing
the act (Rm, Pm, & Ja, 2001). We may infer from
this knowledge, that visualization may aid to
prime the cortex to more efficiently perform
during strength exertion, and may lead to strength
development as seen with the unilateral training.
Present Study
The purpose of the present study is to observe
the effects of positive visualization on strength
development, and answer the questions: if an
athlete positively visualizes themselves lifting
weights, will they become stronger faster than an
athlete who does not visualize? If so, what is the
most successful duration of visualization, and
what lifts are most benefited? These questions are
important, as their answers could lead to more
efficient strength training, and could be crucial to
strength development in humans in general. If
athletes are able to build strength more quickly,
they are at a greater advantage to perform at a
higher level. Furthermore, this research may also
lead to further evidence of the brain’s
involvement in muscle development and
activation, and allow for further research
involving the brain and its relationship to the
constantly evolving body.
We predicted a correlation between
visualization and an increase in strength, as well
as a relationship between duration of
visualization and amount of strength increase.
Therefore, we predicted a directionality model.
Following the suggestions outlined, variable A
(positive visualization) is correlated with an
increase in variable B (strength).
Materials and Methods
133 participants (70 females and 63 males)
who participated in the strength and conditioning
program at Transylvania University were
recruited to participate in the study. Participants
ranged in age of 18-22 years with the average
being 20 years. Thirty-two of the participants
were black, seventy-eight were white, and
twenty-three were hispanic/latino. As an
incentive, participants were informed that proper
execution of positive visualization may improve
their strength and therefore their sport
performance. Each researcher has completion of
NIH training (Protecting Human Research
Participants), and received IRB approval for the
present study, in order to work with human
Design and Procedure
Participants were randomly selected from
eight Transylvania University athletic teams that
participated in the strength and conditioning
program. Participants were eligible to participate
if they were required to attend the strength and
conditioning program by their coach (to ensure
participation daily). An almost equal number of
females and males were drawn by using a
stratified sample.
Participants had backgrounds in
baseball, softball, basketball, soccer, lacrosse and
dance. Each sport had male and female teams
(and both were to utilized), except for dance (all
female) and lacrosse (only male team). Some
athletes reported also training additionally
(outside of the training program), in the likes of
running and machine-work. The majority
reported only working-out during the prescribed
training time in the weight room.
Participants completed an informed consent
which informed them of the possible risks and
benefits of completing the present study.
Participants were randomly assigned to groups
(control or test). If in the test group, participants
were asked to positively visualize themselves
performing a lift (lifting heavier weights than
normally possible; moving better/more
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Positive Visualization and Strength Training
efficiently during the lift; winning a competition
by performing a certain lift at a heavy enough
weight). If in the control group, participants were
not told to visualize, but rather to continue with
training as usual. Both groups consisted of
participants training in deadlift, bench-press,
clean or back-squat with varying frequency.
During the beginning of the strength and
conditioning program athletes were asked to
attempt a max lift (the type of lift was dependent
on sport and season). Participants then rated their
strength increase, and frequency/duration of
positive visualization (if in the test group), after a
three-week period. Both groups rated their
strength increase based on their initial max lift
(greatest weight that could possibly be completed
on a single repetition of a lift) at the beginning of
the three weeks, versus their max lift at the end of
the three weeks.
In order to positively visualize, athletes were
given a suggested recommendation ideal for
maximum concentration and consistency. It was
recommended that athletes choose a specific time
of day to visualize, and attempt to keep that
appointment as consistently as possible to
eliminate outside factors. It was recommended
that athletes lie down in a quiet area free of
distractions, and listen to motivational music if
they found that helpful before physical
performance (to help create a training mindset,
many athletes have particular songs they find
motivating and helpful in focusing).
Athletes could choose how frequently they
visualized, and for how long they visualized as
long as it was at least 5 minutes. It was suggested
that athletes visualize themselves lifting at
around 110% of their one rep max. For example,
if an athlete deadlifted 300 lbs, they would
visualize themselves deadlifting 330 lbs. It was
emphasized that athletes should try to visualize
themselves performing the movement as
efficiently as possible (fast, good form,
confident), and attempt to visualize what it would
feel like to actually physically perform the
At the end of the study, athletes were
debriefed on the results of the present study.
Control and experimental groups were explained,
and the assignment of each athlete to which group
was revealed to ensure each participant
understood how they had participated. It was also
made clear to the control group, that while they
had not demonstrated as great of an improvement
in strength, there was never any variable working
against their improvement in this study.
Furthermore, based on the results, athletes were
all encouraged to positively visualize regardless
of which group they had previously been a part
Experimental Materials
Additional materials included a training room
with standard equipment (barbells, bumper
plates, clips, belts). All athletes performed their
lifts on 45 lb. Rogue training bars, with bumper
plates and clips to secure the weight loaded.
Athletes all lifted on cushioned rubber mats and
were allowed to wear their preferred lifting shoes.
Athletes were also allowed to use weight-belts to
help prevent injury if they chose to do so. All of
the equipment was provided by the Transylvania
University Strength and Conditioning Program.
For measuring strength improvement,
participants completed a survey at the end of the
experimental trial. The survey consisted of three
closed-ended questions that were ranked on a
five-point-scale and two additional close-ended
questions. Participants ranked their improvement
in pounds added to lift (1 = none, 5 = 15+
pounds), their frequency of positive visualization
(1 = never, 5 = 7+ times a week) and duration of
visualization (1 = less than 5 minutes, 5 = 20+
minutes). Participants were also asked to identify
the type of lift (deadlift, clean, back-squat or
bench-press) and how many times a week it was
trained (twice or three times a week).
Statistical Analysis
Statistical analyses were conducted using R
(build version 1.66 Snow Leopard build) and R
Studio “build version 1.0.153.” In order to assess
the difference of means between groups of
athletes who positively visualized and those who
did not, a t-test was calculated. To decide which
statistical test was most appropriate for the given
data, tests of normality were performed.
The Shapiro-Wilk test calculated normal
distribution of data (Table 1), while the Levene’s
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test for equality of variance found unequal
variance (Table 2). Due to these circumstances
and assumptions, a Welch t-test was calculated in
order to analyze the means of the two groups. The
Welch t-test (Table 2) was run with a 95%
confidence interval (CI) for the mean difference.
Table 1.
The Shapiro-Wilk Test
Note. The null hypothesis can be rejected (p>0.05) and the
data is normally distributed.
Table 2. The Welch’s t-test and Levene’s Test for
Equality of Variance.
Note. The Levene’s test for equality of variance calculated
that the requirement for homogeneity was not met.
Therefore, a Welch t-test was performed to account for the
unequal variance between groups.
Figure 1 Mean increase in strength influenced by duration
of visualization. The y-axis represents the weight added to
the lift by the end of the study. The x-axis represents the
duration of positive visualization in minutes. Error bars
represent standard error.
Lifts and Muscle Recruitment
As seen in Fig. 2, each lift demonstrated
different increases in strength. In order to further
analyze the results of the present study, the
muscles used in each lift were considered for
strength increase.
In both groups, the deadlift saw the lowest
increase in strength. Because both groups
demonstrated a lower increase, it can be theorized
that the erector spinae, gluteus maximus, and
hamstrings (the main muscles used for the
deadlift) may take longer to develop strength.
Because both groups demonstrated a lower
increase, it can be theorized that the erector
spinae, gluteus maximus, and hamstrings (the
main muscles used for the deadlift) may take
longer to develop strength.
Figure 2. Mean increase in strength per lift and group. The
Y-axis represents the strength increase, and the X-axis
represents the four lifts and group assignment. The blue bars
illustrate the test-group results, while the orange bars
illustrate the control group results. Error bars represent
standard error.
The back-squat was the highest average in
strength increase in the control group. This means
that athletes who didn’t visualize had most
success in the back squat, while athletes who did
only saw some increase (on average 5 lb. more
than the control group) compared to the increase
in other lifts. The main muscles used during a
back squat are the upper back, abdominals,
lumbar spine, gluteals, thigh adductors,
quadriceps, hamstrings, and calves. Clearly, a
large number of muscles are activated to perform
the lift, and it could be theorized that this could
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Figure 3. Demonstration of the power clean. The lift begins from the floor with the athlete preparing to pull (panel 1). Next, the
athlete pulls the bar to hip level (panel 2-3) while simultaneously using an aggressive thrust of the hips (panel 3) to further the
trajectory of the barbell upward. After the hips and legs have driven the barbell upward, the athlete uses their arms to finish pulling
to their fullest extent (panel 4). The receiving position of the barbell is above parallel (not in a squat) with the elbows high in the
front rack position (panel 5). Lastly, the athlete stands the barbell all the way up to a standing position (panel 6).
limit the ability of visualization to increase
strength. Essentially, the higher the number of
muscle groups used to perform a movement, the
less likely that visualizing will condition the mind
to activate all the necessary muscles.
The clean illustrated the greatest increase in
strength, averaging at a 15 lb. increase. The group
of athletes performing cleans did so in the power
style. The lift does not include a squat, rather a
pull and hip-pop which guides the barbell to the
chest/collar bone without the hips dropping
below the knee. This movement requires
explosive movement and speed, which activates
the shoulders and posterior chain. The lift is
shown in Figure 3. Because such a high increase
in weight moved was seen, it might be argued that
visualization was most successful in increasing
explosiveness and speed (even with a higher
number of muscles being activated). Further
research is needed to test this hypothesis, as speed
and explosiveness were not a measure in the
present study.
Interestingly enough, the power clean mimics
the deadlift in the first part of the lift. The fact that
athletes saw limited strength increase in the
deadlift, but saw a tremendous increase in the
power clean, suggests that athletes are
approaching the lifts with different mindsets.
While some athletes focus on the speed of the bar
and moving fast, some may be focusing on
simply completing the lift. I would theorize that
if athletes approached the deadlift with the same
speed/explosive mindset that they did the power
clean, they would see an increase in the deadlift
as well. Perhaps when athletes focus more on
speed rather than strength alone, more muscle
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recruitment and motor unit activation occur and
thus there is more potential to activate these
afferent and efferent pathways when visualizing.
Lastly, the bench-press also demonstrated a
large increase in strength, particularly in the test-
group. Readers can explore the execution of all of
the lifts examined in this research at many web
sites dedicated to fitness or weight lifting.
“StrongLifts” (
provides particularly good examples.
On average, participants in the test-group
averaged a 10 lb. increase in their lift versus the
control which saw an average of 5 lb. increase.
The muscle groups recruited include (but are not
restricted to) the pectorals (minor and major),
bicep brachii, and deltoid. These muscle groups
are smaller in size, and may be more susceptible
to positive-visualization based on the results seen
in this study.
The purpose of this study was to examine the
influence of positive visualization on strength
development in collegiate athletes. Considering
the athletes who visualized, we predicted and
found, that participants who positively visualized
along with their training correlated with a larger
increase in strength than those who did not
visualize. Participants who visualized with their
training demonstrated greater strength gain and
proficiency in their regimen. Furthermore, we
predicted that there would be specific durations
of visualization that would be most potent in
developing strength. Based on the present study
data, this duration is within 5-15 minutes, and
produces about a 10 lbs. increase. In
corroboration, we also predicted that
visualization would have a greater effect on
certain lifts. As illustrated in the present study,
power lifts increased the most substantially.
Duration of Visualization Impact
Based on the results of the present study, a
trend can be observed in the increase of
visualization and increase in strength (Fig. 1).
Positively visualizing is correlated with increased
weight moved for back squat, bench press, clean,
and deadlift (Fig. 2), compared to the results of
the control group.
Based on the data, visualizing between 5-15
minutes will produce similar results, but 15 or
more minutes produces a greater increase in
strength. There is a greater increase in strength of
athletes who positively visualized compared to
those who don’t (Figures 1 and 2). Athletes who
visualized demonstrated increase in strength (on
average seeing 10-15 lb. increase) compared to
those athletes in the control group (on average
seeing only a 5 lb. increase). It can be theorized
that those participants who visualized for over
fifteen minutes allowed more time for developing
new axon pathways within the brain. This also
highlights the importance of time on the
efficiency of visualization and its involvement in
strength development.
Furthermore, statistical analysis found that the
athletes who coupled positive visualization with
strength training (11.417 ± 0.461) demonstrated
a significantly greater an increase in strength than
athletes who only performed strength training
(5.513 ± 0.432) (t(128) = 10.133, p < .05) with a
difference of 6.26 (95% CI, -7.48 to -5.04)
pounds added (measured in weight moved on
testing lift) (table 2).
Because the present study suggests that
athletes who positively visualize have a greater
improvement in strength than those who do not,
it might be argued that these athletes who
visualize are improving their neuromuscular
junctions are axon development. As discussed
previously, cholinergic activation has been
shown to occur due to imagery in human
participants, and ACh in particular has been
demonstrated to help guide synapse and axon
formation between motor units and the muscle
fibers. If this is the case, and these athletes are
able to stimulate a neurogenesis of sorts through
visualizing, they could potentially be increasing
efficiency between the desired muscle group(s)
and motor pathways within the brain.
Perhaps these athletes are not so much
building physical strength, but learning to move
more efficiently through priming the motor
pathways to function with the muscle fibers more
proficiently. However, by definition, strength is
the ability to exert force onto an object.
Therefore, through these athletes theoretically
being able to do so more proficiently, does also
suggest an argument for an increase in strength.
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Positive Visualization and Strength Training
Our research suggests that potentially more
adaptions in neurophysiology occur through
neural training, and that it is most beneficial to
physiological strength when coupled with
physical training.
The present study was limited in dependency
on participants to properly visualize and
physically perform the lifts. There being 133
participants, it was increasingly difficult to
ensure all were properly positively visualizing
themselves lift and doing so enough times during
the week. Some participants were also unable to
properly perform the lift physically,
compromising the visualization of the lift.
Research has already shown that physical
movement plays a large role in neurological well-
being (Smits-Engelsman & Van Galen, 1997), so
it can be theorized that if a participant cannot
physically move well, visualizing the movement
may not recruit the proper neurological pathways
to improve strength, or cause the proper
physiological responses such as a release of ACh.
To substantiate this claim, consider the effects the
brain can have on the body. Neuronal oscillations
control and contribute to a number of
physiological processes and neurophysiologists
have found
that misfiring neurons can lead to physical
tremors. Research has suggested that alterations
in neuronal firing rates underlie the spectrum of
movement disorders (Hutchison, 2004).
Essentially, by physically moving poorly during
a lift, the mind cannot develop new pathways to
increase strength or may develop less efficient
Furthermore, the collection of data for this
study was done through self-report. This creates
more potential for human-error regarding the data
for the present study (specifically, the duration of
visualization and frequency). Therefore, our
results cannot be said with certainty to be causal,
but rather only a correlation between neural
training and strength development. The ability to
generalize the results and apply their findings to
the general public is erroneous as there is not a
direct link of casualty.
Application and Theory
The empirical findings of this study suggest
that coupling positive visualization with strength
training regimens produces a greater increase in
strength than following a regimen without also
positively visualizing. In this particular study,
collegiate athletes were used for sampling, but
these findings could be beneficial to the general
population as well. In theory, these findings could
be applied to any individual who physically
Research has demonstrated that intrinsic
factors can predict exercise levels (Teixeira et al.,
2012). These researchers used the self-
determination theory to assess how likely
participants were to exercise and consistently do
so. The results suggest that the more positive the
internal state of an individual is, the more likely
they are to exercise and to continue doing so. The
present study may build on this research further,
through theorizing that positive visualization
increases the likelihood of a positive internal
state. If this is accepted, then through the general
population positively visualizing, there could
also be an increase in exercise frequency from the
general population. This increase in exercise
could also in theory aid in the prevention and
treatment of chronic diseases caused by lack of
motivation to exercise.
The present study has demonstrated that this
positive visualization also promotes a greater
increase in physical performance versus groups
that do not positively visualize. Therefore, the use
of positive visualization coupled with a training
regimen could not only promote an increase in
exercise frequency, but also in desired outcome
through bettering the likelihood of improvement
in strength. Therefore, the general population
may see better results from training, feel an
increase in motivation to continue their training
due to experiencing progress, and also see
important health benefits that are related to
consistent exercise.
Lastly, future directions for the present study
may analyze movements and muscle groups
specifically. The present study demonstrated that
power movements were most benefited by neural
training, imploring the question be asked why
this is the case. It may be beneficial to implement
a test group that only positively visualizes
without physical training. This would allow
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researchers to directly observe the effects of
neural training alone, specifically to muscle
growth. This could be used to answer if neural
training only increases efficiency of movement,
or if it has the potential to directly build strength.
The results of the present study support the
notion that positive visualization combined with
physical training produces a greater increase in
strength than physical training alone. While
research on visualization and strength
development often focuses on regaining strength
rather than building on it, we would argue that
more attention is needed on the interaction of
neurophysiology and physical strength growth.
Not only would it be a vital topic for collegiate
athletes, but for anyone looking for a more
efficient way to improve their physique and
health, and overall well-being.
Special thanks to Zachary Turner for his
collaboration on the present study, and to Dr. Iva
Katzarska-Miller for her guidance.
Corresponding Author
Janette Hynes
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We tested the hypothesis that the nervous system, and the cortex in particular, is a critical determinant of muscle strength/weakness and that a high level of corticospinal inhibition is an important neurophysiologic factor regulating force generation. A group of healthy individuals underwent 4-weeks of wrist-hand immobilization to induce weakness. Another group also underwent 4-weeks of immobilization, but they also performed mental imagery of strong muscle contractions five days/wk. Mental imagery has been shown to activate several cortical areas that are involved with actual motor behaviors- including premotor and M1 regions. A control group, who underwent no interventions, also participated in this study. Before, immediately after, and one-week following immobilization, we measured wrist flexor strength, VA, and the cortical silent period (SP; a measure that reflect corticospinal inhibition quantified via transcranial magnetic stimulation). Immobilization decreased strength 45.1±5.0%, impaired VA 23.2±5.8%, and prolonged the SP 13.5±2.6%. Mental imagery training, however, attenuated the loss of strength and VA by ~ 50% (23.8±5.6% and 12.9±3.2% reductions, respectively), and eliminated prolongation of the SP (4.8±2.8% reduction). Significant associations were observed between the changes in muscle strength and VA (r=0.56) and SP (r=-0.39). These findings suggest neurological mechanisms, most likely at the cortical level, contribute significantly to disuse-induced weakness, and that regular activation of the cortical regions via imagery attenuates weakness and VA by maintaining normal levels of inhibition.
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We have recently reported that central command contributes to increased blood flow in both noncontracting and contracting vastus lateralis (VL) muscles at the early period of voluntary one-legged cycling. The purpose of this study was to examine whether sympathetic cholinergic vasodilatation mediates the increases in blood flows of both muscles during one-legged exercise. Following intravenous administration of atropine (10 μg/kg), eight subjects performed voluntary 1-min one-legged cycling (at 35% of maximal voluntary effort) and mental imagery of the exercise. The relative concentrations of oxygenated- and deoxygenated-hemoglobin (Oxy- and Deoxy-Hb) in the bilateral VL were measured as an index of muscle tissue blood flow with near-infrared spectroscopy (NIRS). The Oxy-Hb in both noncontracting and contracting VL increased at the early period of one-legged cycling, whereas the Deoxy-Hb did not alter at that period. Atropine blunted (P < 0.05) the Oxy-Hb responses of both VL muscles but did not affect the Deoxy-Hb responses. The time course and magnitude of the atropine-sensitive component in the Oxy-Hb response were quite similar between the noncontracting and contracting VL muscles. With no changes in the Deoxy-Hb and hemodynamics, imagery of one-legged cycling induced the bilateral increases in the Oxy-Hb, which were completely abolished by atropine. In contrast, imagery of a circle (with no relation to exercise) did not alter the NIRS signals, irrespective of the presence or absence of atropine. It is concluded that central command evokes cholinergic vasodilatation equally in bilateral VL muscles during voluntary one-legged cycling and motor imagery.
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Chronic diseases are major killers in the modern era. Physical inactivity is a primary cause of most chronic diseases. The initial third of the article considers: activity and prevention definitions; historical evidence showing physical inactivity is detrimental to health and normal organ functional capacities; cause versus treatment; physical activity and inactivity mechanisms differ; gene-environment interaction (including aerobic training adaptations, personalized medicine, and co-twin physical activity); and specificity of adaptations to type of training. Next, physical activity/exercise is examined as primary prevention against 35 chronic conditions [accelerated biological aging/premature death, low cardiorespiratory fitness (VO2max), sarcopenia, metabolic syndrome, obesity, insulin resistance, prediabetes, type 2 diabetes, nonalcoholic fatty liver disease, coronary heart disease, peripheral artery disease, hypertension, stroke, congestive heart failure, endothelial dysfunction, arterial dyslipidemia, hemostasis, deep vein thrombosis, cognitive dysfunction, depression and anxiety, osteoporosis, osteoarthritis, balance, bone fracture/falls, rheumatoid arthritis, colon cancer, breast cancer, endometrial cancer, gestational diabetes, preeclampsia, polycystic ovary syndrome, erectile dysfunction, pain, diverticulitis, constipation, and gallbladder diseases]. The article ends with consideration of deterioration of risk factors in longerterm sedentary groups; clinical consequences of inactive childhood/adolescence; and public policy. In summary, the body rapidly maladapts to insufficient physical activity, and if continued, results in substantial decreases in both total and quality years of life. Taken together, conclusive evidence exists that physical inactivity is one important cause of most chronic diseases. In addition, physical activity primarily prevents, or delays, chronic diseases, implying that chronic disease need not be an inevitable outcome during life.
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Mental practice is the cognitive rehearsal of a task prior to performance. Although most researchers contend that mental practice is an effective means of enhancing performance, a clear consensus is precluded because (a) mental practice is often defined so loosely as to include almost any type of mental preparation and (b) empirical results are inconclusive. A meta-analysis of the literature on mental practice was conducted to determine the effect of mental practice on performance and to identify conditions under which mental practice is most effective. Results indicated that mental practice has a positive and significant effect on performance, and the effectiveness of mental practice was moderated by the type of task, the retention interval between practice and performance, and the length or duration of the mental practice intervention.
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The outgrowth of peripheral nerves and the development of muscle fiber-specific neuromuscular junctions were examined in Drosophila embryos using immunocytochemistry and computer-enhanced digital optical microscopy. We find that the pioneering of the peripheral nerves and the formation of the neuromuscular junctions occur through a precisely orchestrated sequence of stereotyped axonal trajectories, mediated by the selective growth cone choices of pioneer motoneurons. We have also examined the establishment of the embryonic muscle fibers and, using intracellular dye fills, have identified cells that are putative muscle pioneers. The muscle fibers of the bodywall have completed their morphogenesis prior to the initiation of synaptic contacts, and owing to the timing of neurite outgrowth from the CNS, synaptogenesis is synchronous at muscle fibers throughout the bodywall. At each muscle fiber the innervating axons make their initial contacts on a characteristic surface domain of the target cell's membrane. Through stereotyped growth cone-mediated trajectories the motoneurons actively establish the basic anatomical features of the mature neuromuscular junction, including the stereotyped, muscle fiber-specific branch anatomy. These events occur without significant process pruning or apparent synapse elimination. Our results suggest that the basic elements of the mature neuromuscular innervation, including the details of the ending trajectory on the target cell's surface, are formed by the precise navigation and presumed recognition by the motoneuron growth cones of muscle membrane surface features.
Early during neuromuscular development, acetylcholine receptors (AChRs) accumulate at the center of muscle fibers, precisely where motor growth cones navigate and synapses eventually form. Here, we show that Wnt11r binds to the zebrafish unplugged/MuSK ectodomain to organize this central muscle zone. In the absence of such a zone, prepatterned AChRs fail to aggregate and, as visualized by live-cell imaging, growth cones stray from their central path. Using inducible unplugged/MuSK transgenes, we show that organization of the central muscle zone is dispensable for the formation of neural synapses, but essential for AChR prepattern and motor growth cone guidance. Finally, we show that blocking noncanonical dishevelled signaling in muscle fibers disrupts AChR prepatterning and growth cone guidance. We propose that Wnt ligands activate unplugged/MuSK signaling in muscle fibers to restrict growth cone guidance and AChR prepatterns to the muscle center through a mechanism reminiscent of the planar cell polarity pathway.
The time course of strength gain with respect to the contributions of neural factors and hypertrophy was studied in seven young males and eight females during the course of an 8 week regimen of isotonic strength training. The results indicated that neural factors accounted for the larger proportion of the initial strength increment and thereafter both neural factors and hypertrophy took part in the further increase in strength, with hypertrophy becoming the dominant factor after the first 3 to 5 weeks. Our data regarding the untrained contralateral arm flexors provide further support for the concept of cross education. It was suggested that the nature of this cross education effect may entirely rest on the neural factors presumably acting at various levels of the nervous system which could result in increasing the maximal level of muscle activation.
The purpose of this study was to determine the extent to which scientific research influences college strength and conditioning coaching practices and to determine the training methods utilized. A total of 321 surveys were mailed to Division I strength and conditioning coaches, and the response rate was 42.7% (137 of 321 surveys). Results indicate that all subjects held a baccalaureate degree, the majority in a human performance-related field, and that 75% were Certified Strength and Conditioning Specialist (CSCS) certified. The respondents' most widely utilized professional resources were the Strength and Conditioning Journal (94%) and other collegiate coaches and programs (93%). Forty-seven percent of respondents indicated that other collegiate coaches and their programs were the most important sources of knowledge outside of formal education. The majority indicated that they used a periodization protocol (93%) utilizing multiple sets (97%), plyometrics (90%), explosive movements (88%), and Olympic lifts (85%). Respondents tend to rely on sources of information that may not be defined as scientific, as evidenced by the low priority given to peer-reviewed literature. Respondents also tend to employ the methods they utilized as athletes. Reliance on these sources may not take advantage of advances made through scientific research in exercise physiology, biomechanics, and more specifically the area of strength and conditioning.