In
this literature review, the question, “What is the effect of core training on
athletic performance?” will be explored to see if core training really does
improve an athlete’s performance. This is a widely discussed area in sport and
is well studied. Personal trainers talk about “training the core”, but what
they are usually referring to is just the abdominal muscles which is incorrect.
The “core” is the area below the pectoral muscles, down to and including the
hips. This is the area from which the body stabilises itself, so its
extremities - such as arms, head and legs - can move efficiently. A strong core
means stronger arms and legs which will improve any movement whether it is
running, jumping, throwing etc. The literature's reviewed range from 1992 and
2014.
The
core can be scientifically defined as “the trunk or more specifically the lumbo-pelvic
region of the body” (Willardson 2007). Most people misinterpret the meanings of
core stability and core strength. Core stability means “The ability to
control the position and motion of the trunk over the pelvis to allow optimum
production, transfer and control of force and motion to the terminal segment in
integrated athletic activities” (Kibler. 2006,
Lawrence 2007, Willson JD, Davis 2005). A stable core prevents the body moving into
incorrect planes of motion such as having an anterior pelvic tilt and will
prevent any injuries in the trunk area.
Core strength can be defined as “the muscles
surrounding the spinal column’s ability to maintain stability while acting on
an external perturbation” (Hibbs 2008, Akuthota,
Nadler 2004). When completing either
strength training, endurance training or stability training, we are making the
core more efficient at these roles.
Core
training has two key roles: -
“1/
the first role is protecting (stabilizing) the spine from excessive (and
potentially injurious) forces.
2/ the
second is in the creation and transfer of forces in a proximal to distal
sequence” (Brumitt, 2010, Panjabi,1992)
In
theory the effect of core training on athletic performance for either a power
based sport or an endurance based sport, should improve performance. The reasons
we need to have a strong core is because the core is the base for all movements
our body makes. When we throw, push, pull or jump, the core is always involved
to give the body a stable base to work off. A stronger core increases the
strength/power/endurance capabilities of the upper and lower extremities. Mark
Rippetoe further confirms that the core is used for transferring power/force to
the extremities (Rippetoe, 2009).
In
this literature review we will be looking at the effect of core training in NFL
(National Football League) players (power/strength sport) and comparing their
results with 5000m runners results (endurance sport).
“The Relationship between Core Stability and
Performance in Division 1 Football Players” Nesser, TW, Huxel, KC, Tincher, JL,
and Okado, T. (2008)
“Does Core Strength Training Influence Running
Kinetics, Lower Extremity Stability and 5000m Performance in Runners”. Kimitake. S, Monique. M (2009)
These
are diverse sports, each of which requires different skills and different
components of fitness. NFL requires more strength and power which relies
heavily on the ATP-PC energy system, whereas the 5000m runners rely upon
muscular endurance and aerobic capacity to complete their task. However, the
common denominating factor is that both of these sports need a strong and
efficient set of core muscles to carry out their prescribed sporting demands.
 |
| Credit: https://keithclinic.com/posts/exercise-tips/core-strength-beyond-the-six-pack/ |
Reviewing
these studies, both sets of subjects improved their performance - one group
minimally and one group significantly. The 5000m metre study showed that during
the testing, the CST (Core Strength Training) group had a significant
improvement in 5000m times after 6 weeks of implementing their core training
intervention. It should be mentioned CST did not significantly influence GRF
(Ground Reaction Force) variables and lower-leg stability. The CST group
average time improved by 47 seconds and the control group improved by 7 seconds
on average. There were minimal differences in pre and post climates for the
5000m tests performed. The main difference between the pre and post was the
introduction of the core strengthening programme and increase in training
volume/intensity. It could be theorised that the introduction of this core
training may have influenced the results (Kimitake, Monique 2009).
The NFL study showed that with core training,
their athletes’ performances only improved marginally. The results of this
study indicated that core stability is moderately related to the strength and
performance of the athlete. They concluded that “increases in core strength are
not going to contribute significantly to strength and power improvements and
should not be the focus of the strength and conditioning” (Nesser, Huxel,
Tincher, Okado, 2008). The aim of this
study was to “determine whether core strength is related to more specific
measurements of strength and power in strength and power athletes”. The 29 male
athletes were tested during their pre-season. The independent variables which were
used to measure the athletes’ core strength/stability included back extension,
trunk flexion, right and left side bridge. The dependent variables are the 1RM
(one repetition maximum), CMJ (Countermovement Vertical Jump), Pro Agility
Shuttle Run, 20 yard and 40 yard Sprints.
Reviewing
both studies highlighted certain limitations. In
the 5000m study the data for both the GRF groups were affected by inconsistent
running velocity due to the subjects not following experimental protocol which
resulted in inaccurate pre and post-test times. Subjects ran faster post-test
but were instructed to run at same speed (at a natural pace) pre-test for a
more reliable and valid comparison between pre and post training GRF tests. However,
especially within the CST group, its subjects ran faster during the post
training GRF test (Kimitake, Monique 2009). This improvement, specifically in
the CST group, may be due to the subjects putting more effort in and possibly
manipulating results - this is described as the Hawthorn Effect. This is known as
“Participant’s performance changes when attention is paid to them, which is
likely to reduce the ability to generalize the results” (Thomas, Nelson,
Silverman, 2011). This enhancement will have affected the internal validity of
the study due to the subjects not following the specific instructions. The
Hawthorn Effect may have been present in this study as they were testing
themselves to try and improve their own scores. Their study does mention the enhancement
in the results which includes the factor of “test/re-test”.
It
could be summarised that the internal validity is affected more as the subjects
were given a second attempt to improve their 5000m times. This led to a
noticeable difference in temperature, pre =86 F (Fahrenheit), 64% humidity; post=73 F, 58% humidity (Kimitake,
Monique 2009). Running in a hot environment
makes the body work harder as it has to sweat more to keep the body cool and
this excessive sweating costs the body lots of sodium and energy. Endurance
training in hot environments will decrease in performance over time (Armstrong
1986, Neilsen
2003, Nybo 2004, Lepage 2011). Another
factor which may have affected the results is the body shape and mass of the
runners. The control group were slightly heavier than the experimental group so
their times would have been slower on average when compared. However internal
validity is verified as the subjects were randomly allocated in this study.
 |
| Credit: https://www.studyblue.com/notes/note/n/trunk-muscles/deck/16843955 |
When analysing the results of the NFL study,
they are not consistent. It can be seen that there is too much variance around
the mean as shown from Table 2 below.
Having a large variance around the mean of
results reduces the validity and reliability of the study.
(Nesser,
Huxel, Tincher, Okado, 2008).
The
study incorporated McGill’s core stability tests which are taken from his own
study which was solely to find and “collect isometric endurance times from a
healthy normal population performing the "side bridge" or lateral
flexion exercise, as well as isometric flexion and isometric extension
exercises”. These endurance times can be used to form "normal"
relative ratios to guide clinicians and identify endurance deficits within
specific patients” (McGill, 1999).
 |
| Dr Stuart McGill. Image Credit: https://kabukistrength.com/category/articles/dr-stuart-mcgill/ |
However, there is a major limitation using
McGill’s testing methods as McGill was testing for a different component of
fitness i.e. Muscular Endurance and in Nesser’s study he is applying these
tests to power and strength athletes. Using a test aimed at endurance then
comparing it to tests of 1RM, CMJ, Agility Testing and 20/40 yard will not
produce a significant difference in pre and post test results. With using an
inappropriate method of testing and the study’s own results being inconsistent
we can conclude that the “The Relationship between Core Stability Training and
Performance in Division 1 Football Players” isn’t reliable to determine if core
training has an impact on power/strength athlete’s performance.
However,
this doesn’t mean that core training won’t have any benefit for strength/power
based athletes. As shown from the Kata Karate study, their performance improved
(Sameh, Tantawi 2011). Looking at Justin Shinkle’s study the Effect of
Core Strength on the Measure of Power in the Extremities – it states that “Core
strength does have a significant effect on an athlete’s ability to create and
transfer forces to the extremities” (Shinkle 2012). Strength and power athletes
such as powerlifters and weightlifters, may not need to do specific core
exercises as they are always using their core muscles for their sport (squats,
cleans, snatches). In theory, their core stability is constantly improving as
they are constantly engaging their core.
Another
point of note from the 5000m study, is that the CST group became more aware of
their posture when running, which in turn may have contributed to a better
post-test result. When asked for their feedback the subjects were more
conscious of their core muscles to stabilize themselves when running (Kimitake,
Monique 2009). The study did state that their own work may have produced this
improvement due to more training sessions compared to others which only did 2
sessions per week over a 6 week period. A higher training volume is needed to
increase core strength which may have improved 5000m running times post-test
(Kimitake, Monique 2009). This again brings in the Test Re-Test Effect and
Hawthorn Effect.
It has
been proven that better posture when running does improve biomechanics which in
turn improves performance through more efficient running mechanics as shown
from numerous studies such as “The Effects of Posture on Running Performance: A
Case Study” (Comereski, Niedzielski 2004). These results showed that by doing postural
repositioning exercises over a 5 week period, the performance of the track
athlete improved. Postural repositioning focused on getting the pelvis into a
neutral position, stretching the lower back muscles, strengthening the weaker
core muscles such as obliques - this led to an improvement in performance.
Improvement was shown from a 14 second improvement over 1 mile and 6 second
improvement over the 800m.The main limitations for this study are that it was
only performed on one individual.
To summarise all the literature reviewed, it could
be postulated that core training is important for all athletes but it has more significance
for those athletes who partake in endurance events. This is supported from the 5000m
study by Kimitake,
Monique 2009. It could be theorised that
endurance sports utilize the core muscles to a greater extent and for a longer
period. This is evidenced as core training has significantly more of an impact
on endurance athletes than power/strength athletes. It could be argued that whilst
competing in endurance events, these core muscles are being used for longer and
have a greater stress placed upon them - especially the diaphragm muscles when
breathing. The abdominals need to be very strong and energy efficient to help improve
an athlete’s ventilation ability (increase rate and depth of breaths).
Looking at the demands of the core muscles on an
NFL athlete, they need to be able to contract and relax quickly to produce a
large amount of force/power and be able to stabilize itself when releasing this
force upon or towards an object. This happens for a few seconds and then stops.
This “stop start” (interval) way of this sport, doesn’t require their athletes
to place a huge significance onto core training. Perhaps NFL could focus more
on compound movements to improve their performance such as squats, deadlifts,
cleans etc which works the whole body and engages the core muscles in a way
that has a positive effect towards their sport.
In conclusion, analysis and comparison shows that
the results from the 5000m study shows very positive data (such as 47 second improvement). However, the NFL study is
significantly different, as their athletes minimally improved. This could be
due to different testing procedures, internal/external variables influencing
the data and different subjects for each group having their own individual
effects on the data collection.
When
compared to the power/strength studies of NFL their performances did improve
but not to the same extent as the 5000m runners. The NFL subjects improved
marginally on their strength/power tests after their core intervention. The NFL
evidence is flawed due to the testing methods, as the study used endurance
tests exercise programme.
In future research regarding the topic of core
training, practitioners should devise a core test protocol which is generic and
then create sport specific core tests relevant to strength and conditioning
core training programmes for their athletes. Core training is still a developmental
part of sports science today as we are still learning how it can be most
effective and applicable to different sports.
------------------------------------------------------------------------------------------------------------------------
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Andrew Richardson, Founder of Strength is Never a Weakness Blog
I have a BSc (Hons) in Applied Sport Science and a Merit in my MSc in Sport and Exercise Science and I passed my PGCE at Teesside University.
Now I will be commencing my PhD into "Investigating Sedentary Lifestyles of the Tees Valley" this October 2019.
I am employed by Teesside University Sport and WellBeing Department as a PT/Fitness Instructor.
My long term goal is to become a Sport Science and/or Sport and Exercise Lecturer. I am also keen to contribute to academia via continued research in a quest for new knowledge.
My most recent publications:
My passion is for Sport Science which has led to additional interests incorporating Sports Psychology, Body Dysmorphia, AAS, Doping and Strength and Conditioning.
Within these respective fields, I have a passion for Strength Training, Fitness Testing, Periodisation and Tapering.
I write for numerous websites across the UK and Ireland including my own blog Strength is Never a Weakness.
I had my own business for providing training plans for teams and athletes.
I was one of the Irish National Coaches for Powerlifting, and have attained two 3rd places at the first World University Championships,
in Belarus in July 2016.Feel free to email me or call me as I am always looking for the next challenge.
Contact details below;
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