Transcript Slide 1

EMG Activity of the Trunk Stabilizers During Stable and
Unstable Environments
Elliott, B, Gaetz, M. and Anderson, G.
Discussion:
Training the core muscles of the trunk has application in personal
training, rehabilitation and injury prevention. Training to enhance
the functioning of the core muscles has been a “hot topic” of late,
with the introduction of many pieces of apparatus to enhance the
core muscle activation during exercise.
The purpose of this study was to quantify the core muscle
activation during exercises performed on various commercially
available apparati that introduce an unstable training surface —
the BOSU and Stability balls. The hypothesis was that there would
be greater core muscle activation during exercises performed on
unstable surfaces.
Table 1: Significance of results
Side bridge
Significant
Significant
Internal obliques
Methods:
Curl-up
Not significant
Not significant
N/A
Fifteen highly trained conditioning coaches performed 5 exercises
(bridge, bridge (one leg), side bridge, curl up and the superman)
on a stable surface (the floor), and two unstable surfaces (BOSU
dome and Stability ball). Surface electrode electromyography was
recorded over the Rectus Abdominus, Erector Spinae, and Internal
Oblique muscle groups. A root mean square of the EMG was
calculated for each muscle and each exercise condition. Data
were analysed using a Univariant General Linear Model ANOVA,
with Boneferroni post-hoc comparisons. Significance was set at
the P≤0.05 level.
Superman
Not significant
Significant
Erector spinae
Condition
Stable/Unstable
Muscle
Significance
Not significant Significant
Bridge
Bridge-1 foot Not significant Significant
Most active
Muscle
Erector spinae
Erector spinae
Exercise 1 – Bridge
120
Mean Muscle Activation
The use of highly trained conditioning coaches may explain these results.
These individuals routinely “set the core” by activating the core muscles
during most exercises. Setting the core increases muscle activation during
exercises performed on a stable surface, reducing the difference we might
expect to see in a general population. It is hypothesized that significant
differences in muscle activation would be seen across exercises performed
on stable and unstable surfaces when using an untrained population, or
those that are not accustomed to instability training.
The exercise with the greatest core muscle activation was the curl up to
45° of trunk flexion in both the stable or unstable environments. This was,
however, the only dynamic exercise and this result should be expected.
Internal Obliques EMG Means
During Various Exercis es
100
Exercise 2 - Bridge, 1 Foot
80
Stable
60
Exercise 3 - Side Bridge
40
unstable
Exercise 4 - Curl up
20
0
The present hypothesis could not be supported for any of the exercises
except the side bridge. No significant differences were found between
stable and unstable conditions using the bridge, single leg bridge, curl up
or superman exercises. However, while not significant there was a trend
with muscle activation being higher for most muscles during exercise
performed on unstable surfaces.
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Exercise
The side bridge was the only exercise to show a significant stability effect.
This corresponds to that exercise which the subjects found most
challenging in the unstable environment and probably accounts for the
significant increase in muscle activation.
Exercise 5 - Superman
5
Conclusion:
Results:
Mean Muscle Activation
300
Mean Muscle Activation
ANOVA results indicated a significant main effects for stability and
muscle. Significance during stable and unstable exercise was
found during the side bridge exercise only. Muscle activity within
exercises was significantly different for all exercises but the curl
up. The erector spinae showed greatest activation during both the
two foot and one foot supported bridge, whereas the internal
obliques were the most active during the side bridge. During the
superman the erector spinae was the dominant muscle during
stable conditions while the internal obliques were dominant during
the unstable exercise. When comparing the 5 exercises, the curl
up was the exercise that maximally activated the muscles of the
trunk.
Erector Spinae EMG Means
During Various Exercis es
250
200
150
100
50
0
Increased EMG activation of core trunk stabilizers using unstable surfaces
was observed for the side bridge only. An non-significant increase in core
Rectus Abdominus EMG Meansstabilizer EMG observed during exercises performed on an unstable
During Various Exercis es
surface. While studies have demonstrated a significant affect using a
100
stability ball in the past, the present study was unable to duplicate this
80
finding in highly trained conditioning coaches. Significance was only found
60
in that exercise that was found to be most challenging. For this reason it is
40
hypothesized that instability training may be beneficial in those with little
20
previous exposure to training on unstable surfaces.
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Exercise
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Exercises
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Acknowledgement:
This study was supported by the University of the Fraser Valley
JUSTICE INSTITUTE OF BRITISH COLUMBIA