|
PRACTICAL
SIGNIFICANCE
Compared
to
basketball
players,
dancers
showed
non-significant
trends
towards
higher
hamstrings
and
lower
quadriceps
muscle
activity
during
drop
landings.
Continued
research
examining
other
possible
ACL
protective
movement
strategies
employed
by
dancers
is
necessary.
STUDY
BACKGROUND
Anterior
cruciate
ligament
(ACL)
injuries
of the
knee do
occur
during a
drop
landing
movement
pattern.
Although
both
dancers
and
athletes
regularly
perform
landings
during
their
activities,
dancers
reportedly
have
lower
rates of
ACL
injury
than
athletes.
During
activity,
greater
knee
muscle
co-activation
can
increase
knee
joint
stiffness
and can
be
protective
by
minimizing
extreme
joint
range of
motion.
Dancers
have
been
reported
to
demonstrate
diminished
H-reflexes
(indicating
higher
muscle
co-activation
levels)
than
active
controls.
Whether
dancers,
who
undergo
years of
disciplined
jump
training,
use
different
neuromuscular
strategies
than
traditional
athletes
that may
modify
knee
joint
stiffness
and
allow
for ACL
injury
protection
during
activity
remains
unknown.
OBJECTIVE
The
focus of
this
work was
to
compare
knee
muscle
activation,
knee
joint
stiffness
(KJS),
and
ground
reaction
forces (GRFs)
between
female
dancers
(D) and
basketball
players
(B)
during
double-leg
drop
jumps
(DJ).
DESIGN
AND
SETTING
This
study
utilized
a
descriptive
cohort
design
and took
place in
the
Applied
Neuromechanics
Laboratory
on the
campus
at UNC
Greensboro.
SUBJECTS
Thirty-five
dancers
(age
20.7±2.3yrs,
height
164.3±6.7cm,
mass
62.2±1.9kg),
and 20
female
basketball
players
(age
20.1±2.0yrs,
height
170.5±6.1cm,
mass
72.6±11.4kg)
participated
in this
investigation.
MEASUREMENTS
All
participants
performed
five DJs
from an
established
height
of 45
cm.
Surface
electromyography
was used
to
measure
the
muscle
onset
times
(ms) and
mean
amplitudes
(%MVIC)
before (pre=150
ms)
and
after (post=50
ms)
ground
contact
in the
following
muscles:
lateral
gastrocnemius
(LG),
medial
and
lateral
hamstring
(MH, LH)
and
lateral
quadriceps
(LQ).
A 3D
electromagnetic
sensor
tracking
system
and
forceplatform
was used
to
measure
peak
GRFs
(BW) and
sagittal
KJS
(knee
moment
change/
flexion
angle
change
from
ground
contact
to
maximum
knee
flexion;
Nm/kg°)
during
landing.
RESULTS
In this
study,
no group
differences
existed
between
onset
times
(D=133.4±53.2ms,
B =
121.6±50.2ms;
P=.22)
and
amplitudes
(pre:
D=28.1±8.7%MVIC,
B=27.7±10.5%MVIC;
P=.60;
post:
D=51+17.3%MVIC,
B = 49.6
±
21.4%MVIC;
P=.78)
for all
muscles
and for
KJS
(D=.016±.01Nm/kg°,
B = .018
±.01
Nm/kg°;
P=.44).
Dancers
exhibited
higher
GRFs
than
basketball
athletes
(D =
4.26 ±
.9BW; B
= 3.68 ±
.6BW;
P=.01).
Moderate
effect
sizes
for the
dancers
indicated
trends
towards
higher
activation
levels
in the
medial
hamstrings
pre
and
post
landing,
and in
the
lateral
gastrocnemius
muscle
post
landing.
However,
the
dancers
also
demonstrated
lower
lateral
quadriceps
activity
observed
after
ground
contact.
CONCLUSIONS
Although
muscle
activation
amplitudes
and
onsets
did not
differ
statistically,
the
moderate
effect
sizes
observed
does
suggest
a
meaningful
difference
may
exist
between
these
groups.
While
KJS did
not
differ
between
the
groups,
higher
GRFs
noted in
the
dancers
may
potentially
indicate
neuromechanical
differences
exist
across
other
joints.
Further
research
is
needed
to
conclusively
determine
if
dancers
possess
different
neuromuscular
characteristics
during a
landing
activity
compared
to
traditional
athletes.
|
Publication
and
Presentation
List:
-
Ground
Reaction
Forces,
but
not
Knee
Muscle
Activation,
or
Sagittal
Knee
Joint
Stiffness
Differ
between
Female
Dancers
and
Basketball
Players
during
Drop
Jumps,
MAATA
Annual
Meeting,
Free
Communications
Presentation,
Virginia
Beach,
VA,
May
2007.
-
Ground
Reaction
Forces,
but
not
Knee
Muscle
Activation,
or
Sagittal
Knee
Joint
Stiffness
Differ
between
Female
Dancers
and
Basketball
Players
during
Drop
Jumps,
NATA
Annual
Meeting,
Free
Communications
Presentation,
Anaheim,
CA,
June
2007.
|
|
Jatin P. Ambegaonkar, PhD, ATC, OT, CSCS
Principal Investigator |
|
Jatin P. Ambegaonkar recently completed his Doctorate in Exercise and Sport Science from the University of North Carolina at Greensboro in May 2007. Prior to completing his PhD, he earned his M.S. degree in Sport Injury Prevention & Management from Spring College, and his B.S. degree in Occupational Therapy from the University of Mumbai in India. Currently, Dr. Ambegaonkar is an Assistant Professor and Coordinator of Clinical Education at George Mason University. Additionally, he also serves as the Co-Director of the Sports Medicine Assessment, Research and Testing Laboratory. |
| |
Jatin P. Ambegaonkar, MS, ATC, CSCS, OT
George Mason University
4283, Mazarin Place Apt 402
Fairfax, VA 22033-5796
703 993 2123
Fax: 703 993 2025
jambegao@gmu.edu |
|
|
This
Grant
Information
Summary
may be
downloaded
in a
2-page
pdf file
from
http://www.natafoundation.org/pdfs/07Ambegaonkar.pdf. |
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