64 Dance Anatomy and Kinesiology
Electromyography
Examples of EMG records of three muscle groups for danc-
ers directed to stand in first position, “prepared,” as if they
were in class, is shown. Records from two professional ballet
dancers and two advanced modern dancers were selected to
show the range in response with the same position. With this
version of testing, the magnitude of the tracing of a muscle
during a given movement is compared to that of a maximum
voluntary contraction of the same muscle with the same
electrode application.
Key:
A = hip adductor (adductor longus)
Q = quadriceps femoris (vastus medialis)
H = hamstrings (biceps femoris)
FIRST POSITION–BALLET
TESTS AND MEASUREMENTS 2.1
movement set into play by gravity. For students new to
anatomy, this is a difficult concept to grasp. It is help-
ful to consider whether the movement of the body or
its segments is primarily (1) opposite to the direction
of gravity (upward) or (2) in the same direction as
gravitational forces (downward). For slow, controlled
movements, movements opposite to the direction of
gravity are generally produced by concentric muscle
contraction of muscles whose action is the same as
the direction of movement, while movements in the
same direction as gravity will be produced by gravity
and controlled by eccentric contraction of muscles
whose action is in the opposite direction to the joint
movement occurring.
For example, in a plié in first position (figure
2.21), the up-phase would be going against gravity,
and the knee extensors (quadriceps femoris) would
be working concentrically to produce knee exten-
TABLE 2.5 Simplified Movement Analysis of Demi-Plié in Parallel First Position
Phase
Hip joint
motion
Hip muscle
group
Type of
contraction
(sample
muscles)
Knee joint
motion
Knee
muscle
group
Type of
contraction
(sample
muscles)
Up-phase Hip
extension
Hip
extensors
Concentric
(gluteus
maximus,
hamstrings)
Knee
extension
Knee
extensors
Concentric
(quadriceps
femoris)
Down-phase Hip flexion Hip
extensors
Eccentric
(gluteus
maximus,
hamstrings)
Knee flexion Knee
extensors
Eccentric
(quadriceps
femoris)
Selected key joints: Hip, knee
S7
A
Q
H
S13
A
Q
H
FIRST POSITION–MODERN
S9
S3