492 Dance Anatomy and Kinesiology
These joints and selected movements are particularly
key in running. The action of the arms appears to
function primarily to counterbalance the off-center
thrust of the legs (Adrian and Cooper, 1989). However,
a more complete analysis would include the smaller
movements of abduction-adduction and external rota-
tion-internal rotation of the hip and knee, as well as
movements of the pelvis (tilts and rotations), spine,
upper extremity, and key joints of the foot. Although
these movements may be smaller or less fundamental
for moving the body through space, they are essential
for running mechanics, and deviations in these move-
ments are often implicated with common technique
errors and overuse injuries.
In terms of stabilizers, one key muscle group is
the hip abductors. During the stance phase, these
muscles play a key role in preventing excessive
undesired lateral tilt of the pelvis (Trendelenburg
sign) or lateral excursion of the pelvis relative to the
support foot. In terms of flexibility, although a visual
evaluation of running does not display requirements
for extreme ranges of motion commonly seen in
dance movements, many runners exhibit suboptimal
levels of flexibility at various joints, and inadequate
range of ankle dorsiflexion can result in compensa-
tory excessive pronation during the support phase.
Similarly, tight hip flexors can produce an undesired
excessive anterior tilt of the pelvis and limit the
desired positioning of the pelvis as the leg swings
forward such that stride length is negatively affected.
Although still controversial, adequate hamstring
flexibility may also have a positive effect on running
performance and reduced injury risk (Hreljac, Mar-
shall, and Hume, 2000; Koceja, Burke, and Kamen,
1991). In terms of strength, research has shown that
adequate “knee lift” (requiring hip flexor strength)
and high levels of hip extensor strength are key for
high-level sprinting performance. The latter element
of strength is key for increasing the power of the leg
drive for greater acceleration of the runner.
In terms of technique, one common error is
to swing the gesture leg around (circumduction)
during the recovery phase. Cueing the runner to
“swing the knee forward on a slight diagonal line”
(slightly toward the midline) versus “swinging the
knee around in a small semicircle” can help achieve
desired positioning. Unnecessary lateral motions
decrease the efficiency of running and decrease
forward propulsion (Hamilton and Luttgens, 2002).
Similarly, cueing to drive the back leg downward and
backward at push-off with correct timing and posi-
tioning of the trunk can help achieve optimal for-
ward propulsion. The desire is to produce a ground
reaction force with a large horizontal componentthat will propel the runner forward without excessive
vertical movement of the body. Positioning of the
foot when it contacts the ground at the beginning of
stance phase is also key for determining the ground
reaction forces generated. Since the ground reaction
force is equal in magnitude but opposite in direction
to the force produced by the foot when it contacts the
ground, having the lower leg still moving forward or
having the foot land well in front of the line of grav-
ity (extending vertically from the center of mass of
the whole body) will produce a forward force on the
floor resulting in a ground reaction force that pushes
the body backward, termed a braking force. Avoid-
ing swinging the leg too far forward (“overstriding”)
and cueing runners to think of “pulling the ground
toward them” when the foot strikes can help reduce
braking forces and enhance running economy.
In terms of special considerations, the goal of
running in athletics (such as long-distance running
vs. sprinting) will also influence optimal mechan-
ics, supplemental conditioning, and appropriate
cues. For example, research has demonstrated that
a successful endurance runner is characterized by
less vertical oscillation, slightly longer strides, less
change in velocity during the ground contact, and
a lower first peak in the vertical component of the
ground reaction force, associated with a tendency to
have smaller braking forces (Kyrolainen, Belli, and
Komi, 2001). These characteristics are associated
with greater running economy or efficiency, and the
lower peak vertical forces (impact forces) that are less
rapid in development may also reduce injury risk in
runners (Ferber et al., 2002; Hreljac, 2004; Hreljac,
Marshall, and Hume, 2000).
In dance, the goal often has more to do with
meeting the aesthetics of the choreography versus
optimizing economy or speed. For example, a cho-
reographer may desire that running be performed
low to the ground, maintaining the knees in flexion
and emphasizing horizontal movement of the body.
In another case, the choreographer may desire more
of a “prance,” emphasizing vertical movement of the
body at the expense of horizontal movement. So,
although many of the principles just discussed with
running are still relevant, the movement will often be
shaped by aesthetic versus biomechanical criteria.Leap (Grand Jeté en Avant)
In kinesiology, a leap is defined as a locomotor
movement that involves taking off from one leg and
landing on the opposite leg, while a jump involves
takeoff and landing on both feet. The leap analyzed
in table 8.7 follows these criteria. However, in many