124 Dance Anatomy and Kinesiology
important for correcting lumbar lordosis and creat-
ing a neutral pelvis during functional movement and
may involve more activation of muscle fibers located
lower in some of the abdominal muscle groups.Adequate Range of Motion Full sit-ups with the
legs straight have been shown to only recruit various
abdominal muscles from 20% to 34% of the time
(Halpern and Bleck, 1979) and are associated with
greater use of the hip flexors (Ricci, Marchetti, and
Figura, 1981) and greater stresses to the spine (Axler
and McGill, 1997) than curl-ups. Hence, the trend
for abdominal work has been to substitute smaller
range curl-ups where various abdominal muscles are
active 90% to 93% of the time, and there is probably
less lumbar stress. However, this trend can be taken
too far, such that inadequate range is utilized to
provide necessary abdominal overload. In the very
beginning phase of the curl-up, the neck flexors
and rectus abdominis are primarily working. As
the torso curls higher (up to about 40 to 50°) the
obliques are recruited and the abdominals work
harder (length–tension principle), achieving about
50% of a maximum voluntary contraction with 45°
of flexion (Floyd and Silver, 1950; Sheffield, 1962;
Soderberg, 1986). After about 50° of spinal flexion,
the hip flexors become more primary and activation
of the abdominals decreases. Hence, an effort should
be made to keep the back of the sacrum in contact
with the floor and fully flex the spine (30 to 45°)
rather than the common error of either only flex-
ing the spine slightly and barely raising the torso off
the ground in the exercise or only flexing the spine
slightly and then primarily using the hip flexors to
raise the torso further. Using a larger range of spinal
flexion is also important for dancers because some
dance movements (such as getting up and down
from the floor in modern and jazz) incorporate a
full range of motion, and strength gains are specific
to the range worked, declining markedly the farther
away the angle is from that used for strengthening.Type of Muscle Contraction One way of working
a fuller range of motion in dancers who do not have
adequate strength to curl up very high (concentric
contraction), as seen in figure 3.41A, is to use isomet-
ric or eccentric contractions. For example, after one
curls up concentrically, the hands can be used to pull
the shoulders up slightly higher (e.g., to flex the spine
further). The hands are then released, and either
the position is held (isometric contraction) as seen
in figure 3.41B and table 3.4B (p. 134) or the torso
is slowly lowered back down to the floor (eccentric
contraction). Since greater force can be generated
with an eccentric or isometric contraction than with aconcentric contraction, strength can be developed at a
range higher than could be reached with a concentric
contraction alone. One can apply this same principle
by starting from a sitting position and curling back
toward the floor (eccentric contraction) as seen in
figure 3.41C and table 3.4C (p. 134). Lower ranges
can be held isometrically (to add more overload) and
then, initially, the hands can be used to pull on the
legs to assist with coming back up to sitting (concentric
contraction). As strength increases, use of the hands
can be lessened and then discontinued.
Spinal Rotation Adding rotation to relevant
abdominal exercises such as a curl-up will cause
greater challenge to the oblique abdominal muscles.
When one is performing a straight curl-up, both
sides of the external oblique and internal oblique
muscles can act with the rectus abdominis. However,
when rotation is added, some of the obliques are
antagonists to the movement, and only the internal
oblique on the same side (ipsilateral) as the direc-
tion of movement and the external oblique on the
opposite side (contralateral) of the direction of the
movement can aid with the movement.
Use of Adequate Overload To produce desired
improvements in muscular strength, the abdominal
exercises should be difficult enough that one can
perform about 12 repetitions at the most. If more
repetitions can be performed, the difficulty should be
increased, for example by working in a higher range
(up to about 40° or 50°), adding trunk rotation, bring-
ing the feet closer toward the buttocks when they are
on the floor (Hall, Lee, and Wood, 1990), bringing the
legs up (90° hip and knee flexion) with the lower legs
in the air or supported by the seat of a chair or bench
(Gutin and Lipetz, 1971), bringing the arms farther
away from the navel to increase the moment arm of
the resistance (e.g., from by the sides to across the
chest, supporting the head, or reaching overhead), or
adding external resistance such as dumbbells held in
the hands. Furthermore, remember that the effect of
gravity on the body is primarily creating the resistance
in these exercises. Therefore the body must be appro-
priately positioned so that the abdominal muscles are
having to work against gravity, such as when one is
performing a curl-up from a supine position or a side-
up from a side-lying position. In contrast, exercises
that neglect this principle related to gravity, such as
standing full-waist circles or standing reaches, are so
ineffective in terms of overload that they are virtually
useless for abdominal strengthening.
Recovery After 6 to 12 repetitions of an appropriate
exercise, one should allow recovery of the abdomi-
nal muscles for 2 to 3 minutes before performing