The Muscular System 67When one is designing a stretching exercise for
a given muscle, the approach is different. Here a
position is utilized that is opposite to, versus the
same as, at least one of the primary actions of the
muscle such that the given muscle is put in a posi-
tion of elongation. As previously described, three
repetitions of a 30-second slowly applied stretch of
low to moderate intensity appear to be an effective
approach for improving flexibility. This method of
stretching, where a position is maintained, is termed
static stretching. Another effective approach, termed
PNF contract-relax (proprioceptive neuromuscular
facilitation), utilizes a 5- to 10-second contraction of
the target muscle immediately followed by a 10- to
20-second stretch, with this sequence repeated three
times (Shrier and Gossal, 2000; Tanigawa, 1972;
Wallin et al., 1985). While this is frequently used
for stretching outside of class, fewer repetitions and
shorter-duration stretches are commonly employed
within the dance class for a majority of muscle groups
due to other programming considerations such as
class flow, maintenance of the elevated temperature
of the body, and time constraints because of the many
other essential class objectives.
With two-joint muscles, the desired position of
stretch is often achieved by incorporating elonga-
tion of the muscle across both joints, at least to some
degree. For example, when stretching the hamstring
muscle, a more flexible dancer would likely use a
position of hip flexion and knee extension to pro-
duce an effective intensity of stretch on the ham-
strings such as seen in figure 2.23A. However, this
combined use might create too great an intensity of
a stretch or not allow appropriate positioning of the
body for a less flexible individual. In such a case, the
knee can be slightly bent to allow correct position-
ing and an appropriate intensity of stretch either in
a sitting position or in a supine position as shown in
figure 2.23B. Gravity can be utilized in many ways
during stretching of muscles. However, positions will
often be used in which gravity tends to approximate
either the proximal or the distal body segment such
that stretch intensity is increased. In the sitting ham-
string stretch shown in figure 2.23A, gravity will tend
to bring the trunk (proximal segment) closer to the
thigh to increase hip flexion and stretch intensity. In
the supine hamstring stretch shown in figure 2.23B,
gravity will tend to bring the thigh (distal segment)FIGURE 2.23 Influence of body position on hamstring stretching. (A) Sitting, (B) supine, and (C) standing.