Abdominal Exercises

Abdominal muscles help support the lower back. Therefore, strong abdominal muscles can decrease the risk of developing lower back pain. When doing abdominal exercises on the deck, only a portion of the abdominal's range of motion is being strengthened because your lower back is flattened. However, by placing a rolled towel under your lower back you can extend the range of motion for abdominal exercises (see Figure 8-1).

Figure 8-1. Range of Motion of the Abdominals

Flexion (75-90°)

Extension (30°)

X

Neutral (0°)

A rolled towel under the

lower back increases trunk

extension when performing

abdominal exercises.

Towel

In this section two common abdominal exercises, the curl-up and the crunch, will be described. The curl-up, used on the PRT as a measure of muscle endurance, targets both the abdominal and hip flexor muscles. The form for the curl-up is:

From OPNAVIST 6110.1E

♦ Lie on back with knees bent, feet flat on
deck, heels 10 inches from buttocks and held
down by a partner. Cross arms and hands on
chest or shoulders.

♦ Curl torso up, touching elbows to upper
thighs while hands remain on the chest or
shoulders. Exhale as you lift.

♦ Lie back until the lower edge of your
shoulder blades touches the deck. Inhale as
you lower.

The crunch is similar to the curl-up but is performed within a smaller range of motion. The torso is lifted by abdominal muscles during a crunch. The form for the crunch is:

♦ Lie on back with knees bent 90°, feet flat on
deck, shoulder width apart. Do not anchor
your feet. (Anchoring your feet or placing
your legs out straight on the deck will target
your hip flexors, not your abdominals.)

♦ Place fingertips lightly on the back of the
head, elbows out to sides and in line with

ears. (Variations to this include arms at sides, arms across chest, and arms above head.)

♦ Lift torso until the shoulder blades come off the deck by moving
rib cage toward hips. Exhale as you lift. Look up at the ceiling to
prevent neck strain.

♦ Return to the starting position. Inhale as you lower.

Some people may develop lower back pain if they perform curl-ups routinely. For them, the crunch is recommended as an alternate exercise. Regardless of which exercise you choose when training, focus on the quality, not the quantity, of repetitions. If you perform either exercise rapidly, you are using momentum and not building abdominal strength!