Drivers Beware:
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8 Reasons to Avoid Sit-ups

by Dennis Zacharkow, PT
© 2014

The potential problems associated with sit-up exercises are as follows:

  1. Sit-up exercises primarily strengthen the upper rectus abdominis muscle (Teshima, 1958; Lipetz and Gutin, 1970; Girardin, 1973; Rasch and Burke, 1978). Based on subjective comments, the limiting factor in repetitive sit-ups is discomfort in the rectus abdominis muscle (Legg, 1981).

    According to Schultz (1983), "In a maximum voluntary attempted trunk flexion the rectus abdominis muscles provide about 40 percent and the medial groups of the internal and external oblique muscles each provide about 25 percent of the strength." These "upper abdominals" should be grouped with the flexors of the body, whereas the important postural "lower abdominal" muscles are grouped with the extensors of the body (Rathbone, 1934, 1936).

  2. Rectus muscle activity is not involved in maintaining or raising the intra-abdominal pressure (Floyd and Silver, 1950; Bartelink, 1957; Ono, 1958).


  3. Figure 1: The "postural depression" in kyphotic sitting postures is very similar to the "postural depression" resulting from sit-up exercises. From Bradford, E.H., and Stone, J.S.: The seating of school children. Transactions of the American Orthopaedic Association, 12: 170-183, 1899.
    Sit-up exercises reinforce the movement pattern of spinal flexion with minimal hip flexion (Zacharkow, 1984). This can contribute to ingraining poor technique when lifting, bending, or leaning forward in a chair.

    The "postural depression" resulting from sit-up exercises, by approximating the front of the chest to the pelvis, is very similar to the "postural depression" in kyphotic sitting postures (Anderson, 1951; Posse, 1890). (Figure 1.)

  4. Exercises that tend to increase the thoracic spine flexion are detrimental to good posture (Powell, 1930). Among adolescent females, Toppenberg and Bullock (1986) found the greater degrees of thoracic kyphosis to be associated with the shorter lengths of the rectus abdominis muscle. Kendall (1965) noted the tendency for overdeveloped upper abdominal muscles in the common postural fault of round upper back.

  5. Overemphasis on the rectus abdominis muscle can have an adverse effect on postural correction.

    "Often the upper abdomen is constricted by overdevelopment of the upper rectus abdominis. This is especially true in women who are conscious of a prominent abdomen and who are expending misdirected effort to overcome the condition. If continuous effort is made to flatten the abdomen and the result is a constriction or deep crease just below the level of the ribs, the lower abdominal wall is made weaker and less effective in supporting organs, and the effort expended to make the abdomen less prominent does not produce the desired results" (Drew, 1945).

    Frost (1938) found that with forced flattening of the abdomen, "most of the hollowing effect is in the upper abdomen, the sub-costal region, which involves definite interference with the free functioning of the diaphragm."

  6. As the spine is forced into maximum flexion, full sit-ups will cause a marked rise in lumbar intradiscal pressure, comparable to bending forward twenty degrees with ten kilograms in each hand (Nachemson and Elstrom, 1970). Halpern and Bleck (1979) commented that repeated sit-up activity "may as a side effect be causing or at least contributing to degenerative changes of the lumbar disk." White and Panjabi (1978) hypothesized that "the loads that are created on the discs by sit-ups can be expected to contribute to degeneration and failure of annular fibers."

    Mutoh et al. (1983) reported twenty-nine cases of low back pain at a Tokyo hospital over a one year period related to sit-up exercises with the knees extended and the ankles supported. Of the twenty-nine cases, the diagnosis included twenty-two cases of lumbosacral strain (75.9 percent) and four cases of a lumbar disc lesion (13.8 percent).

  7. Sit-up exercises promote trunk mobility, whereas training for trunk and pelvic stabilization are more important with abdominal exercises (Watanabe and Avakian, 1960; Armstrong, 1965, Zacharkow, 1984).

    Armstrong (1965) stressed that "a full range of movement of the spinal column itself is very rarely necessary to or even compatible with mechanical efficiency of the body as a whole. One of the main features of the development of a good active posture is the acquisition of the ability to brace the spine at or nearly at the neutral position so that it provides a stable centre from which the limbs can act with maximum efficiency."

  8. The last point in regards to potential problems with sit-up exercises is rarely mentioned, but of major importance. McKenzie (1915) stressed that at the beginning of a supine trunk flexion movement, the lower abdominal obliques remain relaxed, and the lower inguinal regions tend to bulge. This is important to realize when advocating full or partial sit-ups for individuals who already have a weak, relaxed lower abdominal wall.

    "In the movements of straight flexion of the trunk the rectus muscle only is employed at the beginning and the relaxed oblique muscles are distended, forming two distinct pouches or weakened areas over the lower abdomen, and by the time they contract in self-protection the mischief may have been done.

    It is in such conditions and under such circumstances that hernia is likely to be acquired, because hernia, like other swellings, enlarges in the line of least resistance. Perhaps one of the most potent causes is a standing posture in which the abdomen is protruded and the chest sunken, forcing down the abdominal contents on the relaxed lower zone, and I have been struck with the number of cases in which hernia came on unconsciously, without apparent cause, other than perhaps a long walk or a fatiguing day's standing. Even repeated and violent effort seems less fruitful of cases than the dull and steady pressure on the relaxed abdominal walls" (McKenzie, 1915).

    Bowen (1919) also stressed that with a weak abdominal wall, abdominal exercises should be avoided that do not bring the oblique muscles into action. "Direct flexion of the trunk by raising the head and shoulders from lying position is risky because it begins with isolated action of the rectus" (Bowen, 1919).

References

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