||SuperAbs Resource Manual
Len Kravitz, Ph.D.
Although you are regularly bombarded with exercises claiming to tone and strengthen the abdominal muscles, many of these exercises are inadequate and ineffective. Some exercises may actually lead to lower back pain, and do little to strengthen the abdominals. The purpose of this manual is to provide accurate, useful information and exercise guidelines for abdominal training. In addition, several myths and misconceptions about abdominal training will be dispelled.
ANATOMICAL AND KINESIOLOGICAL REVIEW
Before proceeding, a brief anatomical and kinesiological overview of the abdominal muscles is necessary. The mid-section muscles consist of the rectus abdominis and the internal and external obliques. The rectus abdominis is a long, flat band of muscle fibers extending vertically between the pubis and the cartilages of the fifth, sixth, and seventh ribs on the front part of your trunk. Its right and left halves are separated in the middle by a strong tendinou sheath known as the linea alba (which means white line). There are three horizontal tendinous creases that give the muscle that washboard appearance on some individuals. The muscle is enclosed in a sheath formed by the aponeurosis (broad, flat, and thin connective tissues) of the other abdominal muscles. The rectus abdominis flexes the spinal column, bringing the rib cage and/or the pelvis toward each other, and assists in sideward bending. The rectus abdominis is also actively involved in stabilizing the trunk when the head is raised in a supine (lying on back) position (Luttgens & Wells, 1992).
The external oblique muscles are the outermost fibers of the trunk, and are located on each side of the rectus abdominis. Their upper and lateral attachments are to the lower eight ribs by tendinous insertions that interdigitate (interlock like the fingers of folded hands) with the serratus anterior muscle on the side of the rib cage. The lower and middle attachments of the external obliques are to the anterior crest of the pelvis (iliac crest) and the aponeurosis of the linea alba from the ribs to the crest of the pubis. The external oblique muscle actually becomes the inguinal ligament #(Hay & Reid, 1982)#. The fibers of this muscle run diagonally, forming a V shape, similar to putting your hands into your coat pocket.
Beneath the external oblique muscles, running at approximately right angles to them, are the internal oblique muscles which form an inverted V shape. Their upper and medial attachments are to the cartilages of the lower three ribs and the aponeurosis of the linea alba. Their lower and lateral attachments are to the inguinal ligament, the crest of the pelvis, and the fascia (connective tissue) of the lower back (erector spinae). At the lower end the internal oblique muscle fibers run almost horizontally. Both the external and internal oblique muscles are involved in flexing the rib cage and the pelvic bones together, sideward bending (lateral flexing) of the trunk, and rotating the trunk. The external obliques are referred to as opposite side rotators. Due to the muscle fiber arrangement, when you rotate to the left, the external oblique fibers on your right side facilitate the movement. Conversely, if you rotate to your right, the left external oblique fibers help with the movement. On the other hand, the internal oblique muscles are same side rotators. Thus, if you rotate to the left, the left internal oblique muscles facilitate the movement. When you rotate to the right, the right internal oblique muscles help cause the motion.
Due to the fact that the lower fibers of the internal oblique muscles run horizontally, they also are strong trunk rotators (Luttgens & Wells, 1992)#. Although most people think of the oblique muscles as being only frontal muscles, it is important to note that their fan-like fibers extend all the way around the sides to the lower back in much the same way a corset fits a person.
The deepest layer of abdominal muscles, the transversus abdominis, is not involved in movements of the trunk (Rasch & Burke, 1978). Instead, this respiratory muscle plays an important function in forceful expiration of air from the lungs; as well as compression of the internal organs.
The villains of abdominal training are the hip flexors, which bring the legs and trunk toward each other. Muscles that flex the hip include the psoas major, illiacus, rectus femoris, pectineus and sartorius. Full sit-ups involve the hip flexors, which may cause the lower back to arch and unwanted back pain, particularly in individuals with relatively weak abdominals (Mutoh, Mori, Nakamura, & Miyashita, 1981). Leg-raising exercises in a supine position challenge the hip flexors with limited involvement of the abdominals (Libetz & Gutin, 1970). Frequently, there is a muscle imbalance between the weaker abdominals and the stronger hip flexors in trunk flexing movements (Kendall & McCreary, 1993). The goal of abdominal training is to maximize the involvement of the abdominals, while minimizing the involvement of the hip flexors (Walters & Partridge, 1957).
DISPELLING SOME WIDELY BELIEVED MYTHS
Can you effectively work the abdominals in a standing position?
Standing static contractions (contracting without movement) of the abdominal muscles are helpful (and recommended) in developing good spinal posture, especially in learning how to tilt your pelvis backward (posterior pelvic tilt). Many individuals stand with their hips tilted forward (anterior pelvic tilt) due to tight or excessively shortened hip flexors. This position may exaggerate the arch in the lower back (Plowman, 1992); however, strong abdominals can counteract this anterior pelvic tilt by pulling up on the pelvis (Glisan & Hochsculer, 1990). Also, gravity and the weight of your torso make standing abdominal work significantly less effective than supine abdominal exercises.
What about the standing side-to-side exercise?
Many people think that side-to-side (lateral flexion) bending is a good exercise to shape the sides of the torso. This is not true because deeper spinal muscles can perform this exercise much more efficiently than the abdominal muscles. In fact, the quadratus lumborum muscle, which attaches from the crest of ilium to the transverse processes of the lumbar vertebrae and to the lowest rib, is actually a pure lateral flexor muscle. Anatomically, the quadratus lumborum is positioned so that it is more active than the external obliques during side bending (Rasch & Burke, 1978). The soreness that many people associate with a firming of the oblique muscles is actually a result of overstretching these muscles and doing the movements too fast. It should be noted that slow, controlled, alternating lateral flexion of the trunk is an effective exercise for increasing lateral range of motion for the spine.
Are standing rotation exercises just as ineffective?
Yes, those movements are performed without resistance and oftentimes with great speed. This may create undesirable rotational stress and wear and tear on the spinal vertebrae. However, many health clubs now have new equipment which offer resistance to trunk rotation and flexion in the upright and supine positions. Individuals choosing to use this equipment should have a qualified trainer check their exercise technique because its easy to perform some of these exercises incorrectly.
Can you work the upper and lower abdominals independently? When performing some abdominal exercises, it often feels like the muscle is divided into an upper and lower section. Although the abdominal muscles have intersegmental nerve stimulation, you are not able to contract one section independent of the other. However, when you stabilize the hips and only lift the trunk, there is relatively more muscle shortening in the upper abdominal region which leads to greater muscle involvement in that region (Walters & Partridge, 1957). In addition, the internal obliques are more involved in this torso lifting action (Kendall, McCreay, & Provance, 1993). Conversely, when you perform reverse crunches (lifting the pelvis off the floor), there is more shortening in the lower region, challenging the lower abs relatively more than the upper abs as well as more involvement of the external obliques (Kendall, McCreay, & Provance, 1993).
If you do many abdominal exercises, will you lose additional body fat in the abdominal region?
In a landmark study by researchers at the University of Massachusetts, it was conclusively shown that sit-up exercise training does not decrease the diameter of abdominal adipose cells, abdominal subcutaneous fat (skinfold thickness) or abdominal circumference (Katch et al., 1984). Therefore, you cannot use ab exercises to selectively lose abdominal fat. Instead, to reduce fat content at a given body site, your total body fat will have to be altered.
Are the abdominal muscles active during normal walking?
It may be surprising, but electromyographic (EMG) analysis of the abdominal muscles has demonstrated that the abdominal muscles are quite inactive during walking on a flat surface (Sheffield & Major, 1962). EMG analysis is the scientific method of measuring the muscles electrical activity and contractility during movement, very similar to the way an electrocardiogram (ECG) measures heart rhythm. The rectus abdominis and external oblique muscles exhibit little electrical activity in an erect posture unless the trunk is inclined backward or laterally and/or resistance is applied to the torso (Walters & Partridge, 1957). The internal obliques, on the other hand, are in a state of tension while sitting, standing and walking, to help stabilize the pelvis (Floyd & Silver, 1950; Walters & Partridge, 1957).
Do you work the abdominals when performing those hanging leg lifts from a chin-up bar?
Although the hip flexors are the prime movers in bringing the legs up toward the chest in this movement, the abdominals are statically (no movement) contracting in this exercise. Several studies demonstrate conclusively the involvement of the abdominal muscles in this skill (Flint & Gudgell, 1965; Guimaraes, Auerlio, Campos, & Marantes, 1991; Gutin & Lipetz, 1971). In the hanging leg lift, the rectus abdominis must rotate the pelvis posteriorly and stabilize the pelvis to allow the legs to move freely toward the chest. Since the legs are relatively heavy, the strain on the rectus abdominis is due largely to its role in stabilizing the pelvis. This exercise is quite strenuous for many individuals. Doing this exercise with straight legs places a heavy load on the lumbar spine, making this a high risk exercise for some individuals. Performing the hanging leg lifts with bent knees reduces this risk.
TRAINING FOR RESULTS
Now that weve dispelled several popular myths and clarified some important issues about abdominal exercises, lets verify some of the most effective means of training these muscles. Perhaps one of the most common and important questions asked about abdominal training is How high up should you go in a crunch (or curl-up)? Research suggests that the abdominals flex the spinal column for about the first 30 to 45 degrees of movement which is approximately equivalent to lifting your shoulder blades off the ground (Laban, Raptou, & Johnson, 1965; Plowman, 1992; Rasch & Burke, 1978; Ricci, Marchetti, & Figura, 1981). Beyond 30 degrees, the powerful hip flexors begin to take charge of the movement. Due to the potential pressure placed on the lower spine by the hip flexors, full sit-ups cannot be recommended. Plowman #(1992)# adds that bent knee, feet supported sit-ups may cause lumbar stress which could lead to harmful effects on the lumbar discs. Several studies indicate that supine crunches, with bent knees and unsupported legs, maximize abdominal activity and minimize hip flexor (specifically the rectus femoris) activity (Godgrey, Kindig, & Windell, 1977; Guimaraes et al., 1991; Libetz & Gutin, 1970; Walters & Partridge, 1957). Since the effectiveness of the abdominal exercises is within this small range of motion (30 - 45 degrees), more repetitions and exercises may have to be performed to appropriately challenge these muscles.
In the following sections, we will look at specific questions about training variables that can enhance the effectiveness of your abdominal workout.
Can I work the abdominal muscles daily?
Make sure you train them at least 3 - 5 days per week, with a daily workout being permissible. Unlike other muscles, you rarely fatigue the abdominal muscles enough so that they need an additional day to recover. This is because you are always working with the weight of your torso, in a limited range of motion, as compared to other exercises which may challenge the muscles with progressively heavier resistance. In practice, it actually makes sense to do some type of abdominal strengthening exercise on a daily basis to try and counteract the excessive tightening of your lower back muscles and hip flexors. Just because you may work the abdominals regularly, there should be no fear that these muscles will get too big. In fact, the abdominals are very thin muscles compared to other muscles, such as the deltoids, gluteals, hamstrings, biceps, and quadriceps. So, unless you are progressively overloading these muscles with additional external resistance, such as ab machines, it is unlikely that the abs will become too thick.
Then is it O.K. to use some resistance in working the abdominals?
Yes, but first make sure you are doing your abdominal exercises with correct technique. For effective abdominal training, emphasize body position and movement proficiency. Greater results will be attained with a focus on technique. Furthermore, do the exercises slowly, with control. How many times have you taught, gone to a class, or worked out at home using some high energy music, and then tried to adapt the abdominal workout tempo to the beat of the music? Focus more on the abdominal movement, trying to accentuate each contraction. In other words, make every repetition count. Try adding light handheld weights (2 to 4 lb) to several of the exercises only when you feel you really need that additional challenge.
Should I pull in the abdominals when doing crunches?
The rectus abdominis is actually slightly rounded in its relaxed state. Pulling the abdominals in while in a supine position with bent knees, may be an effective means of helping to bring your rib cage and pelvis towards one another, maximizing the effect of the crunch. It may help to visualize your abdominals compressing like an accordion. Pulling the abdominals in also helps some people flatten their lower back against the floor. There are some individuals who find it useful to exhale during the lifting phase, as this facilitates the contraction of the abdominals. Indeed, there is increased muscle EMG activity in the abdominal muscles with more pronounced exhalations (Partridge & Walters, 1959).
Is there an ideal sequence for working the abdominal muscles?
Some persons would like to convince you that there is an ideal sequence for working the abdominals, i.e., theirs, if you just buy their product. In actuality, research has demonstrated that your body is constantly learning how to adapt and respond to stimuli. If you were to present the same stimulus, i.e., the abdominal sequence, you would readily adapt to this routine so that it would eventually become ineffective in terms of shaping your midsection. The key word to remember for all resistance training is variety. You can add interest, creativity and challenge to your abdominal training program by varying the amount and type of each of the following:
repetitions and sets
number of exercises
position of exercise
tempo of exercise
type of contraction
Which type of contraction is best for abdominal training?
One way to add variety to your ab workout is to vary the type of muscle contraction used (shortening, lengthening, and static). Doing a crunch, when you lift the torso off the floor, the abs are shortening; whereas, in the trunk-lowering phase the abs are lengthening. During hanging leg lifts, the abs are contracting statically and there is no visible trunk movement. Sheffield & Major (1962) noted greater EMG activity and muscle involvement in the shortening contractions compared to lengthening contractions of the abs doing sit-ups.
What is the relationship between low-back health and abdominal training?
The back extensor muscles (predominantly the erector spinae and multifidus muscles) function mainly to provide posterior stability for the vertebral column and to oppose the force of gravity for maintaining erect posture and controlling forward flexion (Glisan & Hochsculer, 1990). Improper vertebral alignment can result from weak erector spinae muscles, leading to incorrect loading on the spine. If the back extensor muscles and associated connective tissues become weak and overstretched, possibly from spending a lot of time in a flexed, seated position, the lumbosacral angle decreases and the discs bulge posteriorly, resulting in low back pain (Calliet, 1988).
The key abdominal muscles for low-back health may be the internal obliques, as opposed to the rectus abdominis (Plowman, 1992). The abdominal oblique muscles attach to the connective tissue of the erector spinae muscles of the lower back. Strong internal oblique muscles reinforce the erector spinae fascia and pull it laterally. This reinforced fascia is therefore more efficient in supporting the spine. Thus the importance of working the oblique muscles for improved low-back health is justified. Partial sit-up or crunch exercises, with the knees flexed and ankles unsupported, are the best for strengthening the abdominal muscles, without risk to the lower back (Mutoh et al., 1981).
Since the external and internal obliques contract like a corset tightening, shouldnt we be doing more exercises for these muscles?
Great point. Most instructors do predominantly spinal flexion movements for the core of their abdominal workout. A balanced approach of spinal flexion, rotation, and lateral flexion in the backlying position is recommended. You should emphasize the involvement of all the abdominal muscle groups for abdominal shaping and low-back health reasons.
EXERCISE AND PERFORMANCE TRAINING TIPS
In designing an abdominal workout, choose between 5 to 10 exercises, combining spinal flexion, rotation, and lateral flexion exercises. Perform 8 repetitions of each exercise before going on to the next exercise. Every 2-3 weeks, you are advised to vary your workout (refer above for ways in which to vary your program). Strive for quality of movement with each contraction. Also, visualize your abdominal muscles contracting tighter with each exercise, stressing the importance of the contraction. Although its great to do these exercises with accompanying music, try not to let the music dictate the tempo of the exercise. Slow and controlled movement is always best. During all exercises for which you need to support your head, do so in a comfortable manner that does not allow you to force your chin towards your chest.
Although the abdominals are a troublesome spot for many people, the knowledge and tools you now have, will, with hope, highlight your abdominal exercise workout, while helping you achieve your health and fitness goals.
Cailliet, R. (1988). Low back pain syndrome (4th ed.). Philadelphia: F.A. Davis Company.
Flint, M., & Gudgell, J. (1965). Electromyographic study of abdominal muscular activity during exercise. Research Quarterly, 36, 29-37.
Floyd, W. F., & Silver, P. H. (1950). Electromyographic study of patterns of activity of the anterior abdominal wall muscles in man. Journal of Anatomy, 84, 132-145.
Glisan, B., & Hochsculer, S. H. (1990). General fitness in the treatment and prevention of athletic low back injuries. In S. H. Hochshuler (Ed.), The spine in sports (pp. 31-41). St. Louis, MO: Mosby-Yearbook, Inc.
Godgrey, K. E., Kindig, L. E., & Windell, J. E. (1977). Electromyographic study of duration of muscle activity in sit-up variations. Archives of Physical Medicine and Rehabilitation, 58, 132-135.
Guimaraes, A. C., Auerlio, M., Campos, M. I. A. E., & Marantes, R. (1991). The contribution of the rectus abdominis and rectus femoris in twelve selected abdominal exercises. The Journal of Sports Medicine and Physical Fitness, 31, 222-230.
Gutin, B., & Lipetz, S. (1971). An electromyographic investigation of the rectus abdominis in abdominal exercises. Research Quarterly, 42, 256-263.
Hay, J. G., & Reid, J. G. (1982). The anatomical and mechanical bases of human motion. Englewood Cliffs: Prentice-Hall, Inc.
Katch, F. I., Clarkson, P. M., Kroll, W., & McBride, T. (1984). Effects of sit-up exercise training on adipose cell size and adiposity. Research Quarterly for Exercise and Sport, 55, 242-247.
Kendall, F. P., McCreary, E. K., Provance, P.G. (1993). Muscles and testing function (3rd ed.). Baltimore: Williams & Wilkins.
Laban, M. M., Raptou, A. D., & Johnson, E. W. (1965). Electromyographic study of function of iliopsoas muscle. Archives of Physical Medicine and Rehabilitation, 46, 676-679.
Libetz, S., & Gutin, B. (1970). An electromyographic study of four abdominal exercises. Medicine and Science in Sports and Exercise, 2, 35-38.
Luttgens, & Wells, K,F. (1992). Kinesiology (8th ed). Dubuqe. W.C. Brown.
Mutoh, Y., Mori, T., Nakamura, Y., & Miyashita, M. (1981). The relation between sit-up exercises and the occurrence of low back pain. In H. Matsui &. K. Kobayashi. (Eds.), International series on biomechanics, Biomechanics VIII A (pp. 180-185). Baltimore: University Park Press.
Partridge, M., & Walters, C. (1959). Participation of the abdominal muscles in various movements of the trunk in man. Physical Therapy Review, 39, 791-800.
Plowman, S. A. (1992). Physical activity, physical fitness, and low back pain. In J. O. Holloszy (Ed.), Exercise and Sport Sciences Reviews (pp. 221-242). Baltimore: Williams & Wilkins.
Rasch, P. J., & Burke, R. K. (1978). Kinesiology and applied anatomy (6th ed.). Philadelphia: Lea & Fibiger.
Ricci, B., Marchetti, M., & Figura, F. (1981). Biomechanics of sit-up exercises. Medicine and Science in Sports and Exercise, 13, 54-59.
Sheffield, F. J., & Major, M. C. (1962). Electromyographic study of the abdominal muscles in walking and other movements. American Journal of Physical Medicine, 41, 142-147.
Walters, C. E., & Partridge, B.S. (1957). Electromyographic study of the differential abdominal muscles during exercise. American Journal of Physical Medicine, 36, 259-268.