Resistance Training for the Abdominals

11 Dec

No other muscle group has elicited as much discussion as the muscles that comprise the abdominal region. The abdominal muscles consist of the rectus abdominis (main function of trunk flexion), internal and external oblique (main function trunk rotation and lateral flexion) and the transverse abdominis (main function of abdominal compression). In fact all four muscles act as an abdominal compressor and trunk stabiliser, although the internal oblique and transverse abdominis are more directly involved in stabilisation through their attachment to the lumbar spine. The rectus and obliques act in unison to produce flexion.

Abdominal exercise selection (indeed any exercise selection) depends upon the goals to be addressed. One or more of the following may be required from your abdominal program; cosmetic (looking better), strength/power (for sport), function (posture and injury prevention) or rehabilitation. It is imperative that you match the exercises performed to your goals in what is termed the SAID principle (Specific Adaptation to Imposed Demands). For example if you goal is to improve posture, then slow or static movements will give the best results as the muscle activation patterns of the exercise match the required result. Conversely if sporting prowess is needed then dynamic or explosive movements would result in more closely matched muscle activation patterns. Remember that abdominal exercises are not exclusively performed while lying supine on the floor. Exercises can be done whilst standing to complement the movement patterns of the sport.

For best results the principle of progressive overload must also be adhered to. That means that over time the intensity of the exercise must be increased. This can be achieved a number of ways. Most common is to increase the number of repetitions performed per set or to increase the volume by performing more total sets or reducing rest periods between sets. This will result in minimal strength but good endurance gains. Less common is to increase the load on the abdominal region by adding weight to the exercise or to increase the difficultly of the exercise itself through manipulation of body levers or body position. This will result in minimal endurance but good strength gains.

Two recent studies used EMG (electromyographic) technology to determine the best abdominal exercise (abdominal meaning rectus abdominis). In a San Diego University study the traditional crunch movement was tested and given a score of 100 as the reference and the other movements were scaled accordingly. The results are as follows:

Bicycle Manoeuvre – 248
Hanging Knee Raise – 212
Exercise Ball Crunch – 139
Vertical Leg Crunch – 129
Ab Wheel – 127
Long Arm Crunch – 119
Reverse Crunch – 109
Crunch with Heel Push – 107
Ab Roller – 105
Crunch – 100
Bridge – 100
Straight Arm Pulldown – 92
Ab Rocker – 21

Note that although the fact that thirteen exercises were tested, a large number were not. Only the rectus activation was examined, not the obliques.

At the University of Nebraska five movements were studied. A trunk curl (crunch), reverse trunk curl, v-sit and trunk curl with twist had similar rectus activation. The v-sit and reverse curl resulted in greater amounts of oblique activity, while the vacuum had some oblique and little rectus activation.
Listed below are some research Facts and implications

  • The body is a dynamic system of interactive muscle groups and the trunk should be trained in flexion,extension and rotation
  • Resisted back exercise is vital for producing trunk stability. The erector group often need more attention than the abdominals
  • Psoas (not iliopsoas) involvement increases when the feet are restrained. Often back pain from sit-ups is a result in sciatic nerve overstretching
  • Dynamic contraction of the abdominals occurs between –15 degrees and +30 degrees from the horizontal. Beyond +30 degrees involves isometric abdominal contraction and concentric hip flexor contraction
  • Sit-ups tend to be safer and effective when performed slowly without initial jerking or bouncing, concentrating on strongly contracting the abdominals through both the concentric and eccentric phases
  • Lumbar safety is enhanced if the lower spine is kept in mild flexion during a full sit-up or in contact with the floor during a partial sit-up, via the use of posterior pelvic tilt Abdominal resistance work needs to be balanced by full range abdominal and hip flexors stretches

Cissik, J.M. (2002) Programming abdominal training, part 1. Nat Strength & Cond Ass 24(1):9-15.
Cissik, J.M. (2002) Programming abdominal training, part 2. Nat Strength & Cond Ass 24(2):9-12.
San Diego State University(2001) as reported in Mens Health. December, 30.
Willet, G.M. et al (2001). Relative activity of abdominal muscles during commonly prescribed strengthening exercises. J of Strength & Cond Research 15(4):480-485.
Young, W. (1998) Specificity of abdominal muscle function. Strength & Cond Coach 6(2):2-9.
Siff, M.C. (2000) Facts and Fallacies of Fitness. Mel C Siff PhD, Denver.