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Oct 01,2005

Home : Fitness : Oblique Facts About Abs Workouts

Oblique Facts About Abs Workouts

by JohnH

By John Higgins

We all know lots of different abdominal exercises. Some of these exercises, we believe, are better for training the side abs (the obliques), some for the lower and others for the upper abs. But what does science have to say about this? Until recently not a lot, which is why a team of researchers from the University of Nebraska designed a study to measure the amount of muscle activity in the side, lower and upper areas of the abdomen musculature during commonly-used abs exercises.

Measuring muscle activity involves recording an EMG (electromyographic) signal, which shows the amount of electrical activity on the surface of an active muscle. A lot of EMG signal means the muscle is very active, whereas little or no signal means it is inactive. By comparing a muscle's EMG signal during an exercise with the signal during a maximal contraction, you can work out the relative level of muscle activity during the exercise and compare different muscles during the same exercise or the same muscle during different exercises. For example, if the quadriceps produce an EMG signal which is 20% of max during a bodyweight squat and 45% of max during a bodyweight lunge, we can conclude that the lunge is a more demanding exercise.

In this experiment, the researchers took EMG readings from three sites - the upper portion of the rectus abdominis (above the naval), the lower portion of the same muscle (below the naval) and the external oblique. They did this for five different exercises, as follows:

Abs curl. This exercise is performed lying on the back with knees bent at 900 and hips flexed to about 450. Keeping the lower back on the floor, the subject curls up neck and shoulders until shoulder blades clear the floor;

Reverse curl. Same start position, but instead of curling shoulders up the subject curls up legs and buttocks off floor;

Twisted curl. Same start position, but with left ankle resting on right knee and left knee pointing away. Subject curls up right shoulder towards left knee;

V-sit. Same start position but subject curls both shoulders and lower body up together;

Abs hollowing. This involves standing up and sucking in naval and abdomen as much as possible.

The researchers had assumed - and most trainers would agree - that the Ab curl would produce the biggest upper rectus EMG signal, the twisted curl the biggest oblique signal and the reverse curl the biggest lower rectus EMG signal. However the results were a little surprising, with key findings as follows:

There was no real difference in upper rectus activity for exercises 1-4. Therefore, it appears that for dynamic abs exercise, this muscle works equally hard, regardless of the different types of movement.

The reverse curl and the V-sit exercise produced the biggest lower rectus and oblique EMG signals. As expected, the lower portion of the rectus muscle works harder when the exercise involves curling the lower body but, surprisingly, so do the oblique muscles. This suggests that the obliques play an important role in lumbar flexion movement, which is more demanding than trunk rotation.

The abs hollowing exercise produced little upper or lower rectus activity but significant oblique activity. The fact that rectus is not involved in this movement is predictable, as the hollowing movement comes (or should come) from the deep tranversus muscles which run under and across the rectus. The hollowing movement is associated with good lumbar stabilisation, and again the obliques are important in producing this movement.

The practical implication of these findings is that it is worthwhile varying your abdominal exercises to ensure that all the areas of the abdomen musculature are worked. However, the upper portion works equally hard regardless of exercise and, contrary to what you might assume, lower limb and lumbar flexion movements work the obliques better than twisting movements.

The best all-round exercise from this selection is the V-sit, as it produces the highest average EMG signal in all three muscle areas.

John has experience in many areas of health and fitness and shares this Fitness Information on his website www.Fitness4Living.co.uk