Why ab workouts shouldn't include this exercise...
Over the years, numerous routines and techniques have been promoted
as a way to make your ab workouts more effective.
Some exercises work better than others. However, a Swedish research
team has found one exercise included in many ab workouts that has
virtually no effect on the abdominals.
Before you continue, it's important to keep in mind that there
are many different abdominal muscles.
In this study, the term "abdominals" refers to rectus
abdominis, along with the external and internal obliques.
Learn
more about the abdominal muscles (pop-up window).
As part of their study, researchers from Stockholm's Karolinska
Institute compared the double leg raise with the single leg raise
using electromyography (known simply as EMG). EMG can be
used to measure muscle recruitment during various exercises.
Surface electrodes were placed on the skin over the rectus abdominis,
obliquus externus, obliquus internus, rectus femoris, and sartorius
muscles and with indwelling fine-wire electrodes from the iliacus
muscle.
The double leg raise, which involves raising both legs from the
floor at the same time, was found to activate both the abdominal
muscles and the hip flexors.
The single leg raise involves raising just one leg from
the floor. Although it activates the hip flexors, the results show
that the single leg raise requires virtually no work from
the abdominals at all!
The question is, why?
During the double leg raise, the abdominals work to keep your pelvis
"stable".
However, the fact that the other leg rests on the floor during
the single leg raise appears to be enough to stabilize the pelvis
while the other leg is lifted.
The result is that the single leg raise requires very little work
from the abdominal muscles. Unless you've been told otherwise
by a therapist, it's probably best to leave this exercise out
of your ab workouts.
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References
1. Andersson, E.A., Nilsson, J., Ma, Zhijia, M., & Thorstensson,
A. (1997). Abdominal and hip flexor muscle activation during various
training exercises.
European Journal of Applied Physiology and Occupational Physiology,
75, 115-123
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