In an athletic strength and conditioning setting there is never enough time. This is why it’s always important to select exercises that give the most return for the time spent on them. This applies to core training as well as everything else. While I’m a firm believer that squats, pulling movements, the Olympic lifts, overhead presses, and hip hinges will strengthen the core adequately, I also understand some wanting to do more.
Axler and McGill published a study more than 20 years go that inv4stigate a dozen core exercises and looked at how well they recruited abdominal muscles. The results are interesting.
The authors investigated straight leg sit ups, bent leg sit ups, curl up feet fixed, curl up feet free, quarter sit up, bent leg raise, cross knee curl up, static cross knee curl up, hanging straight leg raise, hanging bent leg raise, and the side plank.
Results:
- In terms of external oblique activation; the hanging straight leg raise was first with bent leg sit ups, cross knee sit ups, dynamic and static cross knee curl ups, straight leg sit ups, and the hanging bent knee raises all a close second. The bent leg raise was lowest.
- In terms of upper rectus abdominis activation, straight leg sit ups, hanging straight leg raises, and bent leg sit ups were first through third. The bent leg raise was lowest.
- The authors also looked at lumbar spine compression and found that the sit ups and cross knee movements had the greatest compressions.
The hanging straight leg raise ended up being one of the most effective exercises in the study. It was first at recruiting the external obliques and a close second at recruiting the upper rectus abdominis. It was also in the middle in terms of lumbar spine compression. Surprisingly sit ups were also extremely effective at recruiting both muscle groups, though they were higher in terms of compression.
When selecting exercises it’s important to understand the risks and to carefully weigh the returns from the exercise against the time required for it that could be spent on other things.
Axler, C.T. and McGill, S.M. (1997). Low back loads over a variety of abdominal exercises: Searching for the safest abdominal challenge. Medicine and Science in Sports & Exercise, 29, 804-811.
