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Mathew F. Bunch 08-19-2006 05:52 AM

this is in reference to the 15 august wod caption: i wonder if back extensions and regular sit-ups are a good indicator of strength/endurance discrepency. one starts horizontal and ends vertical, getting easier through the range of motion while the other starts vertical and ends horizontal. even that oversimplifies the difference as part of the trunk is supported during the first half of the sit-up (with the exception of ghd situps) so there is less of a load on the stomach muscles than during the back extension where the load is constant.

i would think a better comparison would be vertical situps (hanging from a bar or strapped into an inversion board) versus the back extension or regular situps versus good mornings without weight.

moreover, i have noticed the opposite discrepency when doing ghd sit-ups versus ghd back extensions-i can do about 20 proper situps versus about 55-60 back extensions.

Steven Low 08-19-2006 08:34 AM

Interesting observation. I think you're right. The posterior chain is usually stronger with more endurance overall in general. The only thing that seems to be able to get anterior dominated are the shoulders/chest/rotator cuffs and quads, and that's only with excessive exercise towards the imbalances.

Ross Hunt 08-19-2006 11:49 AM

IMO, the discrepancy reported on the front page is surprising, and probably does have a lot to do with the 'rest' during the sit-up.

I wonder how the ratios would look (for CrossFitters or for other athletes) when strength rather than strength endurance is compared in the two exercises. I've done weighted glute-ham sit-ups, and let me tell you, they're HARDER than back extensions. The range of motion is just so much huger. The back extension actually seems quite comparable to the glute-ham sit-up in difficulty if I only lower my torso to parallel to the ground on the sit-up, pausing there for a moment-- it's getting from hip angle at ~225 degrees to hip angle at 180 degrees that's the killer.

I haven't done the glute-hams for a while, though. Those mess with my back, even with proper extension of the leg.

John Seiler 08-20-2006 02:46 AM

"One comment on the discrepancy...we ran this challenge by first having everyone to a static hold. Once the challenge was completed we had everyone do a max sit up and max back ext effort. So with Cill only getting 57 back extension we must say that she may well of have had more if she had not had just completed a 2:20 sec hold. There is no doubt that most of us are deficient in our back ext....and will start to rememdy..thanks coach"

Comment #102 - Posted by hollis at August 15, 2006 10:16 AM

I found this comment to be most intriguing. It doesn't matter too much to me as I'm weak in both areas so will gladly work on any defiency. Still, I be interested to hear some follow-up on it.

Roger Harrell 08-21-2006 07:55 AM

In a weighted back extension you can get more of a whip than in a weighted glute ham situp (dependant on how you're doing the weighting and how flexible your shoulders are). This makes the back extension a bit easier when weighted, so it may be more of a mechanics thing.

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