# What muscle is used in sit-ups (not the abs)?

**URL:** <https://boards.straightdope.com/t/what-muscle-is-used-in-sit-ups-not-the-abs/848675>\
**Category:** Factual Questions\
**Created:** [February 28, 2020, 7:54pm UTC](https://boards.straightdope.com/t/what-muscle-is-used-in-sit-ups-not-the-abs/848675 "2020-02-28T19:54:58Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![jebert](https://avatars.discourse-cdn.com/v4/letter/j/ec9cab/32.png) [@jebert](https://boards.straightdope.com/u/jebert)\
**Post date:** [February 28, 2020, 7:54pm UTC](https://boards.straightdope.com/t/what-muscle-is-used-in-sit-ups-not-the-abs/848675/1 "2020-02-28T19:54:58Z")

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From what I’ve heard, the old-fashioned sit-up, the kind where someone holds your feet down and you raise your whole truck, doesn’t exercise the abs so much as some muscle or muscles in the upper leg. What muscles are these? I need to know because I injured one about 3 years ago, and it still hurts.

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**Author:** ![DinoR](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dinor/32/2821_2.png) [@DinoR](https://boards.straightdope.com/u/DinoR)\
**Post date:** [February 28, 2020, 8:06pm UTC](https://boards.straightdope.com/t/what-muscle-is-used-in-sit-ups-not-the-abs/848675/2 "2020-02-28T20:06:30Z")

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I think you are looking for the group of muscles grouped together as the [hip flexors](https://www.verywellhealth.com/the-hip-flexors-definition-3120388#hip-flexor-muscles).

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**Author:** ![Shodan](https://avatars.discourse-cdn.com/v4/letter/s/9f8e36/32.png) [@Shodan](https://boards.straightdope.com/u/Shodan)\
**Post date:** [February 28, 2020, 8:08pm UTC](https://boards.straightdope.com/t/what-muscle-is-used-in-sit-ups-not-the-abs/848675/3 "2020-02-28T20:08:16Z")

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The iliacus and psoas major. [Cite](https://en.wikipedia.org/wiki/Psoas_major_muscle).

Once your shoulder blades are off the floor, the abs function mostly isometrically.

Regards,  
Shodan

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**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\
**Post date:** [February 28, 2020, 8:08pm UTC](https://boards.straightdope.com/t/what-muscle-is-used-in-sit-ups-not-the-abs/848675/4 "2020-02-28T20:08:38Z")

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The iliacus and the psoas.