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With summer rolling around, many of us are scrambling to find our abs. When it comes to ab training, the two exercises most people are familiar with are sit-ups and crunches. While these movement patterns may look similar, one is much more efficient for training the rectus abdominis (the 6-pack muscle).

The primary function of this muscle is spinal flexion, or decreasing the angle of the spine. If training the rectus abdominis is the goal, this is critical to keep in mind, as any other motion would be wasted exertion. Let’s examine the sit-up and the crunch to see which gives the better contraction to the 6-pack.

Sit up
  • Motion happens at the hips
  • Spine angle stays relatively the same
  • Spine flexes
  • Hip and all other joint angles stay stagnant

Through the lens of our two graphics, we can see that the crunch accomplishes our goal of spinal flexion for the rectus abdominis. While the sit up might provide a slight amount of spinal flexion, we can see that the majority of the motion comes through the hips. With load and large amounts of volume, this can actually be dangerous over time, as this motion heavily taxes the hip flexors which pull at the lumbar spine.

For maximal efficiency when training the rectus abdominis, it’s best to stick with crunches, as they are biomechanically the best way to contract the abs. I would recommend most start with something like 2-3 sets of 10-20 reps, focusing on controlling the entire motion, and exhaling all the air possible at the top of the motion.

Key Points

alex chris martin

Hi, I'm Alex, the founder of PTC. Hope you found this video helpful. If you need a coach for your goals, let's talk!

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