Bent Hollow Body Rock - muscle fatigue in mid back?

Newbie question here. I'll post a video as soon as I get a better connection. 

Im struggling with enduring through this exercise, but I'm not experiencing fatigue in my abs. I am experiencing rather surprising fatigue (even muscle failure) in my mid back, so much that I fail to complete the set. My instinct is to grab my shins so I can keep my body position (I'm aware that's 'nish nish' Bruno). 

What's oddis that the prior PE1 was so easy, and I can't understand why my mid back is so engaged  

Apologies for not having a video uploaded yet but perhaps this is something that another member has experienced

Thanks in advance 

Hi @Cuneyt Uysal, 

This is normal. It only shows imbalance in your core strength. I have experienced it too. Also remember that this is a Front Lever Progression you will find your middle back being 'engaged' more in the later progressions.  that is a good attitude that you have to keep your shape intact no matter what. please do follow up with your video for form check.

First time I did straight arm/leg HBHs I got some deep fatigue in mid back as well.  I went away by 3rd workout.

The reason of that is that the psoas muscles (hips flexor primarily) are much more stronger than abs (trunk flexors primarily). this also means that your are showing too much knees movement in order to perform the rocks, this increases the activation of hips flexor.

Hey thanks  for the quick reply folks, much appreciated. Really! 

Always good  to know I'm not experiencing something terribly unusual. As a rookie, it would be  really cool to have links to the Forum threads tagged with a specific exercise  directly from the PRO+ video lesson. I think you'd get more students complying as well