Lower Back fatigue during Deck Squats

Is this normal?

To some extent, yes, high rep squats will fatigue you.

 

Couple actual issues I can think of offhand are;

- Rolling too far back over for your current flexibility into a candlestick, stretchin and tiring yourself out

- Sticking your butt out as you stand up, arching your back/APT

 

Without knowing more, for example whether your fatigue lasts, dissipates, comes on strongly, is accompanied by pain, or gives you issues in your other elements, yes, it's normal

What you are likely doing, is rolling onto your feet then arching up to standing instead of pressing up with your legs. That and tight hip flexors have been the two reasons I've seen behind any back soreness during deck squats.

Stretch your hip flexors, and when you squat up, focus on flexing your quads and glutes so that your legs are doing the work instead of your back. Your glutes likely aren't being used enough.