Off cycle I have a hell of a problem pushing the reps I want as compared to on cycle.

Example.

On Cycle 10x10 training I get the 9th rep rush and finish up with mental power for 10th set. Example of this would be 185 lbs for military press.

Off Cycle I make 5x10 and my arms are completely dead in say the military press. Weight does not matter. Just repping 10x10 of the long bar is near impossible.

Is this a CNS thing (I would not think so) or a diet thing. I am a low carb type of guy.

I assume diet is diet but is working the 2a muscles too much causing no development of the 2b and resulting in this?.

I have no clue..any ideas are appreciative.