Jittery after workout

Hi y'all,

Anyone else get jittery after a workout?  I finished upper body today and got really jittery.

What causes this?

I get this after the stretching series when I'm going hard for more range of motion, I'm guessing its fatigue of the nervous system but i could be wrong.

Possibly low blood sugar, might be worth checking that out.

Those were the two answers that I had in mind along with not enough food. I'm pretty sure it's not lack of food though, as I always eat an hour or so before I work out. 

I will check my blood sugar just to make sure.

I did move up the reps this week in two of the three exercises in upper body so it could well be neural fatigue. 

Thanks for the help Philip and Stef.