Hot answers tagged physiology
Basically, your body will start shutting down external systems (muscle control, digestion, etc) to preserve glucose to keep the brain ticking over. For a good example of this, look at the video of Gabriela Andersen-Scheiss (Then Gabriela Andersen) at the Olympic marathon in 1984. You can see that over the last lap, she has little control and keeps wandering ...
As noted by JohnP, there's not a lot of direct side effects at first, the effect being the result of your body routing energy to essential systems at the cost of others, but the effect is much like being drunk in that you lose coordination, reaction speed, and common sense. In much the same way that drinking alcohol sharply increases your risk of trauma, ...
I would stretch them out first and try to increase your flexibility. Maybe you are not recovering from your workouts sufficiently. Not knowing you, it is hard to hypothesize, but those are the only issues I can think of outside of an existing injury.
Only top voted, non community-wiki answers of a minimum length are eligible