Forearm Cramping

I haven’t really had this problem in the past, though recently I have been dieting and training a more. The problem is when I work my biceps and triceps I notice part way through the work out my forearms and elbow starts cramping a little, it prevents me from giving 'er my all.
Could anyone shed some light as to weather this cramping is normal? If so what can I do to stop it???

Magnesium oxide and Magnesium aspartate Calcium Glucinate