Incredibly sore

[bigred869]

I used to work out 6 days a week and do cardio the 7th, but I have recently been very busy with college and work so I haven't worked out seriously in about a month. 2 days ago I went to the gym for 2 hours and intensely worked out my legs, back, shoulders, and biceps. Yesterday I was sore but today I seem even more sore especially in my forearm/bicep area and back.

 

[Joshua86]

What you're experienced is called delayed onset muscle soreness (DOMS).

Muscle Pain and Muscle Soreness After Exercise - What Causes Delayed Onset Muscle Pain and Soreness - DOMS