Personal training pain

I have some connections with my job and one of my connections offered me a FREE personal training session this past week.  I guess the goal was to give me some tools that would help me with my running and give me some upper body strength. 

I met with the trainer and he had me doing all sorts of stuff. We started off with planks and slowly worked my back, chest, glutes, triceps and biceps. It was a pretty thorough workout. And I knew this because the next day I woke up and I could barely walk. 

Seriously - I used muscles that I never had before. I think that just because I run - I should be in spectacular shape. However, this workout proved me wrong. 

So my goal is to do these exercises once a week as a weight training session. Hopefully this will help me train my body in new ways for the marathon.