I've been lifting free weights three times a week since the end of February. I've also lifted on and off for the last four years (mostly off). I mean to stick with it this time. The weight lifting is part of an overall plan to lose body fat and have some strength for sports (tennis, volleyball, soccer).

This morning, I did a new exercise--concentration curls (sitting, legs spread apart, free hand on one knee, holding dumbbell with other hand with the elbow of that arm resting against the inner thigh). First set was 12 reps and I barely could finish the last one. I did eight the second set; the second-to-last one was hard and the last one I had to really struggle and it seemed to take forever to complete it. I could only do six the last set and again, I struggled to complete the last two (I mean grunting and yelling, etc.)

Shortly after, I felt discomfort in my biceps--I guess what they call the "burn." This is the first time I've ever felt this after doing any weight-lifting. 1) This is normal, right? I should feel this in all my muscles that I work? 2) Did I accomplish nothing in all the times I've lifted weights in the past and didn't feel this burn?

Thanks.

I usually associate a burn with, say 8+ reps, and i say usually.

When i use high weigh low reps (which is unusual lately) i dont feel it. But yea i usually get a burn. Iv also noticed it depends how tired i am to how much i get that feeling. That makes sense tho, as youll obviously fatique faster if your more tired.

Anyway im going away from the point

And only you can tell us if you accomplished something during your time in lifting. Just be cause you dont feel a burn, doesnt mean to say the muscle isnt being worked.

In the past, did you lift to failure? Meaning that you couldn't complete another rep, even though your muscles didn't burn.

No; I could always complete another rep. Does this mean I wasn't really strengthening the muscle?

You want to be struggling on roughly every last rep. If not the weight is too light. You should be lifting heavy!

Right. If your body can handle the weight no problem, your brain is going to believe that your body is the right size to handle the job. If you force your body to lift weight that is a little too heavy, your brain will realize that it needs to build muscle to handle the heavy weights.