after several months of regular cardio and running I’m now starting to train my upper body, basically planks and working out with a dumbbell. I’m tall and skinny, so I never had much fat or muscle mass in my arms.

I’ve trained my arms for 3 days in a row, nothing fancy: upright rows, bent-over rows and triceps kickbacks, 10 repetitions each, 2 rounds.

After that I’m so sore I cannot do more, so I turn to cardio and do planks (front and side) and some yoga.

Today, fourth day, I’m not in the mood to tone up my arms because they burn, but should I keep exercising? Doesn’t the burn mean muscle is being built?

I also don’t know if I should work with my arms less than with my legs, should I do cardio and running 5 times a week and arm toning only 3? Would it be better to do both in the same session or to alternate (odd days cardio and running, even days arm toning and yoga)?