I felt 30 day arm challenge was the most effective of the three challenges that I did. I definitely felt the difference in my arms especially my triceps. I am thinking of doing this challenge again after Christmas and New Year.
I added lateral raises, front raises, narrow shoulder press and swimmers to the arm challenge (I know they are all shoulder exercises) but I did them with 2 lb weight and not 8 lb I was using for my arm exercises.
I also did the exercises in reps and as part of circuit without stopping. I would recommend this challenge to others.