Hi Chrissy
Here's a paper that has 1RM testing that includes the arm curl along with a detailed script on how to perform the assessments. I think it is worth reviewing if you're considering a 1RM assessment. The Effect of Single Set Resistance Training on Strength and Functional Fitness in Pulmonary Rehabilitation Patients
Phillips, Wayne T. PhD, FACSM; Benton, Melissa J. MSN, PhD, RN, CNS; Wagner, Carolyn L. BSN, RN; Riley, Cathy BSN, MBA, RN. Journal of Cardiopulmonary Rehabilitation 26(5):p 330-337, September 2006.