Vocal Function Exercises (VFEs) is a well-known treatment program that consists of four exercises, in which the first and fourth tasks require maximally sustained phonation. However, the active ingredients responsible for treatment efficacy are still unknown. The primary purpose of this investigation was the explore the effects of maximally sustained phonation on the VFE outcome measure of maximum phonation time (MPT) in individuals between the ages of 18-40 with normal voice. Participants were randomized into three experimental groups that completed VFEs for six weeks. The baseline group sustained tasks one and four for as long as was achieved at the baseline session; The three-week group sustained the exercises for as long as possible the first three weeks, then to their three-week MPT average for the remaining three weeks of the program; The standard group maximally sustained phonation for all six weeks. Results indicated significant improvement in percent to MPT goal attainment in the standard group and three-week group. The baseline group did not result in significant change. Including maximally sustained phonation throughout the course of VFEs is essential to producing substantial improvements in voice production, in terms of percent to MPT goal.