A native of Spruce Pine, North Carolina, Duncan attended Mitchell High School, where he excelled in wrestling, football, baseball, and track. Duncan was an all-conference lineman in football, a two-time state medalist in wrestling, and a wrestling state champion in 1988. He played a key role in the Mountaineers' team state tournament championship run in 1988 and was named Mitchell's male athlete of the year for 1988.

Duncan then attended Appalachian State University as a North Carolina Teaching Fellow, majoring in Social Science and Secondary Education. He was a two-year starter for the Appalachian Wrestling team and reached the Southern Conference finals at 190 lbs. in 1989. In 1993, Duncan completed his student teaching at Ashe County High School. In addition to student teaching, he helped coach the wrestling team, which finished as state runner-up. Duncan then taught social studies and coached wrestling at Hickory High School from 1993 to 2004. During his tenure at Hickory, he started a middle school wrestling team before returning to Mitchell High School in 2005. At Mitchell, Duncan also started a middle school program in 2006 and assumed the role of head wrestling coach at the high school in 2010. Duncan’s Mitchell teams have captured 250 dual meet wins, five conference championships, two regional tournament titles (2014, 2015), two dual team state championships (2014, 2015), one state dual team runner-up finish (2016), one state tournament championship (2015), and one state tournament runner-up finish (2014).

In 2004, Duncan became the first-ever Administrative Director for Team NC Wrestling. He served in this role until being elected State Chairperson for NCUSA Wrestling in 2018. He has been the National Teams Coach and the event director for the Elementary and Junior High State Championships. In 2013, Duncan founded and currently runs the High Country Youth League, which serves over 20 counties in Western North Carolina. He serves as a Junior Olympic Wrestling Committee member (2022 – present) and has directed the North Carolina State Games for over 20 years.

Duncan’s efforts have focused recently on building men’s and women’s beach wrestling and high school girls’ wrestling in North Carolina and across the country. He is the founding organizer of the first beach wrestling state championships and has hosted the USA National and North Carolina State Beach Wrestling Championships at Carolina Beach (2012 – present). He was the Team Leader/Coach for Team USA at the 2019 World Beach Games in Doha, Qatar, and has attended multiple world beach championships. Duncan is also the founder of the Beach Wrestling Tour of America (2022) and is the US Representative to the United World Wrestling Beach Wrestling Committee (2016 – present). Duncan was an organizer of the first girls' high school invitational, hosted the first-ever open state championship for girls (2017) and worked with the Women’s Wrestling Task Force to sanction girls high school wrestling in North Carolina (2023).

One of the original members and key organizers of the North Carolina Wrestling Coaches Association, Duncan served on the NCWCA Board from 2007 to 2014. He has also served on the Board of the state chapter of the National Wrestling Hall of Fame (2016 – present). Retiring from teaching in 2023, Duncan remains both the head wrestling coach at Mitchell High School and the State Chairman for North Carolina USA Wrestling. Duncan’s children Eve Duncan, Solomon Duncan, and Marie Murphy are all actively involved in the wrestling community serving in various roles.