His collegiate career was marked by a Division III record in the 800m at 1:45.83 and a 1500m best of 3:40.91, third all-time for the division. Symmonds turned professional in 2006, joining the Oregon Track Club Elite. His early professional success included a runner-up finish in the 800m at the AT&T USA Outdoor Track and Field Championships in 2006, a win at the Prefontaine Classic 800m in 2007, and securing the 800m title at the United States Olympic Trials in 2008. Symmonds continued his ascent in professional track and field, competing in the 800m semifinals at the Beijing Olympics in 2008.
Transitioning from competitive running, Symmonds co-founded Run Gum in 2014, a company that produces caffeinated chewing gum for athletes. He officially retired from professional track and field in 2018. Following his retirement, Symmonds significantly expanded his presence as a prominent YouTube personality, with his channel experiencing a surge in popularity around 2020. He consistently shares engaging content related to running, powerlifting, and general fitness, captivating a substantial audience on both YouTube and TikTok, further cementing his status in the fitness and adventure communities.
In a remarkable display of endurance, Symmonds embarked on his ‘Mile to Mountain’ project, aiming to climb the Seven Summits. This endeavor builds on his earlier athletic feats, including a personal best sub-four-minute mile of 3:56.72 set in 2007. In 2024, he successfully completed summiting all fifty U.S. state highpoints, concluding with Denali.
Most recently, in May 2025, Symmonds summited Mount Everest, an achievement that made him the first person to both run a sub-four-minute mile and reach the peak of Everest. As of May 2025, he has conquered four of the Seven Summits: Kilimanjaro, Puncak Jaya, Denali, and Everest, showcasing his continued exploration of physical and mental challenges.