Shirden attended both St. Joseph's High School and Cheshire Academy in his high school years. In his high school career, he rushed for 5,529 yards and totaled 107 career touchdowns. He was not very highly recruited and chose to join Monmouth.
As a freshman in 2021, Shirden played in 11 games, making 3 starts. He tallied 497 yards on 77 carries with 3 touchdowns.
His sophomore season was his first as a starter, and he took the FCS world by storm, exploding for 1,722 yards and 13 touchdowns on the ground. He had nine 100-yard games and four 200-yard games.
His junior season in 2023 was another impressive season as he rushed 221 times for 1,478 yards and 10 touchdowns. He also added 20 receptions for 123 yards and a touchdown.