It happened between 4:15 to 4:30 p.m. in the area of 28th Street and Colorado Avenue.
Police say the man grabbed her from behind and put his arm around her neck.
The victim used pepper spray on her attacker at which point the man started hitting the victim.
The victim managed to get away after a brief struggle. The victim called police and received medical treatment at the scene.
The attacker is described as a white male. He was wearing a gray-colored, baggy sweatshirt with a dark blue or black knit stocking cap.
Investigators also want to question any potential witnesses. There were three bicyclists crossing the street in the area at the time of the attack.
Anyone with information is asked to contact Detective Jeremy Frenzen at 303-441-1890. Those who have information but wish to remain anonymous may contact the Northern Colorado Crime Stoppers at 1-800-222-TIPS (8477) or 1-800-444-3776.
(KUSA-TV © 2013 Multimedia Holdings Corporation)