A man wearing a lacy body suit exposed himself at a woman in Sheffield.
He struck near to the field opposite the Ridgeway Arms pub in Mosborough on Monday afternoon.
The Killamarsh Kestrels Running Club alerted its members to the incident and warned them to avoid running alone in the area.
In a Facebook post, the club said: "The mother of one of our members, also a runner, has been approached by a white male in his early twenties, wearing a white zipped jacket with dark hair combed forward.
"After asking explicit questions, he unzipped his jacket to expose a black lace body suit.
"The incident occurred near the horse field opposite the Ridgeway Arms on Monday afternoon.
"We would ask all female runners to avoid running alone especially in this area."