The #1 “hot spot” for aggression inside a nightclub is on the dance floor, researchers have found.

According to a recent study, about 20 percent of the most harmful incidents occurred on a bar’s dance floor, and another 13 percent occurred nearby.

“There’s a lot of sexual aggression and aggressive horseplay on the dance floor in late night, large-capacity bars and nightclubs,” says study author Kathryn Graham, a senior scientist at the Centre for Addiction and Mental Health in Toronto, Canada.

Researchers visited more than 100 different clubs with at least a 300-person capacity on Friday and Saturday evenings between midnight and 3 a.m. They made over 1,300 visits over a two-year period. Their findings were published in the journal Drug and Alcohol Review.

Reasons for the dance floor focus may be numbers-based: it is usually the most crowded area of the nightclub, which may trigger more fights. The study also found the second-most common area for bar fights was the area near the serving bar, with tables coming in third.