Table 1 Definitions of risk situations and risk behavior during football matches.

Between-player physical contacts (duels) (as contacts per player-hour)

Total number of contacts excluding contacts to the lower limbs (duration and direction, frontal (face-to-face, i.e. collisions, scramble in anticipation of a corner kick/free-kick) or other direction)

 Upper body contacts: shoulder–shoulder, arm–arm, front–back, hand–jersey, hand–hand, hugging

 Head contacts: head–head, arm-/hand-to-head

Crowding during breaks (as contacts per playing-hour)

Gatherings of at least two persons (players or referee) within a range of less than about 1.5 m

Number of involved players and duration

 In free-kick walls

 While celebrating goals

 During breaks before corners/free-kicks

 During injury breaks

Aerosol and droplet producing activity (as number per player-hour)

Speaking or shouting (within a range of less than about 1.5 m), spitting

Within-player hand-to-head contacts (as contacts per player-hour)

Touching the own head with the hand, with or without touching a mucous membrane (mouth, nose, eyes)

Hand-/head-to-ball contacts (as contacts per playing-hour)

Before set-play: throw-in, corner, free-kick, goal-kick, kick-off, drop ball

During match play: kick-out, goalkeeper save (block or catch), header