same location, characters in different places; how to slug?

I have several scenes in my screeplay where several characters are in the same location ... in different areas of that location.
in other words, i have a marathon race. i have a character running in it, a character watching her, a character talking with another character at the race ... etc.

so here's my Q
do i have to put a slugline to indicate WHERE the characters are within that same location? or can i just write the slugline ONCE and take for granted that the reader will know that they are all at the race ... in different locations ... together?

make sense?

Minislugs.

Write the slugline once. When you change locations, indicate that location on a separate line, then start in with the description.

Example:

EXT. STREET - DAY

Runners pick up the pace.

FRONT OF THE PACK

Kenyans take the lead.

SIDELINES

Spectators cheer.

BACK OF THE PACK

nickj stumbles and falls.

Something like that.