Senen “SLiM” Rodriguez is struggling through a head cold, but you’d never know it from his peppy voice and smooth delivery—a vocal art he’s perfected over 25 years on Denver airwaves. “I’m totally faking it,” admits Rodriguez, who has been awake for nine hours by our 2 p.m. chat.

He rises at 5:30 a.m. five days a week to spin Christian hip-hop and other upbeat tunes on the morning shift for Flo 107.1 FM. If his schedule occasionally requires a little feigned enthusiasm, his passion for his work is genuine. “My job is to bring the energy,” he says, “and I love doing things for my city.”

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For the past 15 years, Rodriguez’s civic duties have included hosting the Chihuahua races at Denver’s free Cinco de Mayo Festival, whose 37th iteration takes place May 2 to 3 at Civic Center Park. On the first day of the event, Rodriguez will take to the mic to pump up the crowd during the fierce competition, whose athletes bring a new meaning to the sports cliché of “leaving it all on the field.” “When you go Number Two on the course, that’s an automatic disqualification,” Rodriguez says.

As many as 100 pups (Rodriguez, the proud owner of rescue mutts Bacon and Wasabi, scrutinizes contestants in search of at least a little Chihuahua heritage) dash down grassy lanes during the event, which includes multiple heats across its preliminary, semifinal, and final rounds. In years past, the not-so-big winner has taken home a trophy, a basket of biscuits, and $500. Racers score style points with miniature sombreros, bandannas, feather boas, and even painted claws that flash in the sun.

“Let’s make some noise for Chica in lane six and Peanut in two,” Rodriguez will shout, before reminding everyone, human and canine, to stay hydrated in the heat. Despite the lighthearted vibe of the races, mortal peril isn’t unheard of. “There was the year when a hawk was circling over the course,” he laughs. “We were all like, ‘Keep an eye on those Chihuahuas!’ ”

Read More: The 6 Best Ways to Celebrate Cinco de Mayo Around Denver