The athletes, barking steadily, strained against their leashes toward the racing field. Their trainers, clad in team T-shirts, made final preparations: Do I have the string cheese in my pocket as a finish-line treat? Do I have his favorite toy? Are his paws taped properly?

Soon, the first dog on each team was off-leash and running: leaping four hurdles, tapping a spring-loaded box to release a mouth-sized ball, grabbing the ball and dashing back over the hurdles with it.

Flyball, a sport in which four-dog teams compete in a carefully choreographed relay race, is becoming a weekend ritual for many people, as sacrosanct as youth soccer or bowling leagues are to others. Steve Corona, chairman of the North American Flyball Association, said the sport has around 700 clubs around the country — including the Twin Cities — with 16,000 registered dogs.

Aside from the occasional ribbon, trophy or title that its recipient cannot fully appreciate (“Iron Dog”), the main rewards are the sense of community that flyball fosters and — perhaps more important — the emotional partnership it builds between people and their pets.

“Once you work with a dog, that bonds the two of you to a whole other level,” said Dr. Peter J. Lotsikas, a veterinarian and founder of Skylos Sports Medicine of Maryland, which specializes in treating orthopedic problems in dogs. The shared activity makes both species happier and healthier, Lotsikas said. “When you are really trying to accomplish a goal, there has to be a higher level of communication there — it’s amazing once you feel it click.”

Flyball is the only sport in which the dogs are allowed to bark as freely as they want, which brings joy to the dogs (and prompts some spectators to don earplugs).

“Once a dog has a job rather than being just a pet, they just love it so much,” said Kerry D’Ascoli, a dog groomer from Laytonsville, Md., who was racing her Boston terrier, Bertha, at the tournament. “It’s a special bond.”

Flyball, which traces its roots to the late 1960s in California, emerged as an organized sport in the 1980s after the inventor of the spring-loaded flyball box demonstrated it on “The Tonight Show” with Johnny Carson. The North American Flyball Association was founded in 1984, and from there the rules took shape: A regulation flyball course is 51 feet long, with 2-foot-wide hurdles spaced 10 feet apart. Dogs must clear all the hurdles and reach the finish line with their ball still in their mouths.

Flubs are frequent. At this tournament, several dogs dropped the ball before reaching the finish line, and some ran outside the hurdles or knocked them down. Part of the training regimen involves teaching the dog to ignore distractions.

Dogs of all sizes can compete. The flyball rule book — which runs 128 pages — dictates that the hurdles can be set from 7 to 14 inches high, as determined by the height of the shortest dog on the team from the ground to the withers. Dogs are measured on race day.

Some dogs learn quickly, but others need more time. The trickiest steps include introducing the ball (after a dog has learned to jump the hurdles) and teaching the dog to do a “swimmer’s turn” at the box, so that it grabs the ball gently and doesn’t slam into the device.

Flyball does not appeal to all dogs, said James Serpell, a professor of animal ethics and welfare at the University of Pennsylvania School of Veterinary Medicine. For these dogs, taking a walk, running off-leash or chasing a ball or a Frisbee can have similar health benefits, he said.

“If your dog enjoys that sort of activity, it’s tremendously good for them, and it will make your life happier, too, because when your dog is at home he or she will be calmer and less of a nuisance,” Serpell said.