NEWBURYPORT — Variety is the spice of life as Newburyport's Kevin Stehlin is well-aware.

At the age of 46, Stehlin, along with his wife, Sheila Brand, will be participating in the fourth annual Powow Triathlon being held at Amesbury's Lake Gardner, along with the Heat Triathlon Team. Heat founder, Heidi Thompson, said Stehlin, who not too long ago was content with his various routines of weight-lifting, yoga and spinning, has come a long way in four short years.

Stehlin began training with Heat in 2006, and though he was good shape, it wasn't conditioning conducive to endurance competition or a sprint triathlon (half-mile swim, 12.5-mile bike, 3-mile run).

"Since Heat's inception, Kevin has grown by leaps and bounds, and you can physically see it by looking at him," Thompson said. "He has grown leaner and stronger."

Four years ago, Stehlin was making his dues with lifts at the Fitness Factory in Newburyport. It was there that he met Thompson, who soon became his personal trainer. After mentioning the boot camp she runs at the Mall, Thompson told him how she also trains for triathlons. With a bit of nudging from Brand, and his own curiosity, Stehlin and his wife opted to give it a shot.

It would be different, Stehlin figured. A change of pace. After all, Stehlin had always considered personal fitness an integral part of his life; he had been an athlete in high school, and he played college football as a defensive back. He lifted weights, ran a bit and occasionally rode hybrid bikes with Brand.

But swimming, well, that was another story.

When he began swimming with the Heat team, Thompson could tell his skill level was eating at him.

"To say he wasn't a strong swimmer would have been generous," said Thompson, who is the Powow's race co-director with Andy Hawkes. "He only did the breast stroke, and he never kept up with the group; he would always be one of the last folks out of the water."

To his credit, Stehlin never quit, and his tenacity was evident. Thompson said that he always asked questions, remained open to suggestions and responded well to encouragement.

Steadily, Stehlin improved and progressed from basic techniques like the crawl stroke to bi-lateral breathing — taking breaths on both left and right sides, a useful skill when swimming in a pack of splashing athletes, or even in an ocean swell — and fine-tuned sighting, which is being able to look up quickly at an object and continue to swim in a straight line without having to raise your head again to see where you are; each time you raise your head, you slow down.

Though Stehlin and Brand have been training with Heat for the past two-and-a-half months, they both have been polishing their endurance with regular trips to the YWCA pool in Newburyport throughout the year.

Thompson also stated that Stehlin was initially a person who simply wanted to finish a triathlon, but he has evolved into a competitor she wouldn't be surprised to see place.

"Kevin has made a significant improvement in his transition, resulting in an improved overall time, and his running has steadily improved through consistency and efficiency of movement."

Two of the Heat team's initial 15 members — a myriad of new mothers, busy parents, singles, and athletes of every ability and size — Stehlin and his wife are now staples of the Heat team and have competed in all four Powow events.

Stehlin, who now has eight sprint triathlons under his belt, said that the introduction of Heat training and triathlon competition has made him a more versatile athlete, has aided in his swimming ability — a sport he may have never done otherwise — and uprooted some long-lost drive.

"I didn't realize how much I missed team athletics," Stehlin said. "How people push and root for each other, help one another to train and miss you when you aren't able to show. The people of Heat became a group of strangers who merged into a great team.

"And I never realized how I missed physical competition," Stehlin said. "At the end of the first race I did, probably with a quarter-mile to go, a guy and I challenged each other to finish, and after I finished the race, it just came to me that I truly missed physical competition."

With three kids in college and another in middle-school, both Stehlin and Brand already have their plates full, but it's the will to constantly improve that has Stehlin striving for the finish line.

"If somebody is in front of me, I'm trying to beat them or catch up to them," Stehlin said matter-of-factly. "Just like every triathlon, my goal is beat what I did last year by a minute, which should be pretty tough."