Three words of advice from fitness pros: Just. Keep. Moving.

“You’re doing great!” someone yelled from the sidewalk.

“You’re almost there!” another stranger told him.

The old man was the final participant in a 5k race near my home. The sun was setting. Most of the runners were long gone. The race equipment was coming down. People were returning home.

As the old man shuffled up the hill toward the finish line, I recorded a video of his determined effort. I posted it on my social media sites with the words, “Thirty seconds of motivation from a stranger.”

He perfectly illustrated the rallying cry that several fitness professionals keep telling me: Just. Keep. Moving.

“That’s the true secret,” Michele Stalion said.

She owns Fit Body Boot Camp in Valparaiso, which offered a six-week challenge in April with complimentary introductory sessions. I took advantage of this promotion to attempt a 30-minute High Intensity Interval Training workout with Sebastian Snyder, a trainer at the gym.

“Today’s focus will be unilateral strength and cardio,” Snyder told our group.

We went from station to station for just a couple of minutes. Each exercise was challenging in a different way, though each one was definitely doable. We alternated between intense bursts of activity and brief recovery periods, designed to boost metabolism and calorie-burn long after our workout ended.

“This keeps each boot camp workout engaging and effective, making the 30-minute sessions fly by as you’re constantly stimulated by new challenges,” the Fit Body website states.

It’s true. Thirty minutes flew by like three minutes.

A week later, my wife and I attempted a similar 30-minute workout at Fit Body Boot Camp in Chesterton. “Motivate the mind. The body will follow,” a poster on the wall states. (Watch videos of these workouts at NWI.com and on my Facebook page.)

Every workout participant, from out-of-shape beginners to trained professionals, encouraged newcomers at these sessions, offered throughout the day to accommodate work schedules and peak workout times (mine is mid-afternoon). I felt welcomed and comfortable, leaving just sweaty enough and proud enough to attempt it again.

With summer officially arriving this month, many of us are trying to become more active, whether it’s for health or vanity reasons. There’s something about wearing less clothing in warmer weather that always motivates me to get in better shape.

If you’re looking for a unique way to keep active, I suggest Rebound Babes, a fun, fast-paced and bouncy workout routine, hosted by Brittney Mossell, a rebound fitness trainer in DeMotte. The choreographed dance workout uses special shoes that feel like little trampolines on your feet.

“These boots relieve 80% of the impact on your joints, back, legs and hips,” Mossell said. “And you burn 25% more calories wearing these boots.”

The one-hour classes cost only $10 with discounts for multiple classes. (For more info, visit www.reboundbabes.com or her Facebook page.)

I’ve learned that the secret behind getting in shape or staying in shape is to vary your physical activities. Walking. Bicycling. Running. Strength training. Cardio workouts. Throwing a Frisbee at a park. Climbing every stairwell. Parking further away from a store’s entrance. Whatever it takes to keep moving and keep adding steps to your day.

Apple Watches are designed to do this for users by displaying real-time, personalized metrics to help motivate and congratulate every step, every activity, every hour. Medals, badges, closing activity “rings” — these kind of daily incentives work for many people. I don’t own an Apple Watch watch but I have friends who swear by them. (And sometimes swear at them.)

If you’re an outdoors lover, try climbing the Three Dune Challenge — the three tallest sand dunes at Indiana Dunes State Park. It’s 1.5 miles of tough trail with 552 vertical feet that’s 100% brag-worthy. If three dunes are too much, try one dune. If one dune is too much, try walking the beach. (For more info and a map, visit www.indianadunes.com.)

The whole idea is to do anything that holds your interest or offers a distraction or gets you off your butt. Over the past 40 years, I’ve attempted dozens of ways to keep me moving, from walking a few extra steps to the grocery store to running the Chicago Marathon. My knees hate me, but my heart loves me and my weight is kept under control.

It’s all about habits. One good habit gives an assist to another one. Before you know it, you’ve scored a triple-double through self-motivation, dedication and perspiration. The most challenging part of staying active for most people is simply getting started.

“The older you get, mobility becomes key,” said James O’Connor.

He and his wife, Tera, own and operate Team O’Connor Martial Arts & Fitness in Chesterton. He led me through a workout routine that focused on increased mobility and strength training. Before that, I had never considered the importance of simply retaining my body’s most basic movements.

“Keep moving forward,” O’Connor tells his clients.