Justin Whalen didn’t become involved with D1 Training as an entrepreneur looking for a concept. He became involved as a dad. Years ago, when his daughter’s volleyball coach suggested supplemental strength and agility work, he brought her to D1 Scottsdale. The moment they walked through the doors, something clicked.
“I thought, what would I have done athletically if I had something like this growing up.”
Justin played Division I baseball at the University of Portland and spent his childhood imagining a professional career. But the kind of structured strength training, speed work, and science-backed programming that kids have access to today simply didn’t exist. Watching his daughter thrive in that environment was transformative. He saw what D1 could unlock for athletes, and eventually, for adults as well. That experience grew into a calling, and today he owns D1 Training Arcadia, part of a national network of more than 90 locations facilitating more than a million athlete workouts each year.
“There’s an athlete in every single person on the planet. Lifting weights is easy. Being dedicated to the work is what’s hard.”
D1’s philosophy is rooted in athletic development rather than aesthetics. The structure mirrors the cadence used inside collegiate strength programs, which is why D1 hired a national panel of strength coaches to build their methodology. Every workout is programmed on a macro, meso, and micro cycle and every phase has intention behind it.
“Our programming rotates movement patterns and energy systems throughout the week, a structure used by high-performing athletic departments across the country. The goal is always progression without overstress.”
Muscles must be pushed, but they must also recover. Speed days. Agility days. Upper-body strength days. Lower-body strength days. It is a training architecture designed to create a complete, capable athlete rather than someone who simply looks fit.
“You need to stress the body, but in different ways, to get max output.”
This adaptability is part of what allows D1 to serve such a wide range of members. Professional athletes train beside adults who haven’t worked out in years, teens hoping to elevate their performance, and kids who are just beginning to understand movement. Every person begins with an assessment. Every person has different goals.
“No one body is the same and no one person has the same goals. Our programs are designed to meet each individual athlete where they are.”
According to Justin, youth training is one of the most misunderstood aspects of performance development. Many parents still fear weightlifting or worry about growth plates, but Justin stresses that D1’s age-based system is intentionally built around safety, science, and appropriate progression.
Rookies ages seven to eleven focus on the fundamentals: movement patterns, coordination, body control, and speed. Devos ages twelve to fourteen introduce light resistance with a strict form-first approach as their bodies adapt and grow. Once athletes enter the Prep program at fifteen to eighteen, they transition into true strength training with appropriate load, technique, and supervision. Justin emphasizes that the Prep structure intentionally mirrors what athletes would experience in a collegiate Division I program.
This tiered model aligns with National Strength and Conditioning Association guidelines, which show that properly supervised youth strength training is not only safe but enhances bone density, neuromuscular control, injury resilience, and long-term athletic development.
“Every phase is grounded in science-backed training methodology, supported by D1’s extensive database of athletes across all levels, from youth to pros. We teach fitness for life without overly stressing the body.”
Before strength becomes a priority, Justin says the emphasis should be on speed, agility, and nutrition, the foundations that build athletic capacity long before weights enter the picture. And beyond performance, he believes the single most important skill for youth athletes is time management.
“Balancing school, sports, family, and life is what prepares them for future success.”
On the adult side, the transformations Justin sees inside D1 are not just physical but deeply emotional. Men in their forties and fifties learn to train smarter rather than heavier. Women over thirty-five discover programming that supports metabolism, hormones, stability, and long-term strength. And for the average adult, something shifts far earlier than the numbers.
“Once you see that first drop in body fat or hit a lift you never thought you could do, everything changes.”
Women and moms represent one of D1’s fastest-growing membership groups, and the reason is rooted in both science and lived experience. After age thirty, women lose up to 8% of muscle mass per decade, a decline that directly affects metabolism, insulin sensitivity, joint support, and hormone regulation. Strength training two to three times a week has been shown to slow or reverse that loss by increasing lean mass, stabilizing blood sugar, and improving estrogen balance.
“It enhances bone density, which is particularly important because nearly 80% of osteoporosis cases occur in women.”
Athletic-style training is especially impactful for women over thirty-five because it stimulates several systems at once. Short bursts of speed work activate fast-twitch muscle fibers, which are essential for power and longevity but naturally decline with age. Resistance training strengthens the skeletal system by placing load on bones, a scientifically proven way to protect against fractures later in life. Interval work increases growth hormone and improves sleep quality, both of which become harder to regulate as estrogen and progesterone fluctuate.
The mental benefits are equally well documented.
“Research shows that strength training reduces anxiety, improves memory and focus, lowers stress levels, and increases overall wellbeing. Women begin trusting their bodies again. They learn proper form. They feel strong. They begin hitting numbers they never imagined possible.”
For moms, the structure of D1 matters. The class is already built. Movements are coached. Recovery is embedded. There is no guesswork. The goal is not to create elite competitors.
“It is to build resilient, functional, confident women who move through life feeling capable and strong.”
And perhaps the biggest surprise for newcomers is that athlete-style training is more fun and more accessible than they expect. The environment is energetic. The workouts evolve constantly. The programming meets each person where they are.
“There is a D1 athlete in every one of us. Time to go find it.”
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