Flex5 by PetroFitness delivers sustainable, functional movement designed for healthy longevity. We blend flexible, personalized training with holistic wellness to fit your unique lifestyle. Move better, build strength, and achieve lasting vitality with a routine built completely around you.
What the Five in Flex5 Actually Stands For
Strength, conditioning, flexibility, nutrition, and spirituality. Those are the five pillars of the Flex5 Training Method, and the fifth is where this Uptown studio parts company with almost every other gym in Charlotte. Most training programs stop at four. Building a stated spiritual component into the methodology is what led co-founders Petro Martynyuk and Darla Lilleberg to structure the business as a fitness studio, yoga practice, and treatment clinic occupying the same 5,500 square feet rather than as three separate ventures.
A Gym, a Yoga Studio, and a Treatment Room in One Suite
The service list reads more like a wellness clinic than a gym. Alongside one-on-one personal training, HIIT, bootcamp, metabolic conditioning, yoga, and Pilates, the studio offers acupuncture, cupping, Rolfing, Reiki, massage therapy, infrared sauna, Ayurveda, and naturopathic consultation. Nutrition coaching runs through all of it as a standing pillar rather than an add-on package. For a member, this means a training session, a treatment, and a nutrition review can happen in one visit to one address, which is unusual anywhere and close to unheard of inside the I-277 loop.
Built Around the Uptown Workday
Everything about the operating model points at people working in the towers nearby. Flex5 sits in Suite 333 of the Charlotte National Building at 428 East 4th Street, next to the Hyatt, within walking distance of the Uptown office core. Doors open at 5:30 a.m. on weekdays and stay open until 7:30 p.m., bracketing a full working day at both ends. Corporate wellness programming for employer clients is a distinct line of business. Weekends run a shorter window, 7 a.m. to 2 p.m., but notably on both Saturday and Sunday, which many Charlotte studios do not offer. Sessions run by appointment rather than open access, and the studio also takes bookings through ClassPass.
Small Roster, Long Client Tenure
The review profile tells a specific story. As of August 2026 the studio holds a 4.9 rating across 71 Google reviews, with aggregators showing a 5.0 across roughly 117 reviews collected across platforms. The volume is modest by Uptown standards, but the tenure inside it is not: reviewers routinely describe multiple years of continuous training, and several arrived after cycling through trainers elsewhere. Recurring themes are programming that is planned rather than improvised session to session, form correction delivered by demonstration first, and group sessions scaled so that mixed ability levels can work the same circuit. Clients include marathon runners using the studio for cross-training during racing off-seasons.
Training That Leaves the Building
The most distinctive thing Flex5 does is not in Charlotte at all. The studio runs international yoga and fitness retreats, including trips to Costa Rica, where the same coaching staff programs multi-day itineraries built around morning training and sunset yoga. Participants describe them as the point where the five-pillar framing stops being a marketing structure and becomes the actual shape of a week. For a single-location Uptown studio, running its own destination retreats is a genuinely uncommon extension, and it explains a client base that stays put for years.
