OUR TEAM
Jack Oosten
Owner & Head Coach | B.S. Kinesiology, ACSM-EP-C, PPSC, CSCS, PN-1
Bio: Jack's passion for coaching lies in bridging the gap between the “science” and practical application which is a product of his lifelong interests in learning, sports, and training/nutrition. Jack has worked with a range of clients from ages 6-80 with a variety of different goals and circumstances, all with the end objective of helping clients achieve life-changing results by unlocking their inner badassery.
Specialties: Internal health restoration and optimization, injury rehab and prevention, bodybuilding, muscle growth, body recomposition, weight loss, fat loss, behavior change, integrative lifestyle coaching
Eileen Oosten
Co-Owner & Coach | B.S. Public Health, ACSM-CPT, NASM-CNC, AFPA-PPFS
Bio: Eileen is a mom of 2, NPC bikini competitor, former D1 athlete, and Coach at JackedNLeen. Eileen's passion for coaching stems from her own personal journey of lacking the proper education and resources to navigate her health and fitness goals during and after being an athlete, where she struggled with low self-confidence, poor body image, unhealthy eating habits, and depression for years. It wasn't until she hired her first coach that she discovered the confidence and empowerment that came from having the right guidance, knowledge and support as she worked toward her goals. Eileen strives to provide this same support to her clients today!
Specialties: Prenatal/perinatal/postnatal fitness, sustainable fat loss, women's weight loss, lifestyle behavior modification, nutrition coaching, bikini and wellness bodybuilding posing
Jack Stiele
Coach & Personal Trainer | CPT
Bio: Jack is passionate about helping others unlock their full potential through health and fitness. As a former JACKEDNLEEN client, he embodies the habits and lifestyle of a well-rounded, robust, and Harder to Kill (#H2K) human in his daily life. Driven by continuous learning and results, Jack's dynamic coaching approach focuses on building the right habits to help you chase excellence and achieve life-changing results.
Specialties: Weight loss, fat loss, strength gains, powerlifting, hypertrophy, bodybuilding, mindset/behavior change, injury rehab and prevention, lifestyle coaching
Dylan Mertz
Coach & Personal Trainer | B.S. Political Science, J3U L1
Bio: Born with Cystic Fibrosis, Dylan has never let his diagnosis be his excuse—instead, it became his reason to build discipline, resilience, confidence, and shift his focus to controlling the controllables in his health and life. Dylan is a true example of what it means to be JACKEDNLEEN and Harder to Kill (#H2K), and now he's on a mission to help others discover their strength, rewrite their limits, and become harder to kill in their own lives.
Specialties: Muscle growth, fat loss, strength & hypertrophy training, nutritional and lifestyle coaching.
Nick Larson
Coach & Personal Trainer
Bio: Nick combines evidence-based coaching with a practical, sustainable approach to achieving lasting results. Living with Type 1 diabetes, Nick leads by example, proving that your circumstances don't define your potential. His coaching philosophy reflects the JACKEDNLEEN Harder to Kill mindset: show up consistently, practice what you preach, and pursue growth with discipline, resilience, and integrity. Whether your goal is stepping on stage or becoming the strongest version of yourself, Nick is committed to helping you get there.
Specialties: Bodybuilding, weight loss, body re-composition, strength training
Peytton Bridges
B.S. Exercise Science, ACSM EP-C
Bio: Peytton is passionate about helping people discover what they're truly capable of. He believes fitness is about more than changing your body, it's a vehicle to build confidence, resilience, and habits that carry into every area of life. With a degree in Exercise Science and certification as an Exercise Physiologist, he empowers clients with the knowledge and technique to become the strongest version of themselves, both in and outside the gym.
Specialties: Fat loss, body re-composition, strength & hypertrophy, lifestyle coaching, men's fitness
Brooke Young
Coach & Personal Trainer | CPT
Bio: Brooke is passionate about helping people realize they're capable of more than they think. After losing over 90 pounds herself, she understands firsthand that lasting transformation comes from consistency, not perfection. Through supportive coaching, sustainable habits, and strength training, Brooke helps clients build confidence that extends far beyond the gym.
Specialties: Sustainable fat loss, strength training, habit & lifestyle change, confidence building, nutrition coaching
OUR MISSION:
To create well-rounded, robust, badass humans.
OUR VISION:
A world where all humans are JACKEDNLEEN, and Harder to Kill #H2K