About

Dr. Claire Rathjen is the Co-Founder and Owner of C.O.R.E. Physical Therapy and Sports Performance in Omaha, NE. She earned her Doctorate in Physical Therapy from Creighton University in 2008 and has since built a career specializing in sports performance, rehabilitation, and athletic populations.

Dr. Claire is an accomplished strength athlete and continues to compete in powerlifting at both the state and national level. She currently holds multiple Nebraska state records in the 105 lb and 114 lb weight classes and actively trains competitive athletes in strength sports.

In addition to her clinical work, Dr. Claire serves as an Adjunct Faculty Professor at Creighton University Medical Center, where she has lectured on topics including dry needling, sports performance, research, and kinesiology for athletic populations since 2016.

She is certified in dry needling through the Myopain Institute and integrates this treatment into her physical therapy practice. Dr. Claire is also fully certified in medical bike fitting and has over 13 years of experience incorporating bike fit assessments into patient care. Her expertise in slow-motion gait analysis for runners is a key component of her comprehensive sports rehabilitation approach.

Outside of the clinic, she enjoys running, triathlons, traveling, and strength training. She is also a passionate cat lover and co-owns CORE alongside her husband and best friend, Dr. Mark Rathjen, where they work side by side to deliver exceptional physical therapy and sports performance care in Omaha.

Dr. Claire is dedicated to helping patients and athletes recover from injury, improve movement efficiency, and perform at their highest level through detailed, individualized treatment plans.

Dr. Mark Rathjen is the Co-Founder and Owner of C.O.R.E. Physical Therapy and Sports Performance in Omaha, NE. He is a Doctor of Physical Therapy (DPT) and a Certified Strength and Conditioning Specialist (CSCS), with a strong background in sports performance, strength training, and rehabilitation.

Mark grew up in Lincoln, Nebraska, and attended the University of Nebraska–Lincoln, where he competed on a club powerlifting team in various local and regional competitions. His passion for human performance, exercise science, kinesiology, and injury prevention led him to Des Moines University Medical Center, where he earned his Doctorate in Physical Therapy in 2006.

With more than 25 years of experience in weightlifting, powerlifting, Olympic lifting, and sports performance training, Dr. Mark specializes in helping patients and athletes move efficiently, train safely, and reduce the risk of injury. He has an extensive background in martial arts and continues to maintain an active lifestyle through strength training, Olympic lifting, and outdoor endurance activities.

At CORE Physical Therapy in Omaha, Dr. Mark focuses on movement analysis and performance optimization, including slow-motion gait analysis for runners and detailed biomechanical assessments for weightlifting technique, bar path, and movement mechanics. His goal is to help each patient improve form, reduce overuse injuries, and perform at their highest level.

He also provides individualized strength and mobility programming, including Olympic lifting and powerlifting instruction, corrective exercise, and movement training tailored to each patient’s body, goals, and abilities.

Outside the clinic, Mark enjoys traveling, trying new foods, staying active, and spending time with animals—especially his cats. He is proud to work alongside his wife and best friend, Dr. Claire Rathjen, as they continue to build C.O.R.E. Physical Therapy and Sports Performance as a leading physical therapy clinic in Omaha.

Dr. Taylor Feenstra is a physical therapist at C.O.R.E. Physical Therapy and Sports Performance in Omaha, NE. He earned his Doctorate of Physical Therapy from Des Moines University, along with a Master’s degree in Exercise Science from Wayne State College and a Bachelor’s degree in Exercise Science from Dordt University, where he was also a varsity basketball player and NAIA Scholar-Athlete.

Dr. Taylor brings extensive experience in sports rehabilitation, orthopedic physical therapy, and post-surgical recovery. His clinical approach focuses on patient education and identifying the root cause of pain and movement dysfunction to help patients achieve long-term results.

He is a Certified Strength and Conditioning Specialist (CSCS) and a USA Weightlifting Coach, with a strong background in strength training and athletic performance. Outside the clinic, he is also an accomplished powerlifter and competes in jiu-jitsu at both national and international levels.

In addition to his clinical work, Dr. Taylor has coached collegiate strength and conditioning programs and served as a professor, helping educate future professionals in exercise science and human performance. He incorporates evidence-based techniques such as dry needling, trigger point therapy, and advanced manual therapy to optimize recovery and performance.

Dr. Taylor is dedicated to helping athletes and active individuals in Omaha return to sport, improve strength, and move with confidence through high-level, individualized physical therapy care.

Jadyn Ostrand “JJ” is the Marketing & Business Coordinator at CORE Physical Therapy and Sports Performance. She plays a key role in supporting the clinic’s marketing initiatives, billing processes, administrative operations, and overall front office management.

JJ previously spent two years at the front desk, where she built strong relationships with patients and guided them through their care experience. After rejoining the team, she transitioned into an expanded role that supports multiple areas of the business. Known for her outgoing and approachable personality, JJ is passionate about creating a welcoming atmosphere and ensuring every patient has a seamless experience from start to finish.

Outside of the clinic, JJ enjoys spending time with her fiancé and their two dogs, Alfie and Ada.

Sheila Wageman is the Patient Coordinator at CORE Physical Therapy and Sports Performance. She supports the front office with scheduling, patient communication, and day-to-day administrative tasks, helping ensure a smooth and welcoming experience for everyone who walks through the door.

She brings over 25 years of clerical experience to the team, along with a Bachelor of Science degree in Education with an emphasis in Therapeutic Recreation. She enjoys getting to know patients and helping them feel comfortable and supported throughout their time at CORE.

Outside of the clinic, Sheila has been married for 24 years and is a proud mom of two children. She also loves spending time with her dog. In her free time, she enjoys traveling, watching movies, and making the most of her favorite season—summer.