CrossFit Armati Coaches

Our experienced, safety-focused coaches offer you the very best in motivation and training, pushing you to redefine your limits while reconditioning your body and mind. They’re well equipped to help you pump up your intensity and recondition your mind and body. Our friendly, growing CrossFit community will meet you where you are, and inspire the confidence you need to keep going. You’ll love the personalized support you receive at every level!

Derek Grenfell

Founder & Head Coach

Owner/Coach Derek Grenfell has been CrossFitting for five years and specializes in weightlifting and nutrition. He’s passionate about creating stronger, healthier people that are “harder to kill”—a phrase that comes straight from his favorite quote from Mark Rippetoe: “Stronger people are harder to kill than weak people and more useful in general.” He loves seeing the moment when members realize they are in the driver’s seat of their own health and fitness, and knowing that they can get as far as they are willing to go.

Derek has spent most of his early life wrestling, competing at the national level several times, and discovered CrossFit while he was in chiropractic school. “It immediately challenged me and humbled me,” he says. “It wasn’t long before I was back in similar shape to my old competition days.” As he began working in his own private practice, he spent a lot of time addressing functional rehabilitation, but had nowhere to send patients once they were discharged from his care. The answer was obvious. “I had to open a CrossFit box as soon as possible, so that the patients I was working with had a place they could get after it and continue to increase their fitness utilizing functional movements.” Since Derek already had a background in coaching and training, he applied to a gym that was converting from regular group training into a CrossFit affiliate. What started as a part-time job to pay the bills while studying, became an absolute passion and he hasn’t looked back since.


CrossFit Level 1 Trainer
Performance and Corrective Exercise Specialist
Doctor of Chiropractic

Brandon Schopf


Coach Brandon Schopf is passionate about improving the general wellness and fitness in his community. Before becoming a CrossFit coach at CrossFit Armati, Brandon served as a Door County paramedic for 15 years. But seeing what some people are forced to go through on a daily basis because of their unhealthy lifestyle is something Brandon wants to help with. He says, “Through CrossFit Armati, I can help people with fitness, nutritional and motivational information, Hopefully improving their overall physical wellness before they have to use services like paramedics, in home or out of home care.”

Brandon has always felt the need to be fit and healthy. “I have spent the last 10 years trying everything from running to weightlifting to HIT workouts.”, luckily on his road to fitness he ran into Coach Derek, who piqued his interest by telling him he was opening a CrossFit gym and he hasn’t looked back since. Brandon’s favorite quote is from Jim Rohn and it says, “We all must suffer from one of two pains; the pain of discipline or the pain of regret. The difference is discipline ways ounces while regret weighs tons.”



Jamie Kasten


Coach Jamie Kasten has been CrossFitting since January of 2018 and comes from a background of obstacle course racing.  She is most passionate about continuous learning, healthy living, horses and her most recent interest, downhill skiing.  As a coach at CrossFit Armati, she loves watching someone improve and succeed, but perhaps even more she loves learning something new from different athletes every single day. Coach Jamie feels fortunate to be surrounded by those dedicated to continued learning, improvement, and growth and that inspires her to continue to grow and learn in her own life.

Prior to her time at CrossFit Armati, Coach Jamie played soccer throughout high school, and started running in my free time in college. She ran an ultramarathon (32 miles) 5 years ago. In 2016 she attempted to run her first Spartan race in Killington, VT, got disqualified, and was more motivated than ever to improve.  She has run competitive Spartan races ever since and during the summer of 2018 placed second in her age group at the Spartan Sprint course (4 miles) in Garrettsville, Ohio. She missed third place the day before by minutes (14-mile course) and decided to try one more time.  

Coach Jamie decided to become a coach because CrossFit has changed her own life. She had tried CrossFit previously and didn’t like it but was drawn to CrossFit Armati upon moving back to Sturgeon Bay from Maine. It ended up being the best environment she could put herself in, allowing her to lose weight, run faster, lift heavier weights, do her first pull up, place in a competitive Spartan race, and meet some of her best friends. The people in this gym were all catalysts in some way to her. She says her goal as a coach is to be a catalyst for others.  Coach Jamie’s favorite quote is from Bruce Mau’s “Incomplete Manifest for Growth” It is point #32, “Listen carefully. Every collaborator who enters our orbit brings with him or her a world more strange and complex than any we could ever hope to imagine. By listening to the details and the subtlety of their needs, desires, or ambitions, we fold their world onto our own. Neither party will ever be the same.”

Certifications: CF-L1, RN, BLS/CPR, ACLS, PALS


Jennifer Vandertie


Coach Jennifer Vandertie finds passion in anything that makes one better today than they were yesterday.  Of course, CrossFit does just that.  Jennifer carries this passion outside the gym as well.  Coach Jen is currently a sophomore at the University of Wisconsin – Green Bay and when she’s not busy studying, coaching or working she spends time volunteering with several local organizations.  

Coach Jen has been with CrossFit Armati since January of 2018 and her favorite thing about coaching is being able to witness just how far members will push themselves.  She knows that each person is capable of so much more than they realize at the beginning.  She loves helping them “unlock” their potential through CrossFit.  Members of the Armati Tribe have a lot of grit and inspire her to be better than she was a day ago, a month ago, or even years ago.  

Prior to joining CrossFit Armati, Coach Jen ran track and cross country in high school.  She went to state for the 4×800 meter relay twice, set school records for the 400 meters and 300-meter hurdles and was voted MVP her senior season.  However, it was CrossFit Armati that really stoked her athletic fire.  As soon as she set foot in this gym, she immediately felt drawn to it and never wanted to leave.  Once hooked, she realized this was a path she aspired to pursue at a deeper level.  Jen wanted to deepen her knowledge on movement and fitness in general but more importantly, be able to advocate her knowledge to those around her. Upon attending the Level 1 Certification course, she realized this was exactly what she was looking for. Jen’s favorite quote is from Thomas Edison and it says, “If you want something you never had, then you have to be willing to do something you’ve never done.”

Certifications: Certified Level 1 CrossFit Trainer

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