I’m going to tell you a couple of things about me that not all fitness trainers will tell you.

I never played sports in high school, I despised running a mile in gym class, and I have never been coordinated enough to excel at step aerobics or anything that requires a lot of rhythm or grace. I have always had to work HARD for things that come easy for some. I don’t say this for pity or as an excuse. I say this because it makes me a better trainer. I will never ask you to as a client to do anything that I wouldn’t or couldn’t do myself. Some trainers don’t have any clue what it’s like to be a “normal person,” (whatever that definition means anymore,) but I know what it’s like to struggle to find your fitness or to get your fitness back, because I’ve been in BOTH of those predicaments. It’s hard and sometimes you just need to take a deep breath and ask for some accountability from someone who will push you more than you feel willing to push yourself.


Nikki Mueller, owner of Healthy Girl Fitness, LLC

  • Certified AFAA Group Fitness Instructor
  • Certified RRCA Running Coach
  • Certified VDOT Running Coach
  • Certified USA Fit Running Coach
  • Race Director
  • First Aid/CPR Certified
  • Background in Pre & Postnatal Fitness Training


When people find out you’re a personal trainer, a fitness instructor, a running coach, or really anything in the health industry, there is a lot of assumption about the kind of person you are. I know this because I had some pre-conceived notions about trainers when I joined a gym in my 20’s at the lowest point in my life. My trainer was blonde, tan, fit, and bubbly. She was all the things that one would imagine a personal trainer to be, and she was amazing at what she did. Despite the fact that she seemed like the girl in high school who would never talk to me, I did what she asked of me, grew to trust her, and she made incredible things happen for me.

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When I started my fitness journey, I was overweight, depressed, and my confidence was at an all time low. I am grateful every day for being brave enough to step into that gym all those years ago because everything in me was terrified. I remember all the eyes on me in my cheap, cotton sweatpants and I was worried about the judgement that others would place on me. But I was ready for a change, and I decided that day that I was going to hire someone to help me take control over my life and I was going to do every single thing she told me to, because I didn’t want to waste my time or my money. And magically, it worked and I lost 80 lbs in a year by eating better and working out.

I also started running, and at first I couldn’t do a lap around the parking lot without getting horrible side cramps because I didn’t know how to breathe correctly. But I started with 3 minutes of walking on the treadmill and 1 minute of running, over and over. Then I gradually increased the running time and found myself able to run 3 miles. From there, I got up to 6 miles, then 10. I did my first half marathon in 2005 and my first full marathon in 2006. I ran 3 more marathons before getting pregnant.

Then I had kids. Though every pound I gained was worth the joy they brought me, I felt like my body had betrayed me. The things that had gotten easy were suddenly hard again. Doing 1 push-up was a challenge and I felt completely defeated. I was sleep deprived, emotional, and weak. I didn’t have the time or the energy to care for myself and I felt as though I was at the bottom of a hole with no shovel. When I finally looked up and saw the sunshine at the top of that hole, I decided to start digging in the dirt with my hands, so to speak. And with the support of some awesome other mommas, I clawed my way out. I found myself able to run short distances with the stroller and take less and less walking breaks. I saw my arms getting stronger and my clothes fitting better. Eventually, I was able to run marathons again, and I found myself faster than I’d been before kids. Things began to happen. All it took was time and putting one foot in front of the other every single day. I challenged my body over and over again. It was hard, but it was possible. I found myself in the best shape of my life. Ever.

After years of pushing myself to these limits, I came to the realization that I had some knowledge worth sharing with others. There are so many people out there who just need someone to believe in them and to guide them down the right path. Despite the fact that I was NEVER that person who stood up in front of a group, I got my AFAA certification a few years ago and started training pregnant and post partum moms as a group fitness instructor. And then I got certified by the RRCA to be a running coach too because I figured it was time to help others scale all those hills I’ve been running for so many years. I’ve had a lot of devotion to running and fitness because, quite frankly, it saved me.

I'm not here to "sell" you on anything. I'm not here to brag about my accomplishments either. I just want you to know that I've been there. I know how hard it is. I want to help others because I couldn't have done it without the help of others myself. I was terrified to put myself out there in the beginning, but I'm glad I did and I just want others to give it a try too. I've got some credentials, but it's honestly it's the life experience that I depend on to make me a good trainer. 

So if you want experience, I’ve got it. I have taken years of classes: boot camp style, spinning/cycling, kickboxing, yoga, barre, and just about everything in between. In addition to this, I’ve run dozens of half marathons, 6 full marathons and counting, more relays than I can count and every other distance under the sun. I’m now running ultras and digging deeper than ever. I write for a running blog called “Run Oregon” and I get to test running gear and run more races than I ever thought possible. I’ve been on every side of the fitness game, from sitting on the sidelines embarassed to active participant, and finally to encouraging leader. I’ve even taught classes and then taken my classes taught by other instructors because I want to experience everything my clients do. I have been in this business in one way or another for over a decade. I’ve been around the block and I can show you some things if you let me try! 


I’ll meet with you for a half hour consultation to see if we’re a good fit for each other and to find out what your goals are. I offer the following services:

  • One-On-One Personal Training: You’ll get customized full-body workouts that focus on both strength and cardiovascular training. You will primarily use your own body weight and some resistance bands for the majority of the exercise sessions, so fancy equipment is not necessary.
  • Partner/Group Training: Have you ever had an accountability partner? Find some friends who want to join you and I can train you all for a more cost-effective option that’ll be fun as well as challenging. Similar in style to the one-on-one personal training, you'll get a full body workout with both strength and cardio training with friends!!
  • Run Coaching: Whether you’re looking for 1 session or ongoing training, I can help you accomplish what you’re looking for to get you ready for a race or just to feel stronger running around your neighborhood.
  • Group Run Coaching: Everything is more fun in groups, especially running! Have a friend or a group of running buddies do it with you and it’s like a weekly “friend date” except sweatier.
  • Customized Plans: Are you training for a specific race? Trying to transition from one distance to another? Wanting to reach a new PR? I can build you a plan to get you there!
  • 8 Week Run Training Program: My goal is to offer Fall, Winter, Spring, and Summer series sessions to get you race ready or just to have fun out there running with other like-minded people. This will be an hour long class that meets once a week for 8 weeks and will cover things like speed work, hill intervals, and other tools to make you a stronger runner.
    • WINTER SERIES!!! Choose your own adventure:
      • Wednesday nights January 30th thru March 20th from 6:30PM to 7:30PM at Oregon Episcopal School track (6300 SW Nichol Rd)
      • Thursday mornings from 9:30AM to 10:30AM from March 31st through March 21st at Vista Brook Park )6697 SW 88th Ave)


I can come to you! I have some clients with small children and it’s just not feasible for them to go to a gym and have to find childcare, so I’m willing to come to their homes and train them while their little ones sleep or play. I also have a studio available to me if you're not sure where to meet, though availability is limited. I’m also happy to meet up with you at a park or another destination of your choosing. Gym equipment is not necessary, so consider me your mobile trainer. 

Please note that I live in SW Portland, and I have some time constraints in regards to traveling too far. I prefer to work in the SW Portland/Beaverton/Tigard area, but feel free to contact me to see if we can work something out.

Currently, I also have this option available (as seen on the "What" tab):


  • Wednesday nights January 30th thru March 20th from 6:30PM to 7:30PM
    • Oregon Episcopal School track (6300 SW Nichol Rd)
  • Thursday mornings from 9:30AM to 10:30AM from March 31st through March 21st
    • Vista Brook Park (6697 SW 88th Ave)


Strength and cardiovascular training are what I offer as a personal training instructor. I believe in doing whole body workouts rather than "leg day" or "arms day" workouts because I realize we have busy lives and we want it all. All of the workouts I plan are with resistance bands and body weight, so they can easily be done at home or on vacation without the need for fancy gym equipment. 


As a running coach, I can train you both on a track and off. If you are looking for a hill workout, I'll take you there. If you want speed, we can do that too. If there's a specific race you are training for, let me know and I'll create a plan and work it around your schedule. If you are looking for a group to run with, I've got 8 week training sessions every season as well as weekend options for you to find people to sweat with. 

I’m here to help you reach whatever goals you have, as your happiness is my ultimate objective. All my workouts are totally customizable to your needs. 

My style is fairly laid back. My philosophy is that I’ll make you work as hard as you want to. If you want to put in the work, I’ll bring it. If you want to dial it back, I’ll help make that happen too. Ultimately, it’s YOUR workout, so you put in what you want to get.


It hasn’t been about being skinny for me in a long time. By the time I hit the age of 40, I knew that I no longer cared about fitting into cute size 2 jeans. I just wanted to feel good, healthy, and comfortable in my skin. That’s where the “Healthy Girl” creation came from, because that’s what I believe in. I knew I wasn’t alone and that I could help men and women out there who needed someone to offer them encouragement and support in a safe, judgement-free zone.

As cliché as it sounds, I started Healthy Girl Fitness because I truly want to help other people reclaim their bodies and their confidence the same way I did. I want to improve the lives of people who are willing to work for it. I spent so much of my life overweight and unhappy and I gained so much in taking control of my body. I want to help others achieve the same thing. Ask any of my clients or my friends and family and they will all tell you the same thing: I am passionate about this.

You think you can’t do it, but you just need someone to help prove that you CAN. And you WILL!!


Nikki is truly an amazing trainer. She has the perfect combination of passion, drive, and commitment to her clients. She knows just how to motivate and push, as well as offering encouragement throughout. Her professionalism, knowledge, and diverse training methods are the perfect scenario to achieve success and set a great foundation for a healthy lifestyle. She has my highest recommendation.  

- Mindy

Highly recommend!

After my second child my core muscles were non-existent and I couldn't seem to find time to exercise. Then I ran into Nikki. As a mom, Nikki knows what areas I need to work on and what exercises it will take to get back in shape.  She formulates workouts based on my needs and gives me homewok to help keep me on track. She is flexible and able to work with my busy schedule. My mental state, physical strength and endurance have all improved since I started working with Nikki. 

- Karen

Training from a mom to a mom

There are not enough wonderful things I can say about Nikki Mueller and her training. I have taken both strength training classes and running training with Nikki and her subtle motivation flows throughout all fitness ventures. She is truly the "lead by example" type of trainer. Nikki's whole life is about bettering herself physically and creating a life worth being proud of, and that inspires me, everyday to get up and get moving! She motivated me through passively watching her live her fitness lifestyle to the fullest as well and actively, when she is pushing my to go "just one more mile"!


Glowing Review for Nikki's Training

Nikki is one of the most positive and motivating instructors I've had. While she is gentle and encouraging by nature, her workouts are rigorous and challenging. Nikki has high expectations for herself and those she instructs and her vast knowledge and personal experience guide her instruction. 

- Karin

Group Exercise Instructor Recommendation

Recent News

The Journey

You never know what someone else’s journey is, or where it’s taking them. You’ve heard that you should “never judge a man until you’ve walked a mile in his shoes.” Maybe it has no meaning to you because you’ve heard it so many times, but it’s so true.

After I had my first son, running was difficult. Not only was I not getting any sleep and feeling sluggish all the time (to put it mildly!) my body didn’t seem to know what to do anymore. I felt all put together wrong. I was breast-feeding and to even consider running meant a lot of planning and timing everything just right. Sometimes it didn’t seem worth it for a short run, especially when I had to walk so much. Sometimes, I’d take my son out with me in a stroller and that was harder than I could have imagined. I couldn’t understand how some people out there with strollers made it look so easy, just gliding along like it was nothing. I was not a glider. I was a hot mess who looked like I needed a medic.

But at least when I had the stroller, I felt like people passing by could look at me and give me that knowing nod. They understood, on at least some level, why it was hard. But when it was just me alone, I felt I had no excuse. Forget the fact that I was only 5 weeks postpartum. Or even 20 weeks postpartum. What I wanted, more than anything, was a sign on the back of my shirt explaining why I was so slow. It would explain “please excuse me, I just had a baby,” (even when he wasn’t a baby anymore.)

The same thing happened when I had my second son, but it was even harder because I was still trying to catch up from having my first son 2 years earlier. I went for a walk on the beach pushing a stroller and I was sore for days, and that was my turning point. I worked hard, harder than I think I ever have, to get myself back in shape. I worked so I wouldn’t need that sign for my back anymore.

But here’s the thing, and it’s going to sound harsh. No one cares. No one but you. This is YOUR journey, and you have to do what makes YOU happy. No one else is even paying attention. I mean, sure people care about you. They want you to be healthy. But they don’t really need to know why you’re slower this year than you were last year, or why you’re not signing up for as many races. They probably don’t even notice, to be honest. They just want to know you’re okay. They’ve got their own challenges to deal with without concerning themselves with yours.

I’m currently gearing up for my 4th ultramarathon, and getting in back to back runs is an important element to my training so I can experience running on tired legs. So I ran a 6 miler recently the day after a 19 miler and my legs felt like lead. It was great training, but I felt like that postpartum runner again. And I felt it even more so when a super fit runner came blowing past me from the opposite direction without acknowledging me in the slightest. My first thought was that he was an asshole. But then I realized that was only because I felt like the kid who never got picked to be on anyone’s team in gym class. Which, by the way, I WAS THAT KID. And then I thought “I bet HE didn’t run 19 miles yesterday!!” And then, “well, maybe he did. How do I know? And how would he? And WHY does that matter anyway?” Because it really doesn’t. He’s got his mission and I’ve got mine.

I have friends who are overweight and run marathons. I also know some people that look fit enough to fly like the wind and it takes them twice as long to run a race than it would for me. I have friends with asthma and shin spints and injuries who still run. I have friends who have babies who get right out and run without skipping a beat and others who have never had babies and are still considered slow on their best days. I have fast days and slow days and mostly days in-between. All of it is great. All of it is getting it DONE. It doesn’t matter where the finish line is. It’s that you got there, whether you ran, walked, or crawled.

I have clients with lofty aspirations. Some want to run their first marathons. Some want to run a race a month. Some want to beat a certain PR. Goals are good. They help drive us and motivate us to push harder. But we always have to be careful because they can destroy us too, if we don’t get there right away or even at all. I never want to forget it’s about the journey to get somewhere that matters more than the destination itself. There’s another cliché saying for you.

I remind my clients that you can’t compare yourself to anyone else. What makes us great is that we are all different. I could easily compare myself to my friend who runs fast in an effortless fashion, but her legs are twice as long as mine. And there are so many other factors involved too. You don’t know what that girl on the track ate for breakfast or what she did yesterday that could affect her today. You don’t know if that guy had a good day today or a bad one last week. Because we all have “those days.” You don’t know if he has more fast twitch muscles or if she has more slow twitch muscles. You don’t know their struggles, their victories, or what’s going on in their lives either. And even if you do, those things aren’t yours. You do YOU. Make your goals, but make them for YOU. Don’t hold a yardstick up to anyone else. And if you don’t quite get to where you had wanted, give yourself some grace. It’s okay to fall. It makes victory so much sweeter when you get back up.

Fat on the Inside

I remember this day clearly in my head despite the fact that it was a day B.K. (“Before Kids” which seems like forever ago in relation to most things.) I was shopping for some new clothes and I held up a pair of size 6 jeans. They looked so tiny! I thought to myself that there was no way I could fit into those, but I felt I should at least TRY to get them on to see where I was in my weight loss journey. I added them to my pile and soon headed to the dressing room. When I got to the jeans in question, I slid them on and buttoned them. They fit.

I took them off and looked at the tag on them. Both the outside tag and the inside one. Both said they were, as I thought, a size 6. But how was that possible? Was this size 6 more like a size 10 or 12 somewhere else? Were they supposed to be a baggy fit or something? No.

This. This is what happens when you lose a lot of weight. Because even when your body changes, even when the workouts get easier, even when the scale number has changed significantly, and when people tell you that you look great and to “keep it up” and everything is less of a struggle and the mirror looks different than it used to .. Even when all of those things happen .. You still don’t get it. You still don’t realize it. Your brain hasn’t caught up to your body yet. You’re still fat on the inside.

I went from a size 20 to a size 6. I didn’t even feel the numbers going down because I didn’t buy all the “in between” sizes. It was too expensive and I was too cheap. And honestly, I didn’t know if I’d be able to keep the weight off. Just as many people have “skinny jeans” they aspire to wear someday in their closets, I had “fat jeans.” A safety net. So when I finally got to a size 6, I not only didn’t think there was any possible way that I could get my big thighs or enormous butt into them, but if I did, I didn’t know how long they would last.

People treat you differently when you lose weight. You don’t even notice it so much when you’re at your heaviest, though you are painfully aware of the fact that maybe that cute guy isn’t looking at you because he’s not interested in “your type.” But in everyday life, you’re just doing just that, living. And then you lose weight and people are literally opening doors for you. And looking you in the eye when they talk to you. And sometimes those cute guys are even checking you out. Some people are nicer to you. And other people, the more insecure ones, might even be not-so-nice. You start to notice these things, but you still might not associate it with dropping some dress sizes. Because you’re still the same person, right?

Except you’re not. You’ve changed. And people’s reactions to you have changed too. But what’s even harder is what’s going on inside your head, because you’ll never be able to see what others do. It takes time for you to change what you are, but that’s what you have to do when you lose weight. Accepting it is harder than you may have realized.

I used to go home after work and eat and watch TV. I started going to the gym instead and doing some more “mindful eating” and found a different lifestyle actually made me happier than the food used to. However, it took a long time for me to accept that life was different from here on out, that this wasn’t just a “phase” I had to get through before going back to my old life. Your brain is the last thing to make peace with those changes. There are so many things associated with the comfort of food and the rituals of eating. Memories are directly connected with smells and tastes. Acceptance is part of getting healthier, and this is a life lesson, not just something you connect with in AA. Knowing that you can’t go back is both exhilarating and scary. You have to mourn that life a bit in order to move on. You have to break-up with those bad habits. In my opinion, it’s okay to come back and visit sometimes so you don’t relapse completely. Just not every night, or even most nights. But if you think you have to live on broccoli and never get ice cream again, you’re going to go a little insane eventually. Like with anything, there’s some safety in moderation. And in limits.

To be clear, I’m not telling anyone that they have to be skinny to be happy. Happiness, love, and all the beautiful things in life come in every shape and size. And I am certainly not one to talk, because I am not built like a barbie doll. I have soft curves and cellulite and stretch marks and hips and thunderous thighs. And that’s, for the record, because I love food. All the food. Food will always be my biggest weakness. I can run 20 miles tomorrow, but I can’t leave that piece of chocolate cake in the fridge uneaten. But I also know I’m not willing to stop really “living,” and food and the happiness that goes with it is a part of that. No matter your size .. a size 0 or a size 25.. it’s what we were given and it might go up and down and no matter what, we should wear it. Stretch out and prance around in it. It’s a lot to be grateful for.