Private Strength Training • Naperville, IL

Train for the life
you want to live.

Science-backed, one-on-one strength training in just two 20-minute sessions per week. Private. Appointment-only. Built for the demands of your life.

Book Free Consultation What to Expect Watch Our Video
20
Minutes Per Session
2x
Per Week
1:1
Personal Training
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Why Invested Strength

Strength training
done differently.

Most people spend more time in the gym than they need to and still don't get the results they want. We built a better system. Twice a week, 20 minutes, with your trainer beside you the entire time. Nothing wasted.

01

Science-Backed Protocol

High-Intensity Training on MedX equipment drives real adaptation through controlled tempo, time under load, and true muscular fatigue every session.

02

Private Studio Environment

Appointment-only. No crowded gym floors, no waiting for equipment. Your trainer is with you the entire session, cueing your form, adjusting your effort, and coaching you through every rep from start to finish.

03

Safe for Every Body

Designed for adults who want to get stronger without getting hurt. Our method is gentle on joints while producing measurable, lasting results.

20
Min sessions
Strength training at Invested Strength Studio Private training session
Your First Visit

We hope
you fail.

That's where real strength begins.

When we say "failure," we're not talking about doing something wrong. We're talking about reaching the point where your muscles are fully and safely challenged. That's where real progress happens.

Your complimentary one-hour consultation is designed to help you fully understand how this works and what it actually feels like, without pressure or guesswork.

Our training is efficient, controlled, and low-sweat. Most clients are surprised by how effective it is in such a short amount of time. You won't be rushed, and you won't be sold. You'll leave with a clear understanding of how your body responds, what real effort feels like, and whether this is the right fit for you.

Book Your Free Consultation
Your consultation includes
01
A warm welcome and goal conversation

We start by getting to know you. Your history, your goals, any injuries or concerns. No forms to fill out in a waiting room.

02
InBody body composition scan

A precise, painless scan that measures muscle, body fat, and metabolism. Your trainer walks you through the results clearly so you understand exactly where you are starting.

03
Introduction to the method

We explain why our approach is different, what time under load means, and why reaching momentary failure is the goal not something to avoid.

04
Guided trial on the machines

You try several machines with your personalized settings recorded. You experience what the training actually feels like in a safe, guided environment.

05
A straightforward review of your options

At the end we walk through membership and scheduling options clearly. No pressure. Just the information you need to decide if this is right for you.

If you've never experienced this kind of training before, this is the best place to start.
Hear It From Us

The story behind
Invested Strength.

Meet Megan, hear from real clients, and get a clear picture of what to expect from your InBody scan to the slow, controlled movements that make this method so effective. Two minutes that answers most of the questions people come in with.

The Process

What to expect
from day one.

We take the guesswork out of getting stronger. From your very first visit, everything is designed to feel simple, supported, and effective.

01

Free Consultation

A complimentary first visit with no pressure and no commitment. You'll tour the studio, meet our training team, and try the equipment to find your starting point.

02

No Long-Term Contract

Before your first paid session you'll review a simple service agreement outlining your plan and billing terms. It is clear, fair, and there to protect both you and us. Your first consultation is completely free with no obligation to continue.

03

Your First Session

A personalized total-body circuit on our full equipment floor. Your trainer is with you at every machine, establishing your settings, cueing your form, and coaching you through each exercise at the intensity level you want to bring that day.

04

Ongoing Progress

Typically twice a week, 20 minutes. Every session is logged. Weights are increased as you get stronger. Your trainer tracks your progress over time and uses that data to keep you moving forward safely and consistently toward your goals.

Who We Serve

Built for people who take
their health seriously.

For Professionals
Busy professionals
For Professionals
No time to waste. Maximum results.
Two 20-minute sessions per week fit into even the most demanding schedule without sacrificing effectiveness.
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For Women 40+
Women 40+
For Women 40+
Strength that changes everything.
Build lean muscle, protect bone density, and reclaim the energy and confidence that strength training uniquely delivers.
Learn More
For Active Adults
Active adults
For Active Adults
Safe, effective, and joint-friendly.
Our method is gentle on joints and works with your body. Clients in their 60s and 70s see remarkable results.
Learn More
For GLP-1 Users
Megan Costilow transformation
For GLP-1 Users
Protect your muscle. Maximize your results.
GLP-1 medications cause significant muscle loss alongside fat loss. Strength training is the essential counterpart that protects your body and makes your results last.
Learn More
Our Story

Not a gym.
A studio.

Invested Strength Studio was built on a simple belief: strength training should be accessible, safe, and effective for every adult. Not just athletes. Not just the young. Everyone. We use MedX and Nautilus equipment alongside a proprietary method built on time under load, controlled movement, and reaching true muscular fatigue. Every session is tracked. Every detail is intentional.

Private, appointment-only studio
MedX & Nautilus equipment
Science-based HIT method
InBody body composition tracking
Naperville, Illinois
Meet the Team

The people
behind your results.

Megan Costilow, Co-Owner and Trainer
Megan Costilow
Co-Owner & Trainer

Now in my fifties, I'm stronger and healthier than I've ever been. After losing more than 110 pounds, I turned my personal transformation into a passion for helping others achieve their own strength and confidence. As a trainer, manager, and now owner, I understand both the challenges and the rewards of this journey. My mission is to ensure every client feels supported, capable, and proud of their progress, no matter their starting point.

Josh Costilow, Co-Owner
Josh Costilow
Co-Owner

My own results from training have been incredible. I feel stronger, sleep better, and have more energy than ever before. As Megan's husband and co-owner of Invested Strength, I may not be training clients directly, but you'll often see me around the studio. I'm proud to support our team and to share how strength training has improved my own life, giving me more time and vitality with my kids and grandkids.

Lucas, Trainer
Lucas
Trainer

I used to think I truly needed 4+ hours a week in the gym, and that if I didn't commit enough time the results wouldn't match. That changed after learning and using the training style we implement at Invested Strength. I am still able to push myself to the same limits as before, without the risk of overtraining, injury, or wasting unnecessary time. My current goal is to push my physique as far as I can, to be a testament to the results you can achieve here.

Tim Ryan, Advisor
Tim Ryan
Advisor

With over 40 years of experience in strength training, coaching, and studying the science behind what we do, Tim's expertise has elevated the training ability of Invested Strength staff. Tim has been featured on strength forum panels and High Intensity University podcasts, and has made unique modifications to some of the machines at the studio, further enhancing the ability to safely and effectively train your hardest.

Lance Rubin, Advisor
Lance Rubin
Advisor

Lance brings more than 40 years of experience in the fitness world and a lifelong passion for strength and performance. Alongside his career as an equine dentist, he has spent decades studying and applying the principles of High Intensity Resistance Training. Training just 1 to 2 times per week, Lance continues to demonstrate outstanding strength and vitality well into his 70s, a living example of what consistent, intelligent training can do for long-term health and quality of life.

The Equipment

Meet our other
team members.

Invested Strength Studio training floor
MedX strength training equipment
MedX
Medical Grade Equipment

Our MedX and Nautilus machines are built to work with your body, not against it.

Smooth, Controlled Resistance

Every machine delivers resistance that keeps your movements safe while helping you get stronger and improve flexibility. No jerking, no momentum just clean, effective work.

Designed to Protect Your Spine and Joints

MedX machines go a step further with advanced engineering focused on spinal and joint safety. Originally developed in partnership with the University of Florida for medical rehabilitation, they allow you to train hard without the risk traditional free weights carry.

Effective at Any Level

Whether you are a complete beginner or a seasoned athlete, our equipment meets you where you are. Every rep is working for you precisely, safely, and progressively.

Common Questions

Everything you want
to know.

Sessions are 20 minutes. Most clients train twice a week, which is the sweet spot for producing real strength gains while allowing full recovery between sessions. That said, we work with your schedule and some clients train once or three times per week depending on their goals and availability.
None at all. Most of our clients have never done structured strength training before or haven't in years. Your trainer walks you through everything from day one. No experience required, no judgment, ever.
Our method was specifically designed with joint safety in mind. The slow, controlled movements used on MedX equipment minimize stress on joints while maximizing muscle engagement. Many clients train around existing injuries with great success. We always encourage you to share any health concerns with your trainer before your first session, and we recommend discussing major conditions with your doctor.
Almost entirely. Invested Strength is a private, appointment-only studio. You're never waiting for equipment, and your trainer is with you for every single rep of the full session, actively cueing your form, coaching your effort, and helping you get the most out of every exercise at the intensity level that is right for you that day. It's a quiet, controlled environment designed for people who are serious about results but have no interest in the typical gym experience.
Most clients notice meaningful improvements in strength within the first four to six weeks. Because every session is tracked and weights are progressively adjusted, you'll be able to see your progress clearly over time. We also use InBody body composition scans to measure real changes in muscle and body fat.
No long-term contracts. Before your first paid session you'll sign a straightforward pricing and service agreement that outlines your plan, billing terms, and session policies. It's clear, simple, and there to protect both you and us. Your first consultation is completely free with zero obligation.
Whatever you're comfortable moving in. We've had clients train in workout clothes, work clothes, and yes, even a Halloween costume and a suit. The only recommendation is a clean pair of shoes, or you're welcome to work out in your socks. Sessions are only 20 minutes, so there's rarely a reason to change.
It's a relaxed, no-pressure introduction to the studio. You'll tour the space, meet our training team, talk through your goals and any health history, and try the equipment so we can find your starting point. The whole thing takes about an hour. There is absolutely no obligation to continue.
You are a client of Invested Strength Studio. You are always welcome to schedule with the same trainer and we will do our best to accommodate that preference. If a change ever becomes necessary, we will notify you in advance and give you the opportunity to reschedule.
You are welcome to schedule with any available trainer at the studio. Each trainer uses the same method and tracks your settings and progress, so your experience stays consistent no matter who leads your session.
Client Results

What our clients say.

"

The proof is in the paddling! I was able to kayak 4 miles on the Colorado River on my own after working with Lucas and Megan consistently over the last few months. I had only been in a kayak once before. What an incredible feeling to have the strength to make the most of that trip.

Tracey M.
"

Invested Strength Studio has been a complete game changer for me. I was always a bit nervous about committing to a workout routine, but there is something truly special about ISS and their amazing team. I now look forward to every single appointment. I feel better, healthier, and overall happier.

Kerry K.
"

I have been strength training with Megan for over a year and could not be happier that she opened her own studio. She is passionate, always furthering her knowledge, and so encouraging. The studio is very welcoming. I have become more fit and stronger, and my workouts have been a wise investment in my overall health.

Wendy T.
"

So happy I started going to Invested Strength! I have felt so much better and stronger after 3 months. It is something I have been able to stick with and see results from. Highly recommend!

Tricia V.
"

I was present for opening day. I believe in Megan and the method of investing in my raw potential to seek positive results. I recommend everyone try and live a healthier and happier life.

Stephen M.
STRONGER
292 Rickert Drive, Suite 148 • Naperville, IL • 630-344-9368

Your first visit
is on us.

Come see the studio, meet your trainer, and experience the method firsthand. No commitment. No pressure. Just 20 minutes that might change how you think about getting stronger.

Book My Free Consultation

Call or text: 630-344-9368

20
Minute Sessions
2x
Per Week Typical
1:1
Personal Training
$0
First Visit
Book Free Consultation Call/Text