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J King Performance

Top Pro

Training location

Online now


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If you hire this pro, you’re covered by a money-back guarantee. Learn more

About
I’m Jack - Champion Muay Thai fighter, coach and personal trainer based in Pacific Heights San Francisco. As a 12-0 6x National Champion with substantial time spent in Thailand, I’ve been through it all when it comes to weightloss, strength & conditioning, fight skill and mental fortification. At 6’5” and 225 lbs, I’ve been the skinny guy in the room, the overweight guy, and someone who lacked confidence. I know what it’s like to start from scratch—which is why I compassionately coach real people with real lives, working together to ensure championship level success at a pace that makes sense for each individual. I offer everything I’ve learned over the past 20 years to high achievers in San Francisco tailored to their individual goals including: 🌴Weight loss & Body Transformation 🌴Strength & Muscle Building 🌴Muay Thai for Self Defense & Confidence 🌴Muay Thai for Competition (J King Performance Fight Team: 4-0) 🌴Stress reduction & Mental Resilience 🌴Mobility, Recovery & Performance I offer: • Private 1-on-1 coaching • Small group training • Corporate wellness & team-building Muay Thai workshops • School Muay Thai camps • Annual Muay Thai retreats in beautiful Sonoma County for long-term clients My coaching isn’t about quick fixes or punishment. It’s about building a body you’re proud of, developing confidence that carries into everyday life, and creating habits that actually stick. Whether you’re walking into a gym for the first time or looking to sharpen your skills, I’ll meet you where you are and help you become the strongest version of yourself. Client Results ⭐ Helped an executive lose over 60 lbs while dramatically improving confidence, energy, and health markers. ⭐ Coached teenagers from being bullied and lacking confidence to competing, sparring, and becoming leaders in the gym. ⭐ Helped busy professionals finally build a sustainable fitness routine that fits demanding careers. ⭐ Guided students of all ages to improve discipline, fitness, self-confidence, and overall quality of life. If you’re ready to build confidence, get in the best shape of your life, and learn skills that last forever, send me a message. 📩 Book your half-price introductory session today
Overview

Current Top Pro

Hired 35 times

Serves San Francisco, CA

Background checked

1 employee

11 years in business

Business hours

Sun9:00 am - 3:00 pmMon9:00 am - 8:00 pm

Payment methods

This pro accepts payments via Apple Pay, Cash, PayPal, Venmo, and Zelle.

Social media

Instagram

Services offered
Event to prep for
Fitness goals

Lose weight

Get toned

Build muscle

Gain flexibility

Client age

23 - 30 years old

31 - 40 years old

41 - 50 years old

51 - 60 years old

Projects and media
Projects and media
Reviews

Customers rated this pro highly for work quality, professionalism, and value.

Exceptional 5.0

57 reviews

5

100%

4

0%

3

0%

2

0%

1

0%

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Read reviews that mention:


pro avatar
Kaushik M.

2 weeks ago

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Hired on Thumbtack

Jack is the perfect trainer for any busy professional, and he genuinely cares. I've been training with him and I'm already down almost 20 lbs, averaging around 1.5 lbs a week WHILE getting stronger! He made it possible to be a busy startup founder and still stay on top of my health. I send him my weight every morning, and he adjusts my calorie targets based on the trend and keeps me accountable, even while I'm traveling, working late or short on sleep. Even with a restrictive vegetarian diet, he always had practical food alternatives that kept me on track without feeling miserable. On top of weight training, we added Muay Thai. I wasn't sure about it at first, but it's been a great way to learn a new skill from an experienced fighter and keep my heart rate up, and now it's one of my favorite parts of the week. He's flexible with scheduling and adapts the program to what I need. If you want real results and a coach who's truly in your corner, I can't recommend Jack enough.
Personal Training
pro avatar
Sopiko K.

Jul 2, 2026

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Hired on Thumbtack

Jack is an absolutely incredible personal trainer! My friend and I came to him starting from absolutely zero as far as our gym knowledge/experience went, and Jack built us up from the ground up, taught us everything we needed to know from the basics to the intricacies of: lifting weights, proper form, how to listen to our bodies, when/how often/how much to increase, which exercises to do to reach our goals and how to properly do them all. Most importantly, he helped us build our confidence around exercising/going to the gym as a whole. We couldn't be happier with the services he provided, his professionalism/expertise throughout the whole experience, his overall knowledge/experience and the results we achieved under his guidance. We are definitely looking forward to working with him again in the future.
Personal Training
pro avatar
Ilian H.

Jun 8, 2026

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Hired on Thumbtack

Embodies an amazing work ethic, is super professional, always responsive always on time. Jack's an amazing sensei and also an incredible human. Genuinely cares about my personal well-being & growth, consistently challenges me to improve, and personally created a fighting regiment tailored to my specific fighting style.

He's been coaching me for more than a year and I'm looking forward to our lessons for many years to come.
Private Self Defense Lessons
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Saul C.

Jun 6, 2026

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Hired on Thumbtack

Jack is a great trainer, he has been doing strength and Muay Thai training and has been very patient and knowledgable. He has helped me gain confidence to be able to go to the gym. I cannot recommend him enough!
Private Self Defense Lessons
pro avatar
Alexas W.

Jun 5, 2026

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Hired on Thumbtack

Personal Training
Credentials
Background Check

Jack Kerr