Mark Leffler - Certified personal trainer located in San Francisco, California.

My name is Mark Leffler and I’m an ACSM Certified Personal Trainer in San Francisco, CA.

I began my career in the fitness industry in the Greater Boston area of Massachusetts in 2009. Since then I have relocated to the west coast, have met some great minds in the industry, and have had the opportunity to work with many people of diverse backgrounds. Learn more

Principles I train by



WTFO believes in shared knowledge and educates clients, during their training, on the scientific disciplines behind an excellent foundation for your best fitness and wellness.



WTFO believes in keeping you healthy. You are encouraged to perform exercises that are beneficial to your health, but challenge your will.


Form and Function

WTFO believes maximum benefits, in strength and mobility, are achieved by aligning your training routine with physical demands encountered on a daily basis.

WTFO reviews

5 star overall rating 14 reviews
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Mike K. yelp profile picture

Mike K. says,

5 star rating 08/10/2014

I've been working out with Mark for over a year and a half now, and am really glad I found him. Prior to starting to work with Mark, my workouts were...

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Kaitlyn T. yelp profile picture

Kaitlyn T. says,

5 star rating 03/11/2014

I've watched my body change shape over the past 16 months of working with Mark. And at first I didn't expect it... For most of my life, I thought that a...

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Rachel N. yelp profile picture

Rachel N. says,

5 star rating 17/05/2011

Posting this for a friend who's a non-Yelper: Mark is an exceptional trainer. Both my brother and I went to Mark two months ago explaining that while we...

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