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.