El Segundo“Jason Kahn provides amazing personal training in El Segundo California that is specific to each of his clients’ needs. His first priority is always his clients, especially their safety. Jason Kahn has helped me train specifically for volleyball, and he creates plans that help me improve my overall athleticism as well as direct applications to my sport. I would recommend his training to anyone with any ability level. He will definitely make a difference in your fitness.”  —- Stephen Moye, Stanford Volleyball athlete

JK Physical Culture“Jason helped me immensely early in my career teaching me the foundations of strength and conditioning and how to properly perform certain lifts to give me the best results while keeping me free from injury.  Jason helped me increase my strength, power and mobility… all of which are very important to me as a baseball athlete.  If you’re looking to improve your sport or just look better and get stronger go see Jason at JK Physical Culture .. …you won’t regret it!”— Andrew Keefer, TCU Baseball athlete

El Segundo

“I’ll try to keep this short.

If you’re looking for someone in the El Segundo and surrounding areas who has not only spent years upon years (like 20+) perfecting his craft in health and fitness, but CONTINUES to do so daily — Jason is for you.

From strength, fat loss, lean mass gain, flexibility, mobility and overall health and nutrition, this is your guy. Extremely knowledgable, easy to work with and won’t be afraid to say, “no, I don’t agree with that and here is why. This is why I believe it doing it this way. Here is the research and science behind it” He’s a man of strong convictions. Convictions there to help others around him. All while ready to take advice and insight from others around him.

Overall, just a good dude with a solid sense of humor who’s really fun to be around.

Ps – When you guess his age…you’ll probably get it wrong. Just sayin’. ;o)”—-Joe Buys-Dream Impossible


“Jason has helped me enormously in meeting my goals as a competitive cyclocross racer.  He created a strength training program specifically designed to the demands of my specific cycling discipline.  He worked with my time constraints and specific needs to develop a program that would work best for me. Thanks again Jason!!!”—-Norm Laird

Below is a study documenting the results that supervised training delivers when it comes to strength:

 2000 Jun;32(6):1175-84.

The influence of direct supervision of resistance training on strength performance.



The purpose of this study was to compare changes in maximal strength, power, and muscular endurance after 12 wk of periodized heavy-resistance training directly supervised by a personal trainer (SUP) versus unsupervised training (UNSUP).


Twenty moderately trained men aged 24.6 +/- 1.0 yr (mean +/- SE) were randomly assigned to either the SUP group (N = 10) or the UNSUP group (N = 8). Both groups performed identical linear periodized resistance training programs consisting of preparatory (10-12 repetitions maximum (RM)), hypertrophy (8 to 10-RM), strength (5 to 8-RM), and peaking phases (3 to 6-RM) using free-weight and variable-resistance machine exercises. Subjects were tested for maximal squat and bench press strength (1-RM), squat jump power output, bench press muscular endurance, and body composition at week 0 and after 12 wk of training.


Mean training loads (kg per set) per week were significantly (P < 0.05) greater in the SUP group than the UNSUP group at weeks 7 through 11 for the squat, and weeks 3 and 7 through 12 for the bench press exercises. The rates of increase (slope) of squat and bench press kg per set were significantly greater in the SUP group. Maximal squat and bench press strength were significantly greater at week 12 in the SUP group. Squat and bench press 1-RM, and mean and peak power output increased significantly after training in both groups. Relative local muscular endurance (80% of 1-RM) was not compromised in either group despite significantly greater loads utilized in bench press muscular endurance testing after training. Body mass, fat mass, and fat-free mass increased significantly after training in the SUP group.


Directly supervised, heavy-resistance training in moderately trained men resulted in a greater rate of training load increase and magnitude which resulted in greater maximal strength gains compared with unsupervised training.

[Indexed for MEDLINE]