Lee emphasized what he called "the style of no style". This consisted of getting rid of the formalized approach which Lee claimed was indicative of traditional styles. Lee felt the system he now called Jun Fan Gung Fu was even too restrictive, and eventually evolved into a philosophy and martial art he would come to call Jeet Kune Do or the Way of the Intercepting Fist. It is a term he would later regret because Jeet Kune Do implied specific parameters that styles connote whereas the idea of his martial art was to exist outside of parameters and limitations.

After his match with Wong Jack Man in 1965, Bruce Lee changed his approach toward martial arts training. Lee felt that many martial artists of his day did not spend enough time on physical conditioning. Bruce included all elements of total fitness— muscular strength, muscular endurance, cardiovascular endurance, and flexibility. He utilized traditional bodybuilding and weight training techniques to develop muscular strength. Lee was careful to emphasize that mental and spiritual preparation were fundamental to the success of physical training in martial arts skills. In his book The Tao of Jeet Kune Do, he wrote Training is one of the most neglected phases of athletics. Too much time is given to the development of skill and too little to the development of the individual for participation." "JKD, ultimately is not a matter of petty techniques but of highly developed spirituality and physique.

The weight training program that Lee developed during a stay in Hong Kong in 1965 placed heavy emphasis on arm development. At that time he could perform single bicep curls with 70 to 80 lbs (about 32 to 36 kg) dumbbell for three sets of eight repetitions. Other weight training exercises, such as squats, push-ups, reverse curls, concentration curls, French presses, and both wrist curls and reverse wrist curls. he performed consisted of 6 to 12 reps (at the time) per set. While this method of training targeted his fast twitch muscles, it also resulted in gaining muscle mass, placing Bruce a little over 160 lbs (about 72 kg).

Lee was documented as having well over 2,500 books in his own personal library, and eventually concluded that "A stronger muscle, is a bigger muscle", a conclusion he later disputed. Bruce forever experimented with his training routines to maximize his physical abilities, and push the human body to its limits. He employed many different routines and exercises including skipping rope, which served his training and bodybuilding purposes effectively.

Lee believed that the abdominal muscles were one of the most important muscle groups for a martial artist, since virtually every movement requires some degree of abdominal muscle activation. He trained daily from 7 a.m. to 9 a.m., exercising stomach muscles, stretching to increase flexibility, and running to increase endurance. From 11 a.m. to 12 p.m. he would weight train and cycle. A typical aerobic conditioning routine for Lee would be to run a distance of two to six miles in 15 to 45 minutes, in which he would vary speed in 35 minute intervals. Additionally, Lee would also ride the equivalent of 10 miles (about 16 kilometres) in 45 minutes on a stationary bike.

Lee would sometimes exercise with the jump rope and put in 800 jumps after cycling. He would also include conditioning techniques to toughen the skin on his fists, including thrusting his hands into buckets of harsh rocks and gravel. He would do over 500 repetitions of this on a given day.

Chuck Norris states, "Lee, pound for pound, might well have been one of the strongest men in the world, and certainly one of the quickest."

Jeet Kune Do "Way of the Intercepting Fist," is a hybrid fighting system and life philosophy founded by Bruce Lee in 1967 with direct, non classical, and straightforward movements. Jeet Kune Do is primarily an open hand system. The system works on the use of different 'tools' for different situations. These situations are broken down into ranges (Kicking, Punching, Trapping, & Grappling), with techniques flowing smoothly between them. Also, it is referred to as a "style without style". Unlike more traditional martial arts, Jeet Kune Do is not fixed or patterned, and is a philosophy with guiding thoughts.