Bruce Lee cared deeply about his physical fitness and tracked the evolution of his training in personal notes and diary, which have been recollected and published in The Bruce Lee Library by John Little, a "martial arts historian" from The Bruce Lee Estate. Lee typically exhibited a very lean and muscular appearance in his films, particularly in his upper body. Bruce Lee felt many martial artists of his day lacked the necessary physical fitness to back up their skill. In his book 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."
Bruce Lee used every known technique and resource in aiding his physical fitness, including the use of electric current as an aid to strength training. However, his muscle stimulator was only one of many pieces of equipment and exercise routines Lee used to achieve his on-screen physical appearance.
The weight training program Lee used during a stay in Hong Kong in 1965, indicated bicep curls of 80 pounds and 8 repetitions[5] for endurance. This translates to an estimated one-repetition-maximum of 110 pounds[6], placing Lee in approximately the 100th percentile for the 121 to 140 pound weight class[7].
Bruce Lee was light because he was more interested in lean muscles and not bulky mass. His exercise routines consisted of polymetrics and cardiovascular training. Bruce did not resort to traditional "body building" techniques to build mass, he was more interested in muscle strength and contraction. Hence, he did low reps, high weight and developed strategies to increase muscle tension and resistance.
Of all the muscles Bruce Lee developed, his abdominal muscles were among the strongest: rock solid, deeply cut, and highly defined. Lee believed the abdominals muscles were one of the most important muscle groups for a martial artist since virtually every movement requires some degree of abdominal work. Perhaps more importantly, the "abs" are like a shell, protecting your ribs and vital organs.
Bruce Lee's washboard abs did not come from mere abdominal training; he was also a proponent of cardiovascular conditioning and would regularly run, jump rope and ride a stationary bicycle. A typical excercise Lee would perform would be to run covered a distance of two to six miles in 15 to 45 minutes.