This could also be called the snowflake principle, since it highlights that no two climbers—or their optimal conditioning program—are the same. The best training program for you will target your specific weaknesses, address past or present injuries, provide sufficient time for recovery, and be structured to provide the greatest output for the available training input.
Since there is no other climber quite like you, there is no other climber's conditioning program that you'd want to copy—doing so will provide less-than-optimal results and might even get you injured.
The principle of specificity may be the most important of all for climbers to heed. It simply states that the more specific a training activity is to a given sport—muscle group, work load, velocity and pattern of movement, body posture, and range of motion—the more it will contribute to increasing performance in that sport. Therefore, for an exercise to produce meaningful gains in functional strength and endurance for climbing it must be markedly similar to climbing. Obviously, exercises that involve actual climbing motions (bouldering, fingerboard pull-ups, H.I.T. Workout, and such) are the most specific and will have the greatest transfer to climbing performance.
Effective training must also target the specific muscle fiber type and energy system most used in your preferred style of climbing. For instance, hard bouldering draws largely on fast-twitch muscle fibers and the ATP-CP energy pathway, so your want to favor brief, high-intensity exercises that target these constraints. Longer traditional or sport climbs, however, typically demand extended and alternating use of fast- and slow-twitch muscle fibers with energy coming predominantly from glycogen stored in the muscles and liver. To specifically train these systems, you'd want to perform many high-repetition exercises or climb for mileage at the gym or crag.
This grand daddy of training principles states that in order to increase functional capacity for exercise, it is necessary to expose the neuromuscular and cardiovascular systems to a level of stress beyond that which it is accustomed. You can achieve this overload by increasing the resistance and intensity, volume, and speed of training, or by decreasing the rest interval between successive sets.
The best method of creating overload depends on the desired outcome of a conditioning program. For example, to excel in bouldering you'd want to create overload by increasing resistance and exercise intensity in order to build maximum strength and power. A roped climber would be more interested in developing local endurance and, thus, he should create overload by increasing both the exercise volume and reducing rest intervals between exercise sets. Finally, a big wall or alpine climber in need of greater stamina should train at a lower overall intensity and create overload by increasing total daily exercise volume."