Rushall notes, 2003

Training effects are still believed to be "transferable" between activities. "Cross-training", "auxiliary training", varied training stimuli, etc. are still popular topics in coaching books, at coaching clinics, etc. The myth of training transfer and generalization is strong and confused. There are three general forms of training adaptations that occur. They cause different benefits, or lack of benefits, for athletes who are exposed to "modern" coaching programs.

When repeated training stimuli are experienced by trained athletes through continuous or interval training, physiological adaptations occur in muscles. For example, in endurance training of a specific pace/intensity, a certain amount of capillarization occurs, mitochondria adapt, the heart works at a particular intensity to provide blood and fluids to the working muscles, etc. Often, a "steady state", a pattern and mix of physiological responses, occurs to accommodate the training activity. Since living organisms learn to function in particular ways to particular situations, training at a particular rate or intensity will produce specific adaptations that will not be activated for different rates or intensities. In research when one limb is trained and associated with altered physiological factors, exercise with the untrained limb does not use the trained adaptations of the trained limb. The "good" physiological changes are only specific to the movement that produced them. The higher the level of training and performance accomplishment in the athlete, the more specific are the physiological adaptations.

• When an individual is markedly untrained, any training will have an effect on any activity up to a certain point. This is why general fitness programs improve physical function in low-performing persons. However, there comes a stage in fitness development when basic function is no longer enhanced and specific function starts to be differentiated if sufficient volume and repetition of physiological demand is experienced.
• It is unsound to apply training principles appropriate for untrained individuals to talented athletes who have a good level of fitness for a host of varied activities. This is the main error made by coaches who foster and advocate varied and general activities as being beneficial for performance improvement in serious athletes. The Coaching Science Abstracts' issues covering the Principle of Training Specificity contain the research articles that support this assertion.

The belief that "general" and "cross-training" exercises are valuable for specific competitive performances is erroneous. If an athlete is going to perform in a certain manner in a competition, then training exercise intensity, duration, and form need to mimic the intended competitive demands. Otherwise, trained fitness will not be employed in the sport competition. For example, swimming coaches set a substantial amount of training at 75%, 85%, and 95% of intended race pace/intensities. "Percentage" training of that type is useless for competitions that are to be performed at a particular "100% pace/intensity" because for each varied exercise intensity, the physiological demands are specific and differentiated and inappropriate for a race.

In "top-level" performers, a common reason for performance declines in specific events is because a large amount of "physiological" training has not occurred at the level required to achieve intended performance goals. Specific physiological adaptations occur at the peripheral muscular/cellular sites. Thus, when a competitive performance intensity requires a specific mix of physiological functions that have had little stimulation and adaptation through training, the body reacts in a relatively "untrained" manner. This results in disappointing performance levels and deterioration in movement economy.

There are activities that improve mainly through neural reorganization rather than physiological adaptations. The most common and researched activity that has shown this effect is strength training. With strength training, the first stage of adaptation is a neural reorganization of existing physical resources, which results in strength improvements in the trained activity. For example, when an untrained individual practices bench presses, bench-press strength improves without any major change in muscle state (e.g., hypertrophy). This "reorganization" is represented in the brain as a movement pattern or map.

A typical research paradigm with strength training is to train one limb, while the other limb remains restricted in its movements. Usually, the trained limb improves in strength in the activity that is practiced. When the inactive limb is tested after the trained limb has improved, its strength has improved without practice! The level of improvement is less than that of the trained limb but improvement is demonstrated. This is a result of a movement map having been formed in the cerebral cortex which makes it accessible to other uses within the body. Although the map is available to the untrained limb, it is not completely transferable to that limb and so only partial benefits of strength improvements are transferred. However, this is a particular case concerning body limbs within an individual performing a mirrored movement. When movements are not mirrored, such as a seated leg press and squat, in trained athletes there is insignificant carry-over from one activity's changes to the other.

When isolated movement patterns are differentiated more specifically, such as with power training when the coordination of physical resources is very time specific, transfer to other-side unused or untrained activities is less than with basic, relatively slow strength activities on weight machines. This is why a javelin thrower can throw well with one arm but not with the other. It is also why traditional strength training improvements accomplished in a gymnasium do not transfer to applied power activities such as shot putting, discuss throwing, and javelin throwing. It is also why traditional strength trained gymnasium activities do not carry over to improvements in functional activities such as running speed, vertical jumping, and free-weight lifts. It accounts for the lack of benefit derived from strength training in collegiate and professional football and other sport performances despite annual concentrated strength training programs.

As with physiological transfer, any strength or isolated effort activities will improve similar capacity improvements in untrained individuals. This also occurs up to a certain basic level whereupon discrimination between actions begins to take precedence over generalized improvements. Thus, fitness strength programs benefit untrained individuals initially and up to a certain level but such programs do not benefit well-trained athletes.

When neural patterns are established for particular movements in one limb, there is some possibility of some transfer of mirrored movements in the other untrained limb. Apart from that, transfer is non-existent but for reasons that are different to peripheral physiological adaptations.

Sporting tactics or strategies involve the symbolic representation of sequences of existing bodily movements and resource uses. Tactics and strategies are represented only in the cerebral cortex at the symbolic level and have the greatest potential for transfer to competitive settings. Despite that potential, transfer is still limited. That limitation is recognized in the advocacy of simulation training as being of greater transfer value to competitions than isolated or practice activity training.

However, strategies and plans formed and practiced at training sessions usually derive the greatest level of learning when they are practiced in blocks of repetitions. Their predictability allows feedback from one trial to be used to refine the next repetition. While predictability in training leads to improved training performances, rarely is a similar degree of predictability available in a competitive setting. Usually, a particular tactical element is appropriate when preceded by a restricted variety of stimuli (situational circumstances). Thus, some transfer of trained strategy elements can be expected in competitions but the execution of the intended strategies will only be predictable when game situations are experienced in sufficient volume that the recognition of all appropriate eliciting stimuli occurs. That is only achieved when game or competitive experiences occur in sufficient volume to produce the added specific recognition and implementation stimuli.

One should not expect strategies or tactics to be implemented very well without actual game or competitive repetitions. A sporting myth that is commonly propagated is that a week's practice is devoted to particular changes in strategies or tactics to be implemented in the next competitive setting. While some changes might be witnessed, the precision of such changes usually are relatively ineffective and imprecise. That leads to the assertion that team or strategic game performances rarely improve when tactics are frequently changed from opponent to opponent despite practice simulation-training. Practice content that continually changes does not allow the development of the precisioned or automatic implementation of strategies or tactics without repetitious implementation in game or competitive settings. This produces a dilemma for coaching programs, how much can tactics be varied and changed in a season of competitions and how limited should those changes be?

The transfer of training effects at the physiological, neural, and symbolic levels differ. The greater the similarity of stimulation experienced at practice is to competitive settings, the greater will be the transfer of benefits derived from training and practice. This is a fundamental principle that is supported by the Principle of Training Specificity and cannot be ignored when exercising serious athletes. It can be ignored in untrained individuals but only up to a certain level of physical function and fitness. The importance of using competitive situations as training extensions, rather than always very important competitions cannot be overlooked. However, there are many sporting competitions that are all of equal importance. In those situations, performance improvements across the period of competitions should rarely be expected. At the same time performance inconsistencies should expected because of the lack of correlation between training/practice demands and the requirements of competitive tasks.

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