Respuesta :
The principle of training would you apply if you wish to improve your backstroke in swimming is - specificity.
Specificity
According to this principle of training that tells that the response of the body is specific to the particular physical activity. Using this training principle helps in achieving desired goals by having a focused, efficient, effective technique.
The technique of the backstroke in swimming is a specific activity that allows it to improve it.
Learn more about the principle of training:
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