As she is training for the upcoming New York marathon, Barbara started running 4 miles daily and after 6 months, she is running 25 miles daily. This is an example of which of the following principles
A. Progression B. Specificity C. Individuality D. Recuperation

The correct answer is- progression

Explanation:

The six fundamental principles in the training are the principle of- individual difference, overload, progression, use/disuse, adaptation, specificity.

The principle of progression tells us that to improve performance and fitness there should be a systematic and gradual increase in the intensity with respect to time. This helps in increasing the performance of any athlete without the chances of injury.

So here Barbara has increased running distance up to 25 miles after 6 months of starting training which shows she is following progression principle.