No two athletes are alike.
You all carry varied and intrinsic physical and mental characteristics. You all have your own unique strengths and weaknesses.
Because of these individual differences, you will respond to a training stimulus differently than your friend, training partner or teammate.
The bottom line is that certain training methods may elicit increased performance outcomes in some athletes but decrease the same in others. Basically, you may find doing high intensity intervals (HIIT) jacks up your endurance capacity, whereas your buddy may actually lose some endurance capacity unless he does longer duration cardio work at a lower intensity.
(Aside: HIIT is not the holy grail of energy systems training for everyone. Nor is long slow cardio. I still strongly believe that theses different forms of energy systems training each have their place in a well designed training program.)
Instead of blindly copying the latest training program of XYZ famous pro athlete, found on the glossy pages of the most popular fitness magazines, don’t you think it’s wiser to understand the guiding principles that form that program and apply those in a unique and creative manner instead?
By doing so, your specific needs as an individual and as an athlete will be met; strengths will be bolstered and weaknesses will be buffered.
By individualizing your training regimen, you or your athletes can invoke optimal training responses in order to achieve maximal performance outcomes.
And isn’t that what the training program is all about?