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I understand that there are 4 that i know of which are:

F- Frequency (How long you train for)
I - Intensity (How hard you train)
T - Time (How long you train for)
T - Type (What kind of training you are doing)

I have only ever come across these...

Oh and also...

S- Specificity (Making the sport training "tailor made" for the person's individual needs)

P- Progression (Making the training increase in intensity naturally, thus gradually improving the person's fitness, rather than all at once)

O - Overload (Preventing the training from injuring the person by adhering to the F.I.T.T, as seen above, rules)

R - Reversibility (Making sure the person who is doing the training doesn't get injured and then doesn't do any training whilst hurt, which will then decrease their fitness, skill and stamina)

Hope this helps.

Source(s):
GCSE P.E Student