A theory is any proposed idea or explanation of a cause and effect relationship. A theory has not been proven to be true. Facts have been proven to be true or at least agreed to be true by proponderance of evidence. But a theory can be based on any number of facts and attempt to show a relationship between those facts and some end product or outcome. Proving a theory can be extremely difficult. It requires showing that all parts are true with a clear method to show the parts to be true and the manner in which this is done needs to be reproduceable (Meaning that if you got something to work, I can also do the same thing and it will work for me as well).
Many times people feel they have a theory about how something works, but is more of a belief. That is, they believe that doing X will result in Y happening.
In fitness it is even more difficult to rely on theory as each individual will react differently to the same stimulus. This is partially why it is recommended to begin a program (as a new exerciser or when changing exercises) at a relatively easy intensity and short duration, then progress/regress as necessary for each individual.
In other areas of fitness such as nutrition, links between a certain substance (say cholesterol) and a certain outcome (for cholesterol, it would be heart disease) are sought through some discernible method. It is a theory that high cholesterol leads to heart disease based on the rate of occurance of heart disease in a population increasing as cholesterol levels in the blood increase. But again individual differences make it hard to prove. There are a small number of people with very high cholesterol levels that never develop heart disease. this makes some people question this theory. And some people use it as an excuse not to follow recommendations based on this theory.
We all do a bit of what has been called “trial and error”. But what we really mean is “trial and evaluated outcome”. Where we compare our results to the desired outcome and then modify the “trial” to get closer to the “desired outcome”. This is really “theory” and “testing the theory”, then adjusting the “theory” and “retesting the theory”. This goes on until we are satisfied with the “outcome”.
The biggest drawback of this system is that “we” aren’t always the best people to be doing this type of “testing”. In research studies, highly trained individuals are attempting the “testing”. And when people are being used to evaluate the “theory”, they are willing participants. For a fitness instructor to “test a theory” on their clients without informing the clients of the “test” and without gettng the clients’ “informed consent”, a line has been crossed beyond our scope of practice.
So, use your “theories” conservatively and progress the use of those “theories” cautiously.