This allows us to be more effective in predicting outcomes. A 21-year-old male is much more active than an 85-year-old male. If we compared the strength of this 21-year-old to the strength of an 85-year-old male, even if there was a significant strength deficit, it would still look pretty good. By comparing him to another 21-year-old, we get a true representation of where his strength is and where it should be compared to other 21-year-olds his age and weight. By comparing you to someone your age, weight, and gender, we are able to more accurately predict your response to our treatment.