Your central nervous system is the most vital area in terms of sports performance improvement. good to know. Training to failure using compound movements will overtax the nervous system and stop gains from being made. Need to know. Both of these statements are based around similar ideas and are expressed in ways that can be helpful to a trainer or trainee in developing strength programs. How do you know the difference between the two however and why is one good to know and the other a need to know piece of information?