“Dude, I am isolating the inner pecs with this exercise!” Now, this is interesting because bodybuilders have said this for many years and you can certainly feel parts of your muscle more involved in certain ranges or movements. Yet in the science, it never made sense as the muscle is totally supplied by a motor nerve and not sectioned as to be able to selectively recruit certain parts. However, there are something called non-spanning muscle fibres, which are muscle fibres that don’t span the entire length of a muscle. If they did then the entire muscle would contract and so you couldn’t isolate or bias an area. So, can you target parts of a muscle with certain exercises?