training the core should not always be isolation exercises. sometimes you need to challenge the core by adding stability and balance challenges that come from total body movement. these total body movements also help you use a lot of other muscles in your body as well so they are a great tool for increasing cardiovascular fitness, fat burning, mind-muscle connection, and stability while being time-saving. bear crawl and spider crawl help you not only in developing your frontal core muscles(like rectus abdominis and obliques) but also in developing the deep spine muscles like transversospinalis and paraspinal muscle group.