The core is key when it comes to being fit. Everything surrounds and depends on the core to perform to optimal potential. I used to workout my abs everyday. After my workouts and on rest days. I remember reading that abs are a muscle group that was meant to be trained everyday. So that is what I did. However, I was not getting the results that I wanted when performing this routine for the core. I wanted more definition and it was just not working. In turn I eventually started decreasing the amount of times I worked out my core each week. I would perform a core routine either after a lifting session, after a run, or alone on a day maybe 3 times a week. I definitely saw the results I was looking for shortly after. I realized that my abs are just like any muscle group where they need optimal rest in order to recover and develop properly. One of my go-to core routines is the 8 minute abs. I usually try to finish it in around 6 minutes because I decrease the rest time but adjust the recovery time based on your level. It is a great ab workout when you are short on time. If you decrease the rest period enough it almost like a burnout. Below I posted a link to a youtube video going through the routine. I would recommend having around a 15-30 second rest in between the grouped exercises. I hope you enjoy!!