***Edited to add:
A year ago I began the push up challenge not being able to do one push up. I worked up to 100 push ups and now I make a point of doing 100 push up 3-4 times per week. Typically, I do 4 sets of 25 or 5 sets of 20. The following core set is what I am doing on the days I am not doing the 100 push ups.
I've really never found a core program that I absolutely can't live without. There are many good, even great ones out there, but with the amount of training I am currently doing with running, swimming, rowing, and perhaps spinning in the near future, spending another 30 - 60 mins in the weight room 3-5 times per week, or trying to vie for the DVD player and television in a home full of people, so that I can target specific muscle groups just is not feasible for me.
I have used P90X, Jillian Michaels, countless "Core workouts for runners" and various websites to try to hit my weakest areas. The problem is that many of these use more time than I can commit to them or require weights/balls/resistance bands and the like that don't fit in my purse or suitcase.
I am finding that the best way to get a good core workout in is to do it when I can. Oftentimes this is right before or after a run, after a shower, in between loads of laundry, or while waiting for one of the kids to be ready to be picked up. Sometimes I fit it in while working with my clients or if I just need a break from the computer work. My core routine needs to be quick, intense, and require no equipment except my own body weight coupled with a serving of "let's get this done!"
Over the last several weeks, I have come up with what I think will help me to achieve the fitness level I desire in the small amount of time I have during any given day to get it in.
Here is what it looks like from a basic structure:
Burpees (no hop, no push up)
Standard push up
No rest, directly into Round 2:
Burpee with push up
Triangle push up
Side plank (star position)
30 sec rest
Burpee with push up and hop
Push up with alternating leg raise
Opposite side oblique crunch
Opposite side Side plank (star position)
That's it. I do it as fast as I can, without compromising form, and with minimal rest in between.
I have left reps off so that this can be adopted if you choose to give it a try.
My workout today looked like this:
10 push ups
1 min plank
5 burpees with push up added in
10 triangle push ups
25 right side oblique crunches
1 min left side star plank
Rest 30 secs
5 Burpees with push up and hop (jump up at the end of the move)
10 push ups alternating leg raises
25 left side oblique crunches
1 min right side star plank
This is a bare minimum workout for me. I can do this every day if needed. On days when my time is EXTREMELY tight, which can be any day around here, I commit to only ONE ROUND and max it out. In that instance, I try to get in both sides of the obliques by either only doing the oblique crunches or drop the oblique crunches and add in the hip dip to the side plank, making sure to do them bilaterally. If I have more time and I want to add more reps, I do. Some days I try to max out everything the last round. Some days I will do decline push ups and/or try some one-armed push ups. I may also do the side planks with a hip dip in it. It really depends on how much time I have and what the demands of the rest of my workout schedule looks like for the day.
The most important aspect about this routine is that it is specific to what I currently need to strengthen and it can be done anywhere at anytime. All of that will help me maintain consistency.