Here's a little variation on the hangboard endurance program that I posted here: Hangboard Workout 002
In this one you do the same sets of hangs, with your feet up on a chair, on a suitable hold (I use a sloper that gives me a deep pump but is easier on the fingers joints than an edge or crimp) but instead of just resting in the off sets you do 10 v-sits (or leg raises, or crunches, or mix it up however you like it, just 10 reps of a good core exercise) then do either star jumps (jumping jacks) or skipping or jogging on the spot, etc for the remainder of the rest (be sure to push hard on whatever cardio you choose to get yourself breathing hard and your heart pumping fast).
Follow the instructions in the previous workout for the hangs, but essentially you are using a chair and doing them like this:
I did this workout today with 1 minute hangs followed by 1 minute of the core + cardio combo and did this 15 times for a total of a 30 minute workout.
Now the reason to use a chair is that it takes some of the weight off from doing a normal dead hang and allows you to complete the full 1 minute reps and the required number of sets by allowing you to vary the resistance by moving the chair closer or further away as needed. It also simulates the full body connections and core tension used from fingers to toes when climbing on steep terrain.
Adding the extra core workout and cardio to this endurance workout helps to simulate more closely the conditions we find ourselves under when climbing close to our maximum - core starting to get tired, breathing hard and fast, heart racing - which means your body is having to perform the endurance hangs in the workout under conditions more closely resembling that of real climbing conditions.
Now go get into it!