Got in and really didnt feel up for a run but decided to do some core work instead. Started off with my usual routine of 20 crunches followed by 20 reverse crunches. Three sets with 1 minutes rest between each one.
Then some really simple free weight exercises with my weights that i use for running so nice and light, followed by some resistance exercises.
To finish 20 press ups with chest touching the ground every time and then a few stretches off.
Since incorporating a core session a week i have felt much stronger especially when ascending so it obviously has good effects as long as you just tone and dont put on bulk muscle.