Have been Kickboxing since the start of March at least 3 times a week and am still having trouble with my fitness i run for 20mins before the start of every training session which last an hour and half each but my cardio still isnt any where near as good as it should be, i just can't seem to get any better at running i am still as tired at the end of each run as i was when i started back in March and i've quit drinking, smoking and improved my diet.. i am a bit fitter but not much, i seem to have hit a wall. Should i start running on what are normally my rest days? i am afraid of over doing it and realise how important rest and recovery is but surely i must have to do more in order to improve? I'm not fit to run any more than 20min so increasing the length of run is not really an option as it will tire me out too much before training.