If you just train say kicks on your bag no punches just roundhouse kicks trying to get your form better trying to chop down on the bag just trying to over all trying to get your roundhouse kicks better. How long should you train for on the bag. Just kicks whats a good time to train them. 30 minutes 45 minutes a hour.I know it could get boring but I mix up my training. I'll just kick at times,I'll just punch at times and i'll punch and kick at times.