I do at least 30 min per day 6 days a week. In my opinion a workout is too short if you are not sweaty, tired and sore. If you are going to the gym for a 10 min workout you are just wasting your time. You will never gain muscle or lose weight with a 10 minute workout. I have read in many articles that you should at least do 30 minutes for your workouts. Then you can go home and have a protein drink to repair your ripped muscles. Also please note that I not telling you to go to the gym 6 days a week like I do but at least do not cheat yourself out of your workout. In rushing through the workout you can injure yourself. You need to have at least a 5 minute warm up and then a 5 minute cool down.