What are you training for? Lately I´ve seen many noobs in the gym, where I usually train, doing some stupids exercises or simply doing them in the wrong way. On one hand, there are a lot of people who try to gain mass muscle in a few days, and on the other hand, there are a lot of gym´s coachs who don´t have the enough knowledge to supervise noob costumers. If you are new on this, I suggest you explore the web and compare several websites or videos with the purpose of deciding what kind of exercises are the best for you and how you can plan your routin in base your goals. You must know your body and your limits if you don´t want to injure any joint, that´s why make sure you are doing the exercise correctly if you want to see some results and don´t lose your health. Ask to the gym´s monitor and decide by yourself how you will do it, speaking of which, I saw people in the hospital because they did what their coach said them, so don´t be stupid! That being said I would like to boost everybody to do phisic exercise, it doesn´t matter if you run, walk, play football or whatever , just do it and you will perceive its benefits instantly.