All types of physical practice, in fitness or any other sport, must begin with correct warming up. This activity, together with relaxation and the main stage, are the three essential parts of the training. The types of warming up can vary a lot in length, intensity and structure of exercises, according to the sport or the training you want to start. Although there are many kinds of warming up, all of them have in common two distinct stages. The first stage concerns general warming up, whose purpose is to gradually prepare the whole body for the effort which will follow. The body temperature also increases. At this stage, the inertia of the body is easily removed through aerobic exercises (running, cycling, etc.). This stage should not take more than 5-10 minutes; otherwise it will change into a real aerobic training. It is well known that during aerobic effort the body consumes a lot of glycogen, so, especially before force training (anaerobic), there is the risk of running out of energy. The second stage of warming up is specific to each sport. This stage aims to warm up the main muscles and joints involved in the effort, but also to anticipate, by simulation, some movements from the main part of the training. This stage can be longer than the first one and includes different types of gymnastics for the joints, jumping, exercises at greater speed, stretching, etc. However, this stage shouldn't be very long either, because the sportsman needs to save physical energy and to avoid mental stress. In many sports (target shooting, fencing, tennis, etc.), mental stress can be bigger than physical effort. These two stages of warming up must come one after the other very strictly. It is forbidden to switch their order, and also to skip one of them. Unfortunately, it is common in sport to skip the first stage and do just specific warming up, which is considered more important. This is a big mistake, because this type of exercises does not rise the body temperature as much as the ones involving minimum aerobic effort. The result is that the body will be much more rigid and a lot less prepared for the main part of the training. There are cases, especially in sport games, when both stages of warming up are abandoned. Kicking the ball or passing a few times are supposed to replace a thorough, but boring warming up. Not doing the warming up correctly or, worse, not doing it at all increases the risk of having accidents during training or competing. Possible accidents range from simple ones, like pulling a muscle or cramps, to some really bad ones (ruptured muscles, hernia, sprains, dislocations, etc.). Even if, luckily, such accidents do not happen, the body will experience a dramatic decrease of efficiency in performing the exercises. It is very important for beginners to do the warming up. If they do not ignore it when they take up sport, they will form a habit of warming up and will, hopefully, keep this habit as long as they do sport. They must not assume the false idea that, being beginners, they shouldn't exercise so intensely. All these problems are traps that correct warming up can definitely avoid.