Technique in weight training is very important for achieving the expected progress, but also for protecting the body of the sportsman. The first important thing is to learn correctly the basic movements. In this type of training there is a kind of classic set of exercises, which the sportsman needs to master from the beginning. This set includes exercises with free weights (dumbbells and barbells). While training with these, the movement is not imposed by any machine. When executed without the supervision of a fitness instructor, it is possible that these movements are done in a wrong way, a situation which increases the risk of accidents a lot. One of the most frequent mistakes is an incorrect position of the spine. Some exercises (bench press, barbell curls) could involve exaggerated arching, while others (sit up bend, dead lift, squats, etc.) involve unjustified flexing (hunching). These wrong positions can lead to unfavourable stress exerted over the spine, knees or shoulders. Besides, they can direct the effort to other groups of muscles than the ones intended. The result is that none of these are properly trained, because no exercises specific to the muscles are performed correctly. In such situations, the sportsman will only feel exhaustion in all his body and will not be able to direct and localize the effort in the zone which a particular exercise should mobilize. Another example of wrong technique is exaggerated swinging for exercises which do not need impetus. This happens most often while raising the weights laterally for working on the deltoid muscles, when the sportsman wrongly flexes the knees and uses the lumbar muscles, arching his back too much. Other mistakes are made when catching the bars. In the case of pull up, for example, and of pushing from behind the neck (for the shoulders), a too narrow catch will place the scapular-humeral circulation into a non-physiological, stressing position. Exaggerated bending forward during squat will force the spine, while lowering the thighs below horizontal position will stress the menisci. Rowing from bending position and stretching back must be done with the back in extension; otherwise the risk of slipped disc might appear. Not using a belt when lifting very heavy weights can determine slipped disc, but also inguinal hernia or rupture of abdominal muscles. The technique of breathing must be understood correctly. Breathing in instead of breathing out, blocking the thorax or not can affect the sportsman a lot. Generally, the sportsman must breathe out during the most difficult part of the movement and must breathe in during controlled coming back in position. Apnoea (blocking of the thorax) must be used only in the case of lifting heavy and very heavy weights; otherwise it is not justified. While making aerobic effort, it is necessary to have a particular breathing rhythm, a pace which can vary according to the cardiac frequency and lung ventilation. All these examples support the idea that the presence of the fitness instructor during training is absolutely necessary.