Strength is commonly defined as an athlete's ability to overcome specific and measurable different types of resistances. The strength itself is conditioned by the reactivity of muscles, which means that it is actually conditioned by the force exerted by the muscle when it responds to a specific stimulus or impulse. It is not unambiguously defined, but depends on the type and form of manifestation during particular sports efforts. During weight training, the athlete's muscular system is actually performing the strength training because it needs to produce a force that will oppose the specific external load. In order to be able to monitor the development of strength in weight training, it is necessary to define specific load parameters, as well as specific expected outcomes that are aimed to be achieved with specific loads. This paper describes the concept and types of physical strength, as well as the expected progression of strength development in active athletes. Factors that influence strength development, as well as biological predispositions and limitations in terms of strength development, are also discussed. The paper defines the concept of weight training, as well as the types of weight training applicable in the strength development of athletes. At the same time, in parallel with the influence of this form of training on athletes, its effect on the training of recreational athletes is considered, for whom the first priority is not a measurable result or competitiveness with other professionals, but their own health well -being, strengthening their own physical strength, together with all other benefits mentioned in the paper.