The essence of a sports training includes not only developing the skills necessary in a chosen sport but also particular care about athlete's health. This issue should be taken into account especially in case of children and youth engaged in sporting activities. In the paper there are issues connected to the control of physical effort abilities in the sports training of young football players and the assessment of the reaction of the body to physical exercise in city smog conditions (the environment of the city of Kraków) and clean air conditions (the environment of the town of Głuchołazy). This paper shows that, when assessing physical effort, one can consider not nly the results of physical tests but also the reaction of the body to a given physical load. One should remember that physical load depends not only on the methods used and the range of intensity, but also on the environmental conditions, like the quality of the air. Determining the reaction of the body to physical load (performance tests), taking into account the conditions in which the training takes place, prevents overloading and sets directions for rational sports training. The analysis of the results of the study leads to three main conclusions: (1) The planning of sports training has to consider not only the methods and means of the training but also environmental factors (air pollution); (2) Physical effort in smog conditions should be done with the use of antismog face masks; (3) The arrangement of sports training (particularly for youth) should strictly take into account the environment in which the training takes place.
Keywords: city smog; monitoring; physical performance; sports training.