[The body's responses to extreme exercise: biochemical aspects].

: Experiments on animals and clinical studies in athletes have shown a negative impact of extreme exercises on the physicochemical characteristics of biomembranes. The resultant decrease in the activity of different isoforms of the multienzymatic system of hepatic cytochrome P450 may underlie, firstly, the formation of a vicious circle of increases in the microviscosity of biomembranes and membrane-dependent processes and, secondly, the lowered resistance of athletes to chemical environmental factors, which should be borne in mind during the professional activity of high-class athletes.