A mathematical model for variations in the functional state of a living organism under external regular load

On the basis of the nonlinear model of the overdamped Duffing oscillator, the adaptation of the living organism to regular external loads (constant and periodical) was studied. It was shown that this model describes the stages of strain and resistance. In the resistance stage, a superadaptation phase may be observed, which exceeds by functional shift its asymptotic volume. This stage has a threshold character with respect to load. It was shown that the theoretical results coincide with the experimental data obtained under periodical loads. The conclusion about the existence of optimal load frequency, which leads to a maximum heating of the organism. The differences between the responses of organisms with strong and weak immunities to the harmonic actions were analyzed.