1. Training and stress
As we know, our body strives to keep its diverse parameters (water content, ion balance, nutrient content, sleep quantity, temperature) within fairly stable ranges. The effects which move it out of these ranges act as stress factors. The body tries to respond to such factors, and tries to stop itself going outside the optimal ranges, either in a negative or a positive direction in the first place; but once it goes beyond them, it hurries to restore the previous values as soon as possible. However, if the stress factors persist, then the body tries to shift the given parameter values towards the direction of the stress effect, so as to more easily bear the stress factors when they arise again. Thus, this response effectuates an adaptation over a longer term. So what is training, really? During training, we expose the body to repeated physical stress on purpose, in order to induce its adaptation response, and through this, to cause changes in certain of its physiological-physical parameters.
It is important, however, to emphasise, that adaptation has three essential conditions. The response of adaptation will only be induced if the causing effect is within an optimal range. To a stimulus which is too weak – like a 25 metre run for the bus once a week – the body will not react with an adaptation response. But if the stress effect is too strong, a unit of the body will be harmed, or, the individual can even die because of the effect. Some are capable of running – ultramarathon – distances of more than 200 kilometres in one go, without standing halts, and they accomplish this in approximately 24 hours. It is quite probable, however, that without developing gradually, beginning immediately with such a distance, none of them could have reached that performance, because the overloading would have caused severe impairments in their body right at the beginning. A key factor of a successful adaptation response, besides the optimally chosen loading, is also the optimal resting period. During this period, the body regenerates from the effects of the single loadings, and it sets its parameters involved in the loading to a slightly higher and stronger level (this is called overcompensation; Radák 2016). The third important factor is regularity, since the performance of the body will not really change for a single load. The sum of many tiny adaptation reactions will lead to perceivable and measurable physical and physiological changes, which together are called fitness. So, as a result of the process, the performance of the body will increase in the given activity, and this generally affects performance in other activities as well.