..for most people, especially those who don’t do enough of it. Why does it ‘feel bad’ and is hard to do psychologically?
In: Biology
It is a stressor for muscles, bones, and ligaments that aren’t adapted to such activities. So they break down a little bit if you put them through these stressors, but the bright side is they grow back stronger as a result, making you more fit and making it harder to get sore from the same routine movements once you’ve recovered and adapted.
In short, it is work on the body. And work takes energy. The body likes to preserve energy, so not working is comforting, but avoiding it allows your body to weaken overtime and get “out of shape”.
Physical exercise means use of energy, and back in the hunter gatherers era there was always a scarcity of food. Therefore they try to exert themselves as little as possible so they won’t starve all the time. This has basically carried over to us from our ancestors
You kind of answered your own question when you said “when you are not used to it”, and the answer is exactly that, and it is called conditioning…
Physical condition is the body attaining fitness through adaptation and improving. Doing something we are not accustomed to, or which makes us uncomfortable is painful, and our brains will fight us on it (physiological aspect).
A 10k run would be terrible for someone who is overweight and has not run a 10k before or done any physical exercise.
That person would need to attain the fitness and conditioning to reach that distance, by building up cardio (heart) and vascular (lung) endurance, along with muscle and ligament strengthening and weight loss, eventually becoming competent.
The body will adapt to such a point that the 10k would no longer be uncomfortable and psychologically, it would become enjoyable.
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