This is something that a dedicated martial artist or person who lives a healthy lifestyle should get at an intuitive level.
Through my time of getting my education, there were periods when I had to take a break from martial arts training. Getting through organic chemistry was one of those time periods. (I got two A+ grades, so made the absence worth my while.) However I always came back.
I distinctly remember what it was like doing kotekitae for the first time after a long absence. "Man, this hurts
!" But after about a month, the pain first became routine, and then evolved to pleasure. I actually had a dedicated student and self-described hedonist (martial arts, skydiving, skiing) who once described the phenomenon as being horny for contact. And he wasn't talking about sex.
When we engage in hard work, our bodies release endorphins. There are receptors in the brain which those chemicals lock into that stimulate pleasure centers and change our perception of pain. We have evolved to that internal neurohormonal system because getting out of bed in the morning and working the fields meant we fed our families and passed on our DNA. He who didn't get out of the hut didn't get the hot chicks, and so was eliminated from the gene pool.
There are cannabinoid receptors in the brain which THC binds to. This is the reason for a high. But there are short- and long-term consequences to stimulating those centers with exogenous substances.
The changes in brain structures indicate the marijuana users’ brains are adapting to low-level exposure to marijuana, the scientists said.
The study results fit with animal studies that show when rats are given tetrahydrocannabinol (THC) their brains rewire and form many new connections. THC is the mind-altering ingredient found in marijuana.
“It may be that we’re seeing a type of drug learning in the brain,” Gilman said. “We think when people are in the process of becoming addicted, their brains form these new connections.”
In animals, these new connections indicate the brain is adapting to the unnatural level of reward and stimulation from marijuana. These connections make other natural rewards less satisfying.
“Drugs of abuse can cause more dopamine release than natural rewards like food, sex and social interaction,” Gilman said. “In those you also get a burst of dopamine but not as much as in many drugs of abuse. That is why drugs take on so much salience, and everything else loses its importance.”
- Northwestern University Website
This is one of many reasons I have eliminated sugar, high fructose corn syrup, and salt from my diet. I have replaced those olfactory system simulators with myriad spices. I've now "rewired" my brain so I can eat 100% cacao - totally unsweetened dark chocolate - and really enjoy it. Regular chocolate now tastes like kids' food to me. Potato chips are too salty. Really good coffee on the other hand is wonderful - especially when served black. So are most healthy foods that my body really should be consuming.
This is a lot deeper than what you might surmise on first blush. I sent this article out to people on my research/analytics team, and most didn't get it. Methinks they were mostly in denial.
Not many people "get" me anyway, but...
I was at the gym last night, watching a middle-aged woman doing incline flies with 30 pound dumbbells. Not bad... She was there with her husband, who was spotting her. I went up and complimented her. After she whined about it hurting too much, I told her that continued training would make her crave it. She said she was too old for that. I looked at her straight in the eyes, and told her my age. It turns out I was 14 years older. Her jaw dropped.
There's a reason our bodies reward us for doing certain activities. When you short-circuit those reward systems, you get what you get. If you want to see the consequences of people who do this, go people-watching in any local Walmart. Bring your barf bag...... People of Walmart