The “Gate Theory” is what I had in mind. Also the areas in the brain that interpret pleasure and pain abut. So there is a close connection between the two.
One always feels better after vigorous exercise. However, I think different principles apply there. It’s part emotional, but the body has been well oxygenated, which IMHO helps for the well being.
I hate to contradict anyone who has already posted, but I’m an extreme masochist so listen up. Pain, submission, and being restrained turn me on in a sexual setting, like most masochists. like most, being dominated by a partner nonsexually is not enjoyable. However, I am unlucky enough to be turned on by random pain, which is not normal, and by being restrained. I am the exception to the rule because of being turned on by nonsexual pain. I burned myself on a friends motorcycle once. The burn hurt, but then it felt rather good and I did get wet. I have yet to hear of anyone else whose body reacts that way to pain, regardless of time and place though.
Question.
What, then, is the definition of masochist?
Does it always have a sexual component, and does it always have to happen with someone else in the room?
Here is why I am asking. I have never considered myself a masochist, but my wife told me she thinks I like self induced pain. Which kind of startled me. The only Self induced pain I partake in is when I have to perform some type of self surgery. Usually it is an ingrown toenail, but it can be and has been other things.
I have a very high pain tolerance, but I don’t want to beat my wife or be beaten myself during sex. However, I do get satisfaction when I dig out an ingrown toenail, because the release of the pain Is such a relief. I tend to get ingrown toenails a lot more than the average person, but I’ve only had to go to the emergency room once to remove one. I take pride in that.
Does that make me a masochist, or just someone who can handle pain enough to get a knife and tweezers and cut into a very sore toe in the hopes of finding and releasing an ingrown toenail) and the pain that goes with it?
This sounds like you might be a zombie.
You’re not a masochist. A masochist gets sexual enjoyment through pain. The pleasure of the sexual arousement overrides the pain nerve paths. But you are a zombie. 
A zombie? I can live with that!
I believe we all tend to handle pain different ways. I have had a pinched nerve in my neck that causes extreme pain in my left arm. I have had this condition for over 20 years and it was somewhat relieved by surgery. I can turn that into a euphoric high of sorts now and at some level get pleasure from it. Same way with an artheritic knee. The pain is far too intense to go to sleep until I get into a zone with it. Kidney stones, apendix, bruised liver no way I could turn them into pleasure zones.
I have a 77 yr old buddy into s&m. He is impotent and has a bad heart yet he has no shortage of young and older women that come to him for his torture treatments. He spcializes in small whips and nipple pinchers things like that. I talk to the girls all the time and they tell me they have orgasms with no sexual contact, I am skeptical.
What if you stub your toe on purpose in a sexual setting? Or if your partner gives you paper cuts with you overdue bills?
I see that this post is an old one, but as I stumbled on it in the first few links searching for ‘masochism and not feeling pain’ and it has few quality responses.
Do we experience sexual pleasure from pain outside a sexual encounter?
All people feel pain differently. All masochists have their own personal levels of sexually enjoyable pain and a threshold which is just ‘pain’. That threshold may be fudged with a bit during a sexual encounter, but there is definitely a baseline in every day life.
But DO we experience sexual pleasure from pain not arising from a sexual encounter?
I can’t answer for people who are less of a masochist than I am. For myself and others whom I would consider a true masochist, I would say yes.
Before I realized that I had stress fractured my foot, I would intentionally twist my foot around to increase my pain. I enjoyed it sexually as others might enjoy a kiss on the neck.
I once was covered in poison ivy so severe that 75% of my body from head to toe - including my scalp. As I am highly allergic to poison ivy and I had developed a severe reaction to steroids, it took a very long time to get rid of and while I struggled to get rid of it, it worsened torturously before it got better. During that time, I would intentionally take piping hot showers, even though I had read that it would spread the poison ivy, knowing that I might be spreading it and not caring because the sting - the burn and pain of it - felt so good that I had orgasms from the hot, hot water hitting places like the underside of my forearms, my neck, the back of my knees, my feet…well, everywhere, actually. The PAIN was orgasmic. I also cried - because it was an exquisite suffering. It had nothing to do with sex. To this day (actually not long after poison ivy for 16 weeks straight), if I could get rid of it quickly, I would purposefully inflict poison ivy upon myself for the sexual enjoyment of it. Truly.
I have been cropped to bruising, slapped unexpectedly and enjoyed it (though in good fun at the time!), spanked for my birthday (that one was awkward - friends I wasn’t into that way giving me my licks), even orgasms in a sexual setting from things that I REALLY did not enjoy at the time.
I do enjoy mundane things like bruises (which I thought my fractured foot was til I learned otherwise), scrapes, the odd mild burn, even more painful injuries.
No, I do NOT enjoy stubbing my toe or paper cuts - those are especially unpleasant and WOULD require a sexual environment to be anything else…but they could be sexual.
Masochism is a switch. Pain is a nerve telling your brain to take caution or risk further injury. If the message is changed, if the brain is taught to tolerate a certain amount of ‘injury’ without the alarm bells of ‘pain’, the sensation non-masochists feel, that pain you experience, becomes just another sensation. However, a very hardcore masochist, like myself perhaps, can exceed the limit of their acceptable pain tolerance and have a sexually enjoyable experience anyway because the pain itself is the cause of the orgasm - like the poison ivy I had.
This morning’s post is brought to you by a scratch my cat gave me on the foot that went unnoticed til I saw the drop of blood.