The question, "Can too much sex cause carpal tunnel syndrome?" is something patients ask me a lot - most times half-jokingly. As an expert in neuroscience and carpal tunnel syndrome, it's actually not such a bizarre question. It's certainly an interesting topic and worthy of serious discussion.

Your first response might be that the very idea is absurd. How can sexual intercourse and carpal tunnel possibly be related? But as it turns out, it's not so silly after all.

The possible relationship was first raised by Dr. John Zenion. He studied the many risk factors for getting carpal tunnel syndrome. Then he excluded occupational risk factors like working with vibrating equipment, lifting heavy loads, etc. Of the 8 non-occupational risk factors, 4 could be attributed to changes in a person's frequency of having sexual intercourse. How that association is linked is outlined below.

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Before understanding how it's possible that too much sex causes carpal tunnel syndrome, let's discuss what this disorder is all about.

Carpal tunnel syndrome is a type of neuropathy. That means a nerve is injured or damaged. In this instance, we're specifically referring  to the median nerve.

The median nerve is one of the major nerves of the hand. Among other functions, it sends sensory information to the brain. It caries feelings like fine touch, pain, vibration, temperature, etc. The nerve courses from the fingers, through the wrist joint, up the arm, and to the brain.

Wrist flexor tendons also follow the same course as the median nerve; from the fingers, through the wrist joint, and up the forearm.

For the greater part of their lengths the median nerve and flexor tendons have plenty of room next to each other. But when they funnel through the wrist joint, they all squeeze through a narrow passageway. This is called the carpal tunnel. (It's also where the name of the disorder comes from.)

Inside that carpal tunnel passageway, the nerve and tendons are packed so tightly together that the slightest disturbance of one is felt by the other structures. (See image below.)

When tendons become stressed (by overworking them) they tend to inflame and swell. Of course, swelling anywhere along the length of the tendon ordinarily poses no problem to the median nerve. But inside the tight carpal tunnel passageway there's no room for swelling. So as the tendons expand and swell, they push against the median nerve. 

Nerves don't like to be squeezed. Therefore, that squeezing is what causes all of the symptoms of carpal tunnel syndrome.

Eventually, without treatment, the squeezing continues more and more. Eventually, the median nerve is completely crushed. This is when carpal tunnel symptoms become much worse, called the severe stage of the disorder.

As the median nerve is crushed by swollen tendons, it produces specific problems we call symptoms. The symptoms occur in all of the fingers except the pinky finger. They also occur primarily on the palm side of the hand. The symptoms can vary from person to person, but generally include:

• Pain
• Numbness
• Pins & needles (tingling)
• Burning
• Soreness
• Weakness
• Itching
• Puffy feeling (without actual signs of swelling)
  

What does "too much sex" really mean? Most psychologists assert there's no such thing, provided it involves a normal and healthy relationship.

And when it comes to physical exertion, sex is relatively good exercise. In fact, men burn about 100 calories during sex. This compares to 276 calories burned on a treadmill.

But the evidence also suggests that when sexual intercourse is performed frequently, it increases the risk of carpal tunnel syndrome. The exact reasons are unknown. But Dr. Zenion suggests an indirect possibility:

The relationship is likely due to excess pressure you exert on bent wrists during sex.

If a sexual participant is obese or has a large chest circumference, it produces a heavier upper body. So does the condition of macromastia. This is abnormal enlargement of the breast tissue in excess of a person's normal proportion.

These conditions have the potential to produce excess pressure on bent wrists during sexual intercourse.

Certainly, the bilateral nature of carpal tunnel syndrome can be easily explained this way. About 87% of people who have carpal tunnel syndrome in one hand will get symptoms in the other hand within 6 months.

Why? Perhaps because most normal humans use both hands to support the upper body during sexual intercourse. Dr. Zenion says that makes this association quite plausible.

In addition, the bent (extended) wrist joint is like a time bomb. Hydrodynamic studies show that bending the wrist alone can increase the wrist's internal pressure 3-5 fold. So can bending just a couple fingers!

Now add to that pressure a person's upper body weight on the bent wrist during sexual intercourse. It's easy to see how that pressure can multiply several times.

As we've seen, carpal tunnel syndrome is fundamentally a problem of the median nerve being crushed by internal fluid pressure. It's only reasonable to assume that any added pressure (a bent wrist plus weight on the wrist) will add to the crushing force on the nerve.

Now consider the parallel between the incidence of carpal tunnel syndrome compared to the frequency of sexual intercourse during one's lifetime. Between the sixth and the seventh decades of life, the frequency of sexual intercourse decreases over 6 fold (combining male and female data).

Interestingly, the probability of getting carpal tunnel syndrome during that same age range falls 4-5 fold. Is this just  a coincidence? Perhaps.

But while there might not be a direct correlation, it certainly is curious that the incidence of carpal tunnel syndrome is proportional to the decline in sexual intercourse with age. Of course, other factors like some morbidities (which can lead to increased carpal tunnel risk) in addition to decreased libido (resulting in less frequent sex) may play a role.