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Are dark skinned computer workers more susceptible to muscle fatigue/ RSI/ eyestrain?

Almost each time I've worked intensively on the computer or read books excessively, I have developed severe forms of RSI, including extreme eyestrain. 

RSI begins with badly fatigued muscles and then leads to spasms. Apart from discovering/ inventing methods to relieve severe RSI and eyestrain symptoms I've been asking a question over the years about what happens at the cellular level in the body to cause these spasms. For if we know that, then a medicine could be invented to alleviate muscle fatigue/spasms.

Unfortunately, the scientific literature on this subject has generally been less than useless, and despite my fairly extensive study of such literature I did not find any "medicine" that could help, at the biochemical level, reduce muscle fatigue and RSI symptoms.

For many years I thought that spasms were a consequence of lactic acid which tore muscle fibres and created local inflammation. If so, there was apparently nothing one could do about it.

I was wrong. Lactic acid has since been shown to have uncertain effects: 

it is uncertain if lactic acid reduces fatigue through increased intracellular calcium or increases fatigue through reduced sensitivity of contractile proteins to Ca2+ [Wikipedia]

Instead, in 2008 it was discovered that muscle fatigue is caused by issues related to "calcium flow inside muscle cells".

Ordinarily, ebbs and flows of calcium in cells control muscle contractions. But when muscles grow tired, the investigators report, tiny channels in them start leaking calcium, and that weakens contractions. At the same time, the leaked calcium stimulates an enzyme that eats into muscle fibers, contributing to the muscle exhaustion. [Source]

muscle fatigue is caused by calcium leaking out of the muscle cell. This causes there to be less calcium available for the muscle cell. [Wikipedia]

Calcium inside of muscle cells is usually kept contained. When it is allowed to leak out into the cell that calcium itself is toxic, turning on an enzyme that chews up muscle cells. Once the leak starts, it's a vicious cycle. The calcium leak raises levels of damaging reactive oxygen species, which oxidize RyR1 and worsen the leak. [Source]

My muscle fibres are being eaten up by an enzyme (due to heavy static load imposed on them by computer use, including looking at the monitor). There is, however, no comprehensive understanding of the biochemistry of muscle fatigue yet, and hence no medicine to deal with this calcium leakage issue.

I'm now considering a hypothesis. It is linked to the recent documentary that I've seen (and discussed), Origins of us, and this new konwledge I've acquired about calcium system disruption.

This is a pretty wild hypothesis. I don't claim to understand the molecular physiology of muscles, but in science, you try out a number of things based on potential linkages and patterns. So this is worth exploring. I'll send a link to this blog post to the primary researchers on muscle fatigue and if they think it makes sense they can try it out. In the meanwhile, I'll experiment on myself.

Facts that could link together

FACT 1: Origins of us shows that we evolved as sun-runners. We had a niche in the savannah for gathering our food by killing animals between 11 am and 4 pm in the HOT SUN. Our super-efficient cooling system (sweat glands) can help us outrun any creature on earth at that time of day in the hot African plain. That was our comparative advantage as a species. Plus some trickery (a smart brain).

Being a sun-runner gave us a dark skin to prevent over-exposure to the sun. However, let's not forget a key point. That we were "designed" to get our Vitamin D needs from the sun, and Vitamin D is crucial to proper absorption of calcium in the body. And there is some evidence to suggest that: 

in adults, vitamin D deficiency can lead to osteomalacia, resulting in weak bones. Symptoms of bone pain and muscle weakness can indicate inadequate vitamin D levels, but such symptoms can be subtle and go undetected in the initial stages. [Source]

Now, here's where the dark skin comes in. Those of us with a dark skin who work indoors on computers the whole day do not get enough sun on our skin. We are almost certain to have serious deficiencies of Vitamin D. This could affect our muscles both directly and through the calcium system (sorry, I can't explain why this last bit might be true! – that's just my speculative hypothesis).

FACT 2: I do not generally go out in the sun. I exercise in the gym, and spend most of my time indoors. My blood tests over last few years indicate exceptionally low Vitamin D levels. And I've experienced what (I think) is particularly high vulnerability to muscle fatigue/ RSI/ eyestrain.


Putting facts 1 and 2 together, it is possible that dark skinned computer workers who do not get enough sunlight would be particularly vulnerable to muscle fatigue and spasms.

A personal experiment that I'll now undertake:

I well understand (after a decade of personal experience and experimentation) solutions which can significantly ease extremely severe muscle spasms (RSI/ eyestrain). But now I need to thoroughly understand the molecular and cellular system and determine ways to reduce muscular fatigue at the atomic level. That will hopefully provide the more complete solution.

To begin with, given the HUGE GAP of HUMAN KNOWLEDGE in this area, I will now increase my intake of Vitamin D significantly through direct sunlight and increase my calcium intake as well. Should that help, it might point to a more effective way to relieve muscle spasms.

If you come across any PUBLISHED scientific literature on this topic, please send me the link.

If we are going to do so much computer work as a species, we'd better learn more about our body and ensure that we optimise our body for computer use. It is clearly NOT designed for such excessively sedantary work that imposes huge static load on a range of muscles.

Andrew Marks, the world's leading researcher on muscle physiology.


  • your body is meant to get its Vitamin D from sunlight —not from supplements [Source]
  • It takes light-skinned people only a few minutes in the sun to receive enough UV-B rays to make Vitamin D. Darker-skinned people may need to be in the sun 5 to 10 times longer to reach the same levels of UV-B exposure in order to create Vitamin D. [Source]

vascular smooth muscle membranes from spontaneously hypertensive rats leak calcium at a rate that is only partially compensated by the calcium pump.

 "normal people essentially acquire a form of muscular dystrophy with age"

  • mutations in RYR1 cause excessive amounts of calcium to leak from the storage compartment and trigger uncontrolled muscle contractions [Source]
  • Studies have shown that optimal Vitamin D levels prevents leaky calcium channels inside muscle cells. No other drug is needed. [Jake, here] – Note: I could not find any study that shows this. Much appreciated if you could refer me to such a study.
  • Of 150 patients who visited an inner-city clinic in Minneapolis between 2000 and 2002 with a complaint of musculoskeletal pain, 93 percent were deficient in vitamin D. [Source]
  • Many proteins are regulated by vitamin D in the body, thus muscles, which are predominantly made of protein, are not regulated correctly when the body experiences a vitamin D deficiency. [Source]
  • vitamin D will improve athletic performance in vitamin D deficient people (and that includes most people) [Source]
  • a substantial increase in muscle activity happens after radiation of larger portions of the body with an artificial sunlamp; that this performance increase is not caused through local – direct or indirect – effects on the musculature, but through a general effect. This general effect, triggered by ultra-violet irradiation, is caused by a systemic effect on the nervous system. [Source
  • Wicherts and her colleagues found a linear correlation between vitamin D and neuromuscular performance [Source]
  • The Vitamin D Solution: A 3-Step Strategy to Cure Our Most Common Health Problems by Michael F. Holick Ph.D. M.D.
  • Power of Vitamin D: A Vitamin D Book That Contains the Most Comprehensive and Useful Information on Vitamin D Deficiency, Vitamin D Level by MD Sarfraz Zaidi  [I've purchased all these three books today and will review the scientific evidence carefully]
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Sanjeev Sabhlok

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6 thoughts on “Are dark skinned computer workers more susceptible to muscle fatigue/ RSI/ eyestrain?
  1. Vishal Kumar Singh

    There could be some truth in your theory. I was having persistent headache and eye strain. This summer I was out most of the time and my headache disappeared.

  2. allwyn

    Well I have brown skin and I too don’t get much sun light. I am also very THIN and TALL(5.11ft). Do these factors come into consideration. Height mostly does what about WEIGHT? I mean I have less wt than I should have if we go my the charts.

    I also have both RSI and EYE-STRAIN(described below) and both are pretty severe if you ask me.

    RSI: my shoulder and neck and lower back muscles infact my full back has tight muscles which also gives me tingling-pins-needles and stiff/tight like pain in elbow, fore arms and wrist even fingers. This happens withing mins of sitting on the computer or using my android phone(while using d swype keypad on it). I’m following all your tips for it.


    eye-strain: which starts almost instantly once I start reading on comp or pdf on my phone and watching TV. For this too I’ll follow your ideas after getting my neck muscles loose with myotherapy as you say then foam roller.

  3. Sanjeev Sabhlok

    Allwyn, if this hypothesis is correct (and that’s a big if!), then you might have Vitamin D deficiency and therefore problems with your calcium system. I could be entirely wrong, so don’t take this as more than a hypothesis. Get blood tests done before you start consuming more of it. Having said that it appears that the type of Vitamin D obtained from the sun can’t become toxic. The body generates just the right amount. People with a darker skin usually need a longish time in the sun to get their Vitamin D, it appears.

    For eye-strain – I’ve now brought down the symptoms very significantly and am documenting the various eye-exercises that helped me. Do keep a watch on Time permitting I might make a short video and upload on youtube.

    Both RSI and eyestrain are curable (although these will recur unless one gives up using computers/ reading altogether).

  4. Sanjeev Sabhlok

    Allwyn, I’ve updated the eyestrain blog for the list of exercises that have been helping me. If you find any others, please let me know. I did record a video of these exercises but the recording was defective. I’ve got no more time to devote to this, so hopefully the description of the eye exercises is clear enough.

  5. Akash

    Hello, did your experiment work out? Did vitamin D supplementation help out with your RSI? I have severe RSI very similar to Allwyns which started after I had a bad bike accident, and recently discovered I have low vitamin D 4.5 Ng/ml. So am wondering whether there is indeed a correlation as you have hypothesised.

  6. Sanjeev Sabhlok

    i did try but have concluded that Vit. D is not a major issue in RSI/ eyestrain. Maybe a very minor issue. 

    It appears it may have other health benefits.

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