If you are reading this, odds are that “screen time” takes up a lot of your daytime. You browse the internet, check your email, type up a document, maybe play a game or two. These activities are not strenuous; upon doing them, you are probably sitting, relaxed.
Anatomically speaking, not much is happening—right?
Actually, computer use is a full-body affair. It starts with the fingers, extends through nerves and tendons up the wrist, to the shoulders, neck, and down the spine. Products are made, industries are formed, and fields of study devoted to understand the intersection of human anatomy and screen time. Underlying them all is the basic assumption that humans did not evolve with computers and could benefit by learning how to use them in an anatomically sound way. In short: good posture is key!
Let’s start in the arm. Beginning in the brachial plexus, the median nerve runs down the arm, towards the hand. It passes through the carpal tunnel (an anatomical space in the wrist), providing sensation to the thumb, index, and middle finger. The median nerve powers several muscles, including those that flex the wrist. When the median nerve repeatedly becomes compressed (through, for example, wrists that tilt upwards on a keyboard, or through consistent finger extending), there is less blood circulation and less nerve conduction. These symptoms can lead over time to carpel tunnel syndrome.
Yes, poor posture has implications for your anatomy. Source: https://www.spineuniverse.com/
And then there’s the “smartphone pinkie.” The smallest digit bears most of the weight of a smartphone-in-hand. The weight on the pinkie, combined with the turned-in position of the wrist to tilt the screen towards our faces, can cause strain on the ulnar nerve. The ulnar nerve runs from the armpit to the pinkie side of the palm.
After the smartphone pinkie is the "cellphone elbow." Perhaps you have felt cellphone elbow in bed at night, holding up the phone to watch a movie or speak with a loved one. The prolonged bending of the arm means that your shoulder rubs against the ulnar nerve, causing ischemia (shortened blood supply) and tingling in the forearm. One study found that cellphone use caused a 70 percent increase in strain on the ulnar nerve (fun fact: your “funny bone” is really the ulnar nerve).
Poor posture has consequences for shoulders, neck, and back, too. Some physical therapists have seen such an uptick in the general muscular imbalance caused by poor posture that they have given it a name: “upper crossed syndrome.” That’s when “tight” muscles such as neck flexors overlap with weaker muscles in the upper back and shoulder blades, such as the rhomboids and trapezius muscles (hence the imbalance).
Extreme cases manifest in the human body with a forward head posture, increased curve of the neck, elevated shoulders, and a rounded upper back. These tend to manifest later in life. But let’s be honest: left unchecked, anyone can become an “extreme case.” We all could improve our postures, and we can take steps to make our relationships with devices less cumbersome on our anatomy.
This page elaborates on repetitive strain injuries (RSIs) commonly caused by computer use and offers ways to avoid them. And in the meantime, we can heed the advice of our mothers:
Don’t slouch and sit up straight!