Posted on April 6, 2016
Benefits of a Vertical Mouse
Here on 9 to 5 ergonomics, I’ve reviewed a number ergonomic mice that are designed to put the wrist in a more vertical position. In those reviews, I’ve mentioned a more vertical wrist position as a beneficial feature, but I realized that I’ve never gone into the specifics of why that is the case. This post is all about getting specific on the benefits of using a vertical mouse.
Neutral Wrist Position
It may seem intuitive, but consider the natural resting position of the wrist. When your hands fall to your sides, they likely do so with your thumbs pointed down and forward. As you bend at the elbow so as to form a 90 degree angle, the most natural position is for the wrist to remain neutral, meaning that the thumbs end up pointing forward and up.
Now, consider what happens with a typical mouse. In order to grip the mouse as it lies flat on the desk, the wrist and forearm must pronate, or rotate internally. Pronation of forearm reduces the joint space between the ulna and radius, the two bones making up the forearm, thereby putting the wrist in a relatively uncomfortable position.
How to Avoid Wrist Tendinitis
The real benefit (or downside depending on your point of view) of using a vertical mouse is that it lets you cheat a bit when it comes to mousing technique. In my experience, the most common injury that can result from a lack of proper mouse usage is wrist tendinitis. In particular, tendinitis of the flexor carpi ulnaris, a tendon located on the anterior of the forearm.
Tendonitis of the flexor carpi ulnaris tends to occur when the wrist is repetitively put into a position of extreme ulnar deviation. That is, the wrist is moved repetitively in the horizontal plane to its extremes. As one study found, typical average ulnar deviation during non-mouse usage is in the range of 2 degrees. However, when working at a computer, that number can go as high as 30 degrees. In other words, when you mouse exclusively from the wrist, you are putting your wrist in an unnaturally extreme position. When you do it excessively, it tends to result in tendinitis. That is why, as I described in my post on how to use a mouse properly, it is important to mouse with your whole arm.
Vertical Mice: A Temporary Crutch
Vertical mice turn the motion of ulnar deviation into wrist extension instead. Because the wrist naturally has a greater range of motion in extension and flexion, it is believed that a vertical mouse can help prevent tendinitis. That said, mousing from wrist is probably still a bad idea. Whether it is wrist extension/flexion, or ulnar deviation, by resting your wrist on your desk or mouse pad, you are still utilizing your wrist more than necessary, which may put you at risk for developing a repetitive stress injury.
The theory behind mousing with your whole arm is that the range of motion in any given joint will be minimized. In robotics, there is a concept known as degrees of freedom. In essence, a degree of freedom is a parameter of configuration that may define the position of the mechanical system. If that’s too technical, then think of it as the defined position of each of your joints at any given time. The wrist is an amazing joint in that it has 3 degrees of freedom: pitch, yaw and roll. The arm, on the other hand, has 7 degrees of freedom between the shoulder, joint and elbow. Now, as simple example, lets say that you need to move the mouse 4 inches in order to move the cursor from one corner to another. When you rest your wrist on your desk or mouse pad, it means that you are limiting yourself to just 3 degrees of freedom. As a result, the entirety of the 4 inch movement must be produced by the wrist. Because the length of the hand is relatively short, it means a large range of motion in the wrist is necessary. In contrast, by mousing with the entire arm, it is possible to utilize all 7 degrees of freedom. Because the humerus, radius and ulna are longer than the hand, it requires less range of motion in any given joint.
So, save yourself from injury and teach yourself good mouse habits from the get go. A vertical mouse may be a good crutch to use at first, but in the long run, your body will thank you if you mouse with the entire arm rather than just the wrist.