Armrests are designed to serve a supportive function in office ergonomics, but their effectiveness depends entirely on proper adjustment and user behavior. When correctly utilized, armrests aid a healthy seated posture by maximizing comfort and minimizing the risk of injury during long periods of sitting. However, when misused, they become a source of strain and discomfort.
The Primary Role of Upper Body Support
The fundamental benefit of armrests is their ability to offload the considerable weight of the human upper limbs, which account for approximately 10 to 13% of total body weight. When unsupported, this weight creates a static load that primarily strains the upper trapezius muscles, leading to muscle fatigue and strain in the shoulder girdle.
By providing a surface for the forearms, armrests transfer this load from the active muscles to the chair structure. This reduction in muscle activity in the shoulders and neck significantly decreases the likelihood of developing tension headaches and chronic upper body strain. Forearm support reduces the static muscular effort required to maintain arm elevation, which is particularly beneficial for individuals engaged in continuous keyboard and mouse work.
The goal is to allow the shoulder and neck muscles to remain relaxed in a neutral posture throughout the workday. This is achieved when the support surface is positioned so that the shoulders are neither raised nor slumped. When the upper body is properly supported, the muscles can perform dynamic tasks without the added burden of constant, static weight-bearing. This mechanical relief is the central ergonomic value armrests provide.
Essential Adjustments for Proper Alignment
Armrests only deliver their intended benefits when precisely aligned with the user’s body and workstation. The most important adjustment is the height, which should be set so the shoulders remain relaxed and the elbow is bent at an angle between 90 and 110 degrees. The armrest surface should gently meet the underside of the forearm, providing support without causing the shoulder to shrug upward. Setting the armrests too high forces the shoulders into an elevated, tense position, which negates the entire purpose of load reduction.
Adjusting the width is also necessary to maintain a healthy shoulder position. Armrests must be set close enough to the body so that the upper arms hang vertically and naturally by the sides of the torso. If the armrests are too wide, the user must splay their elbows outward, which can lead to abduction of the shoulder and increase strain on the shoulder joint.
The depth, or length, of the armrest pad is another element that requires attention, particularly in relation to the desk. The armrest should provide sufficient forearm support while still allowing the user to pull the chair close enough to the desk surface. This proximity ensures that the hands can reach the keyboard and mouse without the user having to lean forward or reach excessively.
Common Misuses and Postural Hazards
Despite their potential for support, armrests can quickly become a source of ergonomic risk if not used correctly. One of the most common issues is setting the height too high, which forces the user into an unnatural “shrugged” posture. This constant, low-level elevation of the shoulders leads to chronic tension in the upper trapezius and neck muscles. The resulting muscular imbalance can cause localized pain and contribute to tension headaches over time.
Another significant hazard is contact stress, which occurs when a hard or narrow armrest surface places direct pressure on sensitive areas. Resting the elbow directly on a hard edge can compress the ulnar nerve as it passes through the cubital tunnel at the elbow. This nerve compression can lead to symptoms like numbness, tingling, and weakness in the ring and little fingers. Proper armrests are padded and designed to support the forearm, not the point of the elbow.
Interference with the workspace also creates significant postural problems. Armrests that are too wide or too high may prevent the chair from sliding sufficiently under the desk surface. This obstruction forces the user to sit too far back, which results in leaning forward to reach the keyboard and mouse. Leaning forward pulls the back away from the lumbar support, rounding the spine and negating the chair’s back support features.
Finally, fixed armrests that offer no height, width, or depth adjustment are often counter-ergonomic for general office use. Since the ideal armrest position is highly specific to the user’s body and desk height, a non-adjustable model rarely fits the required neutral posture. In these cases, the fixed armrests can force the user into awkward positions, making it more beneficial to remove the armrests entirely than to use them incorrectly.