Armrests serve a singular purpose within an ergonomic seating arrangement: to support the weight of the user’s upper extremities. This support is intended to reduce the static muscular load on the shoulders and neck, which can become fatigued when forced to hold the arms suspended for long periods. Proper adjustment of these supports is a fundamental part of maintaining a healthy seated posture. When set correctly, armrests allow the shoulder muscles to relax completely, contributing to overall physical comfort throughout the workday. They are a passive tool designed to complement an already good sitting posture, not correct a poor one.
Defining the Ideal Ergonomic Armrest Height
The primary goal of setting the armrest height is to align the body in a neutral, relaxed position that minimizes muscular effort. This position is achieved when the upper arms hang naturally alongside the torso, and the shoulders remain completely down and relaxed, avoiding any upward shrugging or downward slumping motion. The correct height will position the elbow at approximately a 90- to 100-degree angle when the hand is resting near the keyboard. This slight opening of the elbow joint past a right angle promotes a more relaxed posture for the forearm muscles.
The armrest should be adjusted so its pad is just high enough to lightly touch the underside of the elbow and forearm when the shoulder is relaxed. This means the armrest is not pushing the shoulder upward, nor is the arm dangling unsupported. For those working at a desk, the armrest surface should ideally align with or be slightly below the height of the desk surface. This alignment ensures a seamless transition from the chair support to the work surface, helping to keep the wrists straight and parallel to the floor during tasks like typing.
Practical Steps for Setting Armrest Height
Before adjusting the armrests, the user must first establish the correct height of the seat itself, with feet flat on the floor or a footrest and the thighs parallel to the ground. Once seated correctly, the user should sit up straight against the backrest with their shoulders completely relaxed and their upper arms hanging naturally. The next step involves bending the elbow to a 90-degree angle, making sure the forearm is parallel to the ground.
The optimal armrest height is measured from the compressed seat pan to the bottom of the elbow in this 90-degree position. The armrest pad should be raised or lowered until it meets the forearm or elbow at this height, ensuring the shoulder does not elevate. A useful check is to have the armrests just high enough to support the weight of the arms without causing any noticeable lift in the shoulder girdle. If the armrest is adjusted too high, it will force the user’s shoulders to shrug up toward their ears.
A separate consideration involves the relationship between the armrests and the desk. The user must be able to push the chair close enough to the desk so that the keyboard and mouse are easily reachable without leaning forward. If the armrests are too high and collide with the underside of the desk, they must be lowered to allow the chair to slide in. For tasks like typing, some users may find it preferable to lower the armrests slightly below desk height, using the armrests only for resting during breaks.
Health Consequences of Incorrect Armrest Use
Positioning armrests incorrectly can introduce forces that counteract the benefits of an otherwise ergonomic setup, leading to specific musculoskeletal issues. When armrests are set too high, the user is forced to elevate or shrug their shoulders subconsciously to maintain contact. This sustained elevation causes static muscle contraction in the upper trapezius and levator scapulae muscles, leading to chronic tension in the neck and upper back. Over time, this constant strain can manifest as stiffness, headaches, and localized pain in the shoulder and neck region.
Conversely, armrests positioned too low offer inadequate support, leaving the arms to hang unsupported. This lack of support forces the muscles of the shoulder and upper back to work continuously to stabilize the weight of the arms. The resulting fatigue and strain can contribute to shoulder discomfort and an increased risk of disorders like tendinitis. Furthermore, if the arms are unsupported, the user may lean or rest their forearms or wrists directly on the hard edge of the desk, which can compress nerves and soft tissues. This pressure on the underside of the wrist or forearm can increase the risk of developing wrist strain or conditions like carpal tunnel syndrome.