Postural strain is a common cause of spinal discomfort for many people. ‘Normal’ posture is developed during childhood and young children generally have good postural habits.
A number of factors affect posture - the need to keep the eyes level and facing forward and relative muscle balance around the pelvis and shoulder girdle areas.
When viewed from the side ideal posture (head + pelvis level with neutral tilt) has the ears directly over the shoulder and hip, and a vertical line drawn between them should pass through the knee and reach the ground just in front of the ankles.
When viewed from the back or front, the body should be largely symmetrical. The spine is normally straight but will vary slightly over time with activity and dynamic use. The arms should hang equally and freely on either side.
The curves of the spine should not be excessive but may become so with poor habits.
Poor posture represents a significant risk factor for spinal pain. A number of types of posture are described which have clearly distinguishing features.
Sitting posture is determined by the relative tilt of the pelvis - the degree to which it is tilted back or forwards. When the pelvis is in neutral tilt is considered the best position for good posture.
There are a number of factors which determine this position including seat height, seat depth, seat angle, muscle tightness and weakness etc. The head position + eye level, and the objects being looked at all impact on the seated posture.
If the pelvis rolls backwards into posterior tilt then the lumber spine must flex. This is a stressful position for the tissues, especially the discs and should be avoided for prolonged periods.
Sitting Posture at Work
Work posture may be static or dynamic. Often a mixture of both of these occurs simultaneously as one part of the body does the dynamic work while other areas of the body are held statically in the correct position.
Ideally both the desk and the chair used are adjustable in height. Where this is the case the chair adjustments are made first and then the desk adjusted to the appropriate height for the seated worker. The more common situation is where the desk height is fixed and ergonomic principles are applied to adjust the seated worker to the workstation - in order to make it as safe and effective as possible.
The minimum requirements to maintain good posture are
Feet flat on floor or supported on a footrest IF the height of the seat means the feet are hanging loose off the floor
The knees and hips are flexed at approximately right angles - this means the seat height is at or just above the level of the knees when standing.
The legs should not be crossed
The arms should be hanging relaxed at the sides.
The forearms are just above the level of the desk top + are horizontal with the elbows bent at right angles.
The wrists are in neutral - neither excessively flexed nor extended and not bent sideways. Wide shouldered or bodied people or where the arms are held away from the side may require a split keyboard to maintain a straight on alignment for the hands.
The back should be straight and supported by the backrest. The lumber support of the chair needs to be positioned in the hollow of the lower back and may need the backrest to be adjusted up or down. Avoid slouching!
A slight forward tilt on the seat pan may help encourage upright posture
The shoulders should be over the hips
The arm should not be stretched out in front - especially not with the elbow locked straight. The mouse should be positioned alongside the keyboard
The head should not be forward of the shoulders (protruding chin)
The screen should have the top edge at eye level and be approximately at arms length from the body
Watch out out for the following poor posture
Standing Posture at Work
When work is done standing it is important that the spine is aligned straight wherever possible. Where bending is required it should be kept to the minimum to complete a task and should not be held for prolonged periods of time.
Key factors will include what the hands need to do, where the feet need to be placed,, what surface is being stood on and how stable it is, the head position and eye level / sight lines. The task itself will also determine the correct height at which the workstation is set as precision work requires greater support for the upper limbs while heavy work needs the body weight to be brought to bear during the execution of the task. The following give some indication of what is needed.
Using Laptops, Tablets + Phones
The use of laptops and other mobile digital devices (phones and tablets) may present a risk to health, and must be minimised + avoided if possible.
Many of the same principles apply to the use of portable devices as to using a desktop PC.
Use of portable digital devices over prolonged periods of time is increasingly common.
Safe Usage Guidelines
Portable devices are designed to be used in a wide variety of situations and environments. There are a number of things you can do to maximise safe + effective use.
There id no universally agreed ‘safe’ time limit for using portable devices. Where extended use is required, a suitable desk and chair setup is preferable.
Sustained usage is continuous use for periods of 30-60 minutes.
Extended usage is continuous use for periods of >1 hour.
1 Suitable head, neck and spine postures is a key factor in preventing injury. It is important to maintain good alignment pf the
● Head, Neck + Shoulders,
● Arms + Forearms and
● Wrists + Hands
2. Use a comfortable position / posture. Awkward Postures should be avoided. Sustained or Extended use in an awkward postures is high risk and is not recommended. An awkward posture may include
● Sitting on the floor,
● Sitting cross legged;
● Standing leaning sideways or forwards onto a support (wall / bench)
● Side lying on a floor
● Slouching (back or forwards) whilst seated;
● Resting device on an hand / arm for prolonged periods.
3. It is generally recommended that rest breaks are taken for at least 5 minutes for every 30 minutes of continuous use
4. Regular breaks should be combined with some physical stretches and / or exercises.
5. Eye exercises and visual rest will assist in preventing eye strain (e.g. look at an alternative object several metres away for up to 20 seconds).
6. Maintain a comfortable viewing distance from the screen – approximately 45-70cm.
7. Tilt the screen so that it is at a right angle to the user’s line of sight. Normal line of sight, when the head is upright, is 10' – 15' below the horizontal but can go down as far as 30'. The device screen should ideally be held at 105'-100' to the horizontal but no flatter than 120'
8. Position device so that reflections and glare do not cause a visual disturbance.
Examples of poor posture while using a portable device