Repetitive Strain Injury

Improper work habits, poor workstation ergonomics, and environment can lead to physiological dysregulation such as muscle soreness, fatigue, and injury (Grandjean, 1987). Some workers develop chronic neck and upper limb pain also known as repetitive strain injury. (RSI), cumulative trauma disorder (CTD) or overuse syndrome, from long hours of repetitive tasks at personal computer workstations. Workers with RSI suffer loss of productivity and income with increasing medical costs. RSI accounted for forty percent of workers compensation cases in 1990. Discomfort and injury can shape the way PC users feel about their job and computers. Forty million Americans use computers, and 15-20 percent are at risk for RSI symptoms (CDC, 1984). RSI threatens to inflict individuals with illness and overwhelm corporations with increasing medical costs and lost productivity.

At present, workstation ergonomic analysis, proper positioning of furniture and equipment, different mice and keyboards, and periodic rest may help reduce physiological dysregulation (the incidence of muscle fatigue or injury). This mechanical approach, however, lacks two crucial elements:

The computer user must learn to reduce tension and relax muscles when they are not used for the task. Preventing RSI involves a combination of proper ergonomics, work pattern variation (work/rest cycle), and self-regulation through biofeedback to reduce dysponetic activity (inappropriate and misdirected, as well as unconscious muscle bracing). Without kinesthetic awareness and without the skills to reduce tension, ergonomic adjustments with intermittent rest periods are NOT sufficient to reduce risk for injury.

Computer users can learn preventative skills to sense muscle tension and incorporate relaxation and regeneration of muscles during data entry and mouse use. Biofeedback instruments can be used to monitor specific muscle sites and to warn the user of excessive strain or overuse habits that can lead to chronic pain or injury. This mastery process reduces the risk of RSI.

The development of RSI involves ergonomic and psychophysiological contributing factors which include:

The following RSI protocol includes ergonomic and work style evaluation, psychophysiological profile, risk factor analysis, biofeedback training and education.

Ergonomic evaluation needs to be done at the work site under normal working conditions. (Compare the computer user position to the recommended guidelines, see Fig. 1.) The attached assessment form, SFSU WORKSTATION AND ERGONOMIC ASSESSMENT (Peper and Tibbetts, 1994) can be used as a guideline to cover most of the ergonomic risks (see also Jones, 1991; State of California, 1993). At the same time, movement analysis of task performance needs to be included because repeated asymmetrical movements increase risks (Donaldson, 1994). A table of typical computer user complaints, corresponding ergonomic factors, and areas for surface electromyography (sEMG) are listed in Table 1 (Wilson, 1994).

Figure 1. Workstation arrangement to reduce risk of discomfort. (Illustration, courtesy of Great Performance, Inc. (800)433-3803).

After evaluation, ergonomic risks are identified and solutions proposed. Many solutions can be economical, such as lowering the monitor by placing the computer sideways on the floor, lowering the keyboard by attaching a keyboard drawer, raising the feet by using telephone books, and removing boxes or waste basket from under the desk so that the legs are free to move. Sometimes, the solution requires a reorganization of the office, such as moving office furniture, to reduce excessive reaching, or to allow distant vision.

In cases of asymmetrical job patterns, the person is guided to do the job alternately using opposite sides of the body, as well as changing the position of furniture (phones, files) to balance movement patterns. For example, during the morning, place the phone on the left side and lift the receiver with the left hand, while during the afternoon, place the phone on the right side and use the right hand.

An additional factor commonly overlooked is appropriate vision correction, especially for people who wear bifocals. Prescribed reading glasses (often used at the computer) force the user to tilt the head back or hunch forward since the focal distance is not set at the distance of their workstation monitor (Grandjean 1987). Some users may need to have special computer monitor reading glasses.

Equally important, computer users need to be aware of the work/rest cycle. This means both very short breaks and movements during task performance and larger body movements during frequent longer breaks.

After ergonomic assessment and adjustments, a physiological assessment should be done. If possible, it should include an actual work site assessment, which can easily be done with a laptop computer and a portable two channel EMG device like Thought Technology's MyoTrac2(TM) or ProComp+(TM) systems. The comprehensive profile consists of different phases which can also be selectively used depending upon the computer user's needs.

The psychophysiological profile consists of physiological monitoring during: a) task performance, b) simulated emotional stress, c) extended data entry, and d) movement symmetry. The purpose is to assess dysponetic activity (misdirected and inappropriate bracing patterns), the length of short breaks, the effect of emotional stress upon physiological reactivity, physiological recovery, asymmetrical muscle co-contractions, and somatic awareness.

The profile assesses the individual at the computer, either at the job site or at a simulation of the workplace setting. The data entry task needs to include the actual data entry pattern of the user (e.g. keyboard, mouse, and/or trackball). The initial assessment does not include feedback, although all the data is recorded for later analysis.

IMPORTANT: The protocol should be adapted to assess real task performance such as job related data entry, reaching for the phone with the right and left hand, etc.

After the protocol has been completed, the data can then be reviewed with the client to show the individual's physiological responses. This information is then used to determine self-regulation strategies to improve health. This feedback is usually done directly after the assessment so that the information can be used to begin retraining.

The minimum requirement for the assessment is two channels of surface electromyography (sEMG). A two channel sEMG assessment will require moving sensor leads to different muscle sites during different phases of the assessment. A more comprehensive assessment would include a minimum of 4 channels of sEMG, respiration, skin temperature (Temp) and skin conductance response (SCR).

Two channel sEMG sensor placement:

A) Forearm sEMG: Place the active electrodes midpoint on the extensor and flexor muscles (see Fig. 2) to monitor forearm tension. The purpose for monitoring the forearm is that most subjects do not relax the fingers or wrist muscles as long as the fingers are on the keyboard or holding the mouse.

B) Neck and shoulders sEMG: Place one active electrode over the left scalene and the other, midpoint on the right trapezius (see Fig. 3). The purpose of monitoring the neck and shoulders is that most subjects raise their shoulders and tend toward thoracic breathing patterns during task performance. The left scalene to right trapezius placement will also monitor bracing by the scalene and sternocleidomastoid muscles.

Four channel sEMG sensor placement:

Sensors are placed to allow bilateral analysis during the symmetry assessment. The most common bilateral electrode placements (right and left) include the following muscles: upper trapezius, lower trapezius, sternocleidomastoid, rhomboid, and pectoralis. The purpose for monitoring upper and lower trapezius is to enhance scapular stabilization since the lower trapezius will inhibit the upper trapezius activity. (For exact electrode locations see: Soderberg, 1992: This manual is free and available from NIOSH, see recommended sources for more information; and Basmajian & Blumenstein, 1980).

Comprehensive monitoring includes thoracic and abdominal respiratory patterns and breathing rate, peripheral temperature, skin conductance, and heart rate. Monitoring should also include the following sEMG placements, bilateral cervical paraspinals, masseters, temporalis, deltoid, upper and lower trapezius, pectoralis, infraspinatis, wrist extensors and flexors, and possibly, tibialis and gastrocnemius.

PURPOSE:
To assess subjective muscle tension awareness, posture and task performance upon the physiology.

RISK PATTERNS:
The following are common physiological patterns which may be identified and may increase risk (Fig. 4).

Figure 4. Common Dysfunctional Physiological Patterns include: Increased scalene/trapezius sEMG activity when the hands are on the keyboard and during typing. Increased forearm flexor/extensor sEMG activity when the hands are on the keyboard. Absence of micro-breaks (low sEMG epochs) when typing. Increased respiration rate when the hands are on the keyboard and when typing. Decreased abdominal expansion while breathing when hands are on the keyboard and when typing.

RISK PATTERNS:
The following are common risk patterns, in addition to those described in PHASE 1, which need to be retrained (Fig. 5).

Figure 5. The effect of stressful imagery on right upper trapezius muscle activity. Note that there are NO micro-breaks during the typing with stressful imagery, while there are micro-breaks (epochs of low EMG) during the normal typing task. In addition, the EMG activity is significantly increased during stressful imagery in both the sitting, arms in lap, and the typing conditions.

RISK PATTERNS:
The following are common risk patterns, in addition to those described in PHASE 1 and 2, which need to be retrained.

PHASE 4:
Symmetrical Movement Analysis for Muscle Co-Contraction and Recovery Analysis

PURPOSE:
To assess sEMG imbalance during movement patterns (Taylor, 1993; Wilson, 1994; and Skubick, Clasby, Donaldson, & Marshall, 1993; Donaldson, 1994).

PROCEDURE For SCM sEMG assessment:
SENSOR PLACEMENTS:
Use two or four EMG channels, place sEMG active sensors on the right and left sternocleidomastoid (SCM) (optional: right and left upper trapezius)(Fig. 3).

ALTERNATIVE MOVEMENT PATTERN:
Have person perform real job tasks such as reaching for the phone, manuals, or turning pages with one hand and then with the other hand. Repeat movement 5 times.

PROCEDURE For upper trapezius assessment:
SENSOR PLACEMENTS:
Use two or four EMG channels, place sEMG sensors on right and left upper trapezius (optional: right and left SCM).

ALTERNATIVE MOVEMENT PATTERN:
Have person perform movements which mimic common job movements.

OPTIONAL:
Repeat one cycle of the above movement patterns while changing the time duration 30-60 seconds at the full extension. (Do not continue if pain occurs.) Allow at least 120 seconds for recovery between right and left movements.

RISK PATTERNS:
The following are common risk patterns, in addition to those described in PHASE 1, 2, and 3, which need to be retrained.

Review the recorded data from the assessment protocol. Identify physiological response patterns and work habits which may increase the risk of RSI. The most commonly observed risk patterns are the absence of muscle tension awareness (awareness of muscle tension does not correlate with sEMG activity), inability to relax muscles, dysponesis (bracing of the trapezius during data entry), increased arousal during data entry, absence of regenerative micro-breaks during typing tasks (see Figs. 4 and 5), asymmetry and co-contractions during movement, and absence of gross body movement patterns.

The training protocol consists of reducing the observed risk patterns and generalizing these new skills into the persons work behavior. If significant dysponesis is observed, a more detailed sEMG analysis of specific muscles is required. The more specific the feedback, the more successful will be the skill acquisition.

The general training themes consist of increasing awareness of dysponetic activity, inhibiting co-contraction by tightening the correct agonist and inhibiting the antagonist, encouraging regenerative micro-epochs of very low sEMG activity of an activated muscle, reducing arousal (startle) during data entry through methods such as continued breathing, developing movement patterns using both sides of the body equally, and teaching that health consists of the alternation between activity and regeneration (movement and relaxation). The training goals are enhanced when monitored with portable EMG trainers (MyoTrac and MyoTrac2) or computer based systems (ProComp, FlexComp or MyoTrac2). The general psychophysiological concepts to achieve training goals are:

CAUTION: Any numbness, tingling, prickling sensation or loss of sensation or dropping of objects should be evaluated by a physician. These symptoms are most prevalent in the early morning, evening or wakes the person from sleep.

Figure 6. The use of sEMG from right trapezius, deltoid, and forearm to optimize keyboard location. Position 1 is resting with hands on lap, position 2 is most ergonomically correct with hands at keyboard, while position 3, 4, and 5 are ergonimacally incorrect. NOTE that there is NO correlation between sEMG activity and subjective awareness of tension as indicated by the numerical scores (1 - most relaxed to 5 - most tense) for each position and shoulder and forearm body locations.

Every person who uses or begins to use a computer should be instructed in somatic awareness, proper ergonomics, and rest/activity cycles. For many people, a signal from a small portable sEMG feedback device can help facilitate awareness of dysponesis during data entry and mouse use. Both the MyoTrac and MyoTrac2 devices (from Thought Technology Ltd.), offer the option for delayed tone feedback. This delayed feedback ignores the normal stretching, yawning, and other brief movements, whereas sustained sEMG activity triggers a warning feedback tone. In addition, external reminders to trigger brief regenerative breaks, as well as, encouraging episodic body movements may reduce the risk of RSI (e.g., timed alarms or automatic data entry interrupts). Finally, this protocol can be used to teach computer users preventative skills to avoid RSI and mobilize health. Table 1:

TYPICAL COMPUTER USER COMPLAINTS, CORRESPONDING ERGONOMIC FACTORS AND SUGGESTED MUSCLE GROUPS FOR SENSOR PLACEMENT

HEAD
Typical complaints	Possible ergonomic factors	Areas of sEMG placement
Eye strain: Pain or fatigue	VDT distance and tilt Lighting Optical prescription	Frontalis/posterior neck Temporalis Suboccipital Frontal
Headache	Telephone usage Rest breaks from VDT Sitting posture Squinting Clenching teeth Fumes of toner Fluorescent lights	Frontal/posterior neck Temporalis Masseter Suboccipital Cervical paraspinal Trapezius Sternocleidomastoid
NECK AND SHOULDERS
Typical complaints	Possible ergonomic factors	Areas of sEMG placement
Headache back of head or neck	Document position (flat) Distance from VDT (too far) Head off-center Arms not supported Bifocals	Frontal/posterior neck Trapezius Masseter Sternocleidomastoid
Pain in shoulders	Head tilt (display too high or too low Bifocal glasses Hunched shoulders (keyboard height too high) Drooped shoulders (too far away from keyboard. no muscle tone) Mouse distance One-sided movements	Trapezius Deltoid Pectoralis Infraspinatus Scalenes
ARMS, WRISTS AND FINGERS
Typical complaints	Possible ergonomic factors	Areas of sEMG placement
Elbow pain	Repetitive motion/no rest Keyboard design Mouse distance	Triceps Brachioradialis Forearm extensors Scalenes
Wrist pain	Repetitive motion/no rest	Upper shoulder Sternocleidomastoid Brachioradialis Forearm extensors Scalenes
Finger pain	Repetitive motion/no rest	Digital Extensors Forearm extensors Scalenes
BACK
Typical complaints	Possible ergonomic factors	Areas of sEMG placement
Lower back or hip pain	Chair (lumbar support) Posture Leg Position Feet on floor (sloped rest) High/low hip or shoulders Hip beneath knee	Upper back Lumbar region
LEGS, ANKLES AND FEET
Typical complaints	Possible ergonomic factors	Areas of sEMG placement
Elbow pain	Repetitive motion/no rest Keyboard design Mouse distance	Triceps Brachioradialis Forearm extensors Scalenes
Wrist pain	Repetitive motion/no rest	Upper shoulder Sternocleidomastoid Brachioradialis Forearm extensors Scalenes
Finger pain	Repetitive motion/no rest	Digital Extensors Forearm extensors Scalenes
BACK
Typical complaints	Possible ergonomic factors	Areas of sEMG placement
Lower back or hip pain	Chair (lumbar support) Posture Leg Position Feet on floor (sloped rest) High/low hip or shoulders Hip beneath knee	Upper back Lumbar region
LEGS, ANKLES AND FEET
Typical complaints	Possible ergonomic factors	Areas of sEMG placement
Pain down the leg	Compression from chair (inadequate padding on bottom, sharp front edge) Leg position (crossed legs or sharp leg bend One side movement	Hamstrings Glutei Piriformis
Swollen ankles	Lack of movement
Pain in foot or toes	Feet not on floor/sloped rest Poor circulation Leg position Lack of movement

SFSU WORKSTATION AND ERGONOMIC ASSESSMENT
(Peper & Tibbets, 1994)

Instructions: Observe and circle possible risk factors.

Name: ____________________ Date: _____________ Rater: ____________________

Monitor     80 degrees from eye position      High ___   Low ___
              Distance 3 feet                          Near ___   Far ___   ? ___
              Position                                    Left ___ Right ___   ? ___
              Glare and reflexion                      Yes ___     ? ___
              Bright lights                              Yes ___     ? ___
              Needs larger screen                  Yes ___     ? ___
              High.clear screen resolution       No   ___     ? ___
              Ability to look at a far object       No   ___     ? ___
              Glasses-bifocals                       Yes ___     ? ___
              Contacts                                  Yes ___     ? ___
              Uses reading/computer glasses    Yes ___     ? ___
              Position of reading material      Near ___ Far   ___
                                                             High ___ Low   ___

Comments:________________________________________________________________

Chair        Feet reach floor                          No   ___     ? ___
              Thighs compressed                    Yes ___     ? ___
              Seat angles back                       Yes ___     ? ___
              Back support                             No   ___
              If present, is it used?                  No   ___     ? ___
                                                              High ___   Low ___
              Arm rests                                  Yes ___
              Lifts shoulders                           Yes ___     ? ___

Comments:________________________________________________________________

Legs         Enough room for feet                  No   ___     ? ___
              Space for leg movement            No   ___     ? ___
              Angle of knees at 110^o                No   ___     ? ___
              Foot support                               No   ___     ? ___
              If present, is it used                    Yes ___    No ___
                                                               Sometimes     ___

Comments:________________________________________________________________

Keyboard   Adjustable                     No   ___     ? ___
                                                   High ___   Low ___
               Stable                           No   ___     ? ___
               Wrist pad                      No   ___     ? ___
                                                 Hard ___     ? ___

Comments: _____________________________________________________________

Arms      Angle of upper arm (vertical)     Forward ___ Backward ___
              Angle of forearm at elbow (110^o) Smaller ___ Greater ___
              Elbows out                               Yes ___        ? ___
              Angle of hand                            Flexed ___ Extended ___
              Finger nails                               Long ___        ? ___
              Types with finger nails               Yes ___        ? ___
              Tension visible (tendons, fingers)    Yes ___        ? ___

Comments: _____________________________________________________________

Mouse/        Present                           Yes ___        ? ___
trackball       Frequency of use              Often ___ Sometimes___
                   Location                      Distant ___        ? ___
                   Reaches out to side           Yes ___        ? ___
                   Reaches out forward           Yes ___        ? ___

Comments: _____________________________________________________________

Phone         Frequency of use                    Often ___ Sometimes___
                  Duration of use                        ___ Minutes
                  Twists for use                         Yes ___        ? ___
                  Location                                 Distant ___
                  Shoulder rest                            No ___        ? ___
                  Headset                                  No ___        ? ___
                  Writing.data entry during calls   Yes ___        ? ___

Comments: ___________________________________________________________

Space         Enough room on desk                No ___        ? ___
                  Office space personalized           No ___        ? ___
                  Back to door                              Yes ___      ? ___

Comments: _____________________________________________________________

Work habits   Takes breaks every 15-30 min.            No ___       ? ___
                     Does multiple body movements/task   No ___       ? ___
                     Assymetrical movements during task Yes ___      ? ___
                     Reaching during work                       Yes ___      ? ___
                     Mini-breaks during keyboard entry       No ___        ? ___
                     Percent time at computer                 <25% 50% 75%> ? ___
                     Previous workstation assessment
                     and/or suggestions implemented?        No ___        ? ___

Comments: ____________________________________________________________

Personal      Clothing                                         tight ___      ? ___
                   Belt (waist constricted)                   Yes ___      ? ___
                   Stationary (abscence of movement)   Yes ___      ? ___
                   Thoracic breath pattern                    Yes ___      ? ___
                   Shifts to thoracic breath
                   pattern while working                       Yes ___      ? ___
                   Skewed posture while sitting              Yes ___      ? ___
                   Startle posture                                 Yes ___      ? ___
                   Conscientious/driven                        Yes ___      ? ___
                   Hands                                           Cold ___ Moist ___      ? ___
                   Smoking                                        Yes ___      ? ___

Comments: ___________________________________________________________

Workstation adjustment suggested: ________________________________________

__________________________________________________________________________

__________________________________________________________________________

__________________________________________________________________________

Changes in work habits suggested: _______________________________________

__________________________________________________________________________

__________________________________________________________________________

__________________________________________________________________________

Psychophysiological profile appointment date: _________________________________

Two channel sEMG sensor placement:

Four channel sEMG sensor placement:

SFSU WORKSTATION AND ERGONOMIC ASSESSMENT (Peper & Tibbets, 1994)

Instructions: Observe and circle possible risk factors.

Footnotes:

SFSU WORKSTATION AND ERGONOMIC ASSESSMENT
(Peper & Tibbets, 1994)