RGM Ergonomics and Sports

What is the definition of ergonomics?

Study of humans, objects, or machines and the interactions among them

What is arthropometrics?

The fit of the human body in the environment

What are the effects of poor ergonomics of the human body?

• Poor muscle control can cause:

  • Joint strain

  • Pain

  • Tissue trauma

• Trauma to tissues can change somatosensory function

  • Mechanoreceptor injury at local site of injury

  • Result can be proprioceptive deficits, altered joint function

• Domino effect (by the time you see pt, there is a lot of things to be fixed)

  • Kinetic chain deterioration (LBP)

What are the components of a work task that a PT evaluates?

• Exerting force

  • Gripping

• Repetition of movements

  • Causing local inflammation from tissue stress

• Posture

  • Static or dynamic

• Motions

  • Bending/twisting

• Compression

  • From tool-holding

• Fatigue

  • Physical/cognitive

• Environmental factors

  • Vibration exposure

  • Extremes of temperature

What effect does exerting force have on the body in terms of ergonomics?

Exerting excessive force can negatively impact the body and cause harm

Explain how too many reps of something can cause stress to the body in terms of ergonomics.

Excessive repetition of movements that can irritate tendons and increase pressure on nerves

Explain how bad postures can cause stress to the body in terms of ergonomics.

Awkward postures, or unsupported positions that stretch physical limits can compress nerves and irritate tendons

Explain how staying in one position too long can cause stress to the body in terms of ergonomics.

Static postures can restrict blood flow and damage muscles

Explain how too much motion can cause stress to the body in terms of ergonomics.

Motion, such as increased speed or acceleration when bending and twisting can increase the amount of force exerted on the body

Explain how too much hand compression can cause stress to the body in terms of ergonomics.

Compression, from grasping sharp edges like tool handles, can concentrate force on small areas of the body, reduce blood flow and nerve transmission, and damage tendons and tendon sheaths.

Explain how not enough rest can cause stress to the body in terms of ergonomics.

Can leave insufficient time for tissue repair

Explain how vibration can cause stress to the body in terms of ergonomics.

Can decrease blood flow, damage nerves, and contribute to muscle fatigue.

Whole-body vibration (driving trucks or operating subways) can affect skeletal muscles and cause LBP.

Explain how temperature can cause stress to the body in terms of ergonomics.

Cold temps can adversely affect a worker’s coordination and manual dexterity and cause a worker to use more force than necessary to perform a task

What are things that occur in the spine as a result of poor posture tendencies?

• Increased lumbar lordosis

• Increased thoracic kyphosis

What are things that occur in the lumbopelvic region as a result of poor posture tendencies?

• Decreased hip extension

• Decreased M-L stability

• Increased hip flexion alignment

What are things that occur in gait as a result of poor posture tendencies?

• Decreased A-P stability

• Decreased stride length

• Greater weight placed on the forefoot

• Increased double-foot stance time

• Harder heel strike

As poor postural tendencies occur, neuromuscular decline continues. What does this cause?

Locomotor system becomes less able to adapt to environment.

Requires greater attention to recruit more sensory information to keep postural control

What compensations in gait occur as a result of neuromuscular decline due to poor posture tendencies?

• Broadened stance to combat increased M-L instability

• Shortened stride length to maintain COG

What compensations in the UEs occur as a result of neuromuscular decline due to poor posture tendencies?

• Decreased integration of upper body counter-rotation

• Increased visual sensory input

• Recruitment of additional input for postural equilibrium

What are basic ways to correct a work environment for improved ergonomics?

• Set up workstation to keep everything within easy reach so that joints function in neutral positions and neutral postures can be maintained.

• Maintain adequate clearance around workstation for safe environment

• Use adequate lighting

What are basic ways to correct a work tasks for improved ergonomics?

• Minimize excessive repetitive motions

• Reduce excessive forces

• Minimize need to maintain a static hold on objects or maintain a static posture leading to fatigue.

• Minimize pressure points

• Move head, spine, and extremities through their ROM frequently

How is stability of the GHJ achieved?

• Active mechanisms

  • Muscles of rotator cuff

    • Must work dynamically. Requires healthy somatosensory systems to work

• Passive mechanisms

  • Tension of capsule, ligaments, labrum, tendons

• Negative intracapsular pressure

  • Again, via alignment and tone

• All are manifestations of postural control elements

  • Tone at rest

  • Muscle strength/power

  • Alignment

  • Available ROM

How is scapulohumeral rhythm achieved? 

• For every 3 degrees of abduction,

  • 2 degrees is from GH abduction

  • 1 degree is from scapulo-thoracic (ST) upward rotation

• So, in 180 degrees of abduction,

  • 120 is from GH abduction

  • 60 is from ST upward rotation

What is a force couple?

Forces which are equal in magnitude, parallel and opposite in direction

What motions are combined to permit overhead motion of the arm?

Scapular elevation and scapular upward rotation

What is the minimum amount of shoulder abduction/flexion a person needs to perform ADLs?

Typically at least 130 degrees of shoulder flexion/abduction.

(Dr. G says 140 degrees [PURP HEX])

What is scapular dyskinesia?

Any abnormal position or movement of the scapula

What are the most common findings of scapular dyskinesia?

• Reduced upward rotation

• Excessive downward rotation, IR, anterior tilt, or elevation

What is the sequencing of overhead throwing?

Lower limbs → trunk → arm → hand

Each limb initially lags behind the next in order. Then accelerates to even higher speeds while the preceding segment now lags behind

Describe the role of ER and IR in healthy overhead throwing. Why does ER need to increase?

• Increased passive range of ER reduced passive IR.

• Speculation that the loss of IR and the gain of ER is needed for healthy throwing.

To achieve a curveball, what does a pitcher need regarding their hands?

• Pitcher imparts spin on the ball.

• The order of finger release on the ball matters.

• Pattern of release varies

  • 75%: thumb → middle finger → index

  • 25%: middle → thumb → index

For throwing athletes, what are aspects of volume and force that you may need to know?

• Consider the throwing volume and distance a player must perform 

• Note that most throws are shorter distances 

• Some positions throw more or further as part of their role 

In the Laudner 2012 study, why did football players have worse shoulder stability than recreational athletes?

Because the football players had shoulder instability due to repeated microtrauma (throwing and tackling), which diminished control.

What are two non-modifiable risk factors for injury in overhead athletes?

• Playing position

• Gender

  • Women use techniques that demand more rotational strength.

What are three modifiable risk factors for injury in overhead athletes?

• Shoulder rotational strength

  • Lack creates greater risk in women (women should strengthen rotation strength)

• Scapular dyskinesia

  • Presence creates greater risk in men

• Presence of shoulder injury prevention programs

  • Decreases risk for minor injuries

  • Consists of 10 min warm-up. Does not decrease risk for moderate-severe injuries