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LOAD CARRIAGE OF HEAVY MASSES

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Walking gradient. 10 , 0 , 10. Analysis Tool. Conditions. Postural analysis. 6 Camera System ... H/M COM unloaded walking. L COM closer to unloaded walking ... – PowerPoint PPT presentation

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Title: LOAD CARRIAGE OF HEAVY MASSES


1
LOAD CARRIAGE OF HEAVY MASSES
  • L Mac Duff
  • JR Smith
  • K Smit

2
Objective
  • Report on four of the studies conducted for the
    load carriage research programme
  • Study objectives were to provide specific inputs
    to pack specification on the African Warrior
    soldier pack
  • Address pack design
  • Placement of COM of pack to person
  • Pack design effect on soldier performance and
    user perceptions

3
Background
  • Previous load carriage work from physiological
    perspective
  • Result in upper limit of 35kg mass
  • Required operational items, hydration and food
    often exceeded mass
  • Discussion of pack design for optimal COM
    placement
  • Discussion of frame type
  • OHS

4
Methodology Laboratory studies
5
Insert video clip here
6
Methodology Field study
  • Mobility performance on the STMT and a route
    march, N 30
  • One control, three experimental packs worn over a
    battle jacket
  • Times were recorded for the STMT
  • Perceptual responses for the route march
  • Skin surface pressures- shoulder and hip strap

7
Methodology End user perceptual survey
  • Perceptual survey of pack components
  • N 45
  • Focus groups
  • facilitators
  • translators

8
RESULTSDynamic Postural Analysis
  • Trunk lean angles
  • H/M COM gtunloaded walking
  • L COM closer to unloaded walking
  • Higher the mass the greater the trunk lean angle
  • 50kg80kg had similar trunk lean angles with
    limit of 40º
  • Knee flexion angles lt with gt of mass
  • Postural adjustment to mass COM
  • through knees then trunk, then ankles
  • Stiff legged gait

9
EMG
  • COM placement and gradient had similar trends of
    muscle activity
  • Most stressful of all conditions for back and
    stomach Low COM
  • Least stressful for level gradient Middle COM
  • for incline decline gradient High COM

10
Core stabilizers test
  • Weak correlation with ability to lift loads
  • N 12
  • Does not necessarily confirm protection of soldier

11
Skin surface pressures
  • Self adjusted shoulders gthips
  • Hot spots with square edges
  • Bony aspect of shoulders and hips
  • Shoulder bulk
  • Strap design critical to pressure distribution

12
Perceptual responses
  • Low COM rated consistently highest for all
    conditions
  • High Middle COM rated the same for all
    conditions
  • But..reports of instability with the High COM
  • Strain rating increases with mass increases
  • Body Discomfort
  • 25/35kg shouldersgtbacks
  • 50/80kg Shouldersgtlower legs

13
Placement of COM
  • Optimal placement T4, centred on spine
  • LOW least acceptable
  • High Middle similar, but instability with High.

14
Performance trials
  • Total STMT times not significantly effected by
    pack
  • Balance tasks better with internal frame with
    mass
  • Route march better with external frame
  • Control pack with least acceptable

15
End user perceptual survey
  • Poor use of hip belts
  • Interface with battle jacket and pack critical
  • Preference for external frame
  • Preference for metal not plastic fastenings
  • Requirement for packing volume for water

16
Conclusions
  • Heavy mass is a heavy mass
  • Upper back at T4 between the shoulder blades,
    centered for the COG mass for heavy masses on all
    gradients
  • Pack design is critical to posture, skin surface
    pressure and muscle fatigue
  • User comfort contributes to acceptance of pack
  • Prevalent resistance to using hip belts due to
    quick doffing requirement

17
Recommendations
  • Pack design to facilitate optimal COM
  • Payload mass gt30kg use external frame
  • Strap design interface with battle jacket to
    decrease skin surface pressure
  • Doffing times and use of hip belts, packing
    configurations in doctrine
  • Further investigation into core stabilizing
    protection by conditioning programmes

18
Lorraine Mac DuffE-mail lorraine_at_ergotech.co.za
Website www.ergotech.co.za
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