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Aspire 2024 Title Page

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Neuromuscular and movement control strategies with soft passive low back exoskeleton use during EMS-specific physical agility tests

Tiash Rana Mukherjee*, Tiago Gunter, Eshan Manchanda, Oshin Tyagi, Ranjana K. Mehta

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Motivation

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2 million Emergency Medical Technicians and Paramedics help 22 million patients each year1

22,781 injuries in Emergency Medical Service2

Injury rate – 3 times the national average across any occupation2

1. NIOSH (2022) ,2. Kim et al (2017)

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Motivation

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Main cause: Patient Handling and Lifting ​

42% injuries lower back 1,2​

1. NIOSH (2022) ,2. Kim et al (2017)

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Current Mitigation Strategies

3. Cole (2018) 4. Crill et al (2005) ​

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  • Injury rates are still high ​
  • Thus, current solutions and techniques are not very effective ​

Current Mitigation Strategies

3. Cole (2018) 4. Crill et al (2005) ​

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Unpredictable Environments4

Strenuous Physical & Cognitive Demands 4,5

    • Lifting over recommended limits
    • Time Pressure
    • Rapid Response

Limitations to design solutions

4. Sayre, MR, et al (2002) 5. Horberg, A. et al (2019)

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Potential Solution

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Can soft passive low back exoskeletons help?

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  • Reduced muscle activity in the lower back 6,7,8,9
  • Relatively better than hard low back exoskeletons7,8,9
    • Less Restrictive 🡪 More Flexibility
    • Light Weight 🡪 Easy to Wear
  • Greater Adaptability to different work requirements6,8

6. Goršič  et al (2021) 7. Yandell et. al (2020) 8. Novak et. Al (2023) 9. Nuesslin et al (2023)

Potential Benefits?

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Research Gap

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Despite evaluations in other settings, the efficacy of soft low back exoskeletons in highly dynamic & unstructured environments such as Emergency Medical Service environments remains unexplored!

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Evaluate the effects of using a soft passive low back exoskeleton during simulated emergency medical service tasks

Research Aim

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Focus on:

  1. Neuromuscular Effects
  2. Postural Effects
  3. Performance
  4. Perception

Research Aim

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  • Reduced Muscular Load in the lower back
  • Altered functional range of motion.
  • EMT-Ps would perceive reduced physical and mental demands

Hypotheses

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Methodology

  • Intended Users
    • 20 EMTs (10% F)
    • Between Subject Design
    • Controlled Field Investigation
    • Critical Tasks Evaluated
  • Demographics (Average (SD))
    • Age: 33.1 (8.2) years
    • Height: 176.2 (8.3) cm
    • Weight: 98.2 (14.2) kg
    • Experience: 10.1 (8.3) years
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Modified Physical Agility Test

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Tasks Performed

Pulling the stretcher out from a parked ambulance until it automatically unloads and loads it back

Performing CPR on a dummy for 120 seconds

Carrying a 20lb cardiac monitor with the right hand across a staircase

One-hand

Carry

Squat Lifting and holding a 150 lb. dummy for 5 seconds

Backboard

Lift

Carrying a 75lb barbell at shoulder level across a staircase

Barbell

Carry

Stretcher Push/Pull

Cardiopulmonary Resuscitation (CPR)

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Experimental Settings

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Subjective Measurements

  • Between Tasks
    • Ratings of perceived exertion
    • Ratings of mental demand
  • Between Conditions
    • NASA - Work Load Index

​

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Performance

  • Task Completion Time
  • #Compressions During CPR
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Electromyographic Measurements

Muscle activity collected bilaterally from:

​

    • Shoulder
      • Anterior Deltoid
      • Upper Trapezius
    • Back
      • Lumbar Erector Spinae
    • Lower Limbs
      • Biceps Femoris

​

Reference Task: Stoop Lifting 20 lbs cardiac monitor

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Joint Kinematics

Functional Range of Motion Calculated as:

Joint Angle =

(95th Percentile – 5th Percentile) ​

​

  • Head ​
  • Shoulder​
  • Elbow ​
  • Wrist ​

​

  • L5/S1​
  • Hip ​
  • Knee​
  • Ankle ​

​

​

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Results

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Performance

Seconds (s)

Task Completion Time & #Compressions

​

Comparable between conditions

​

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Task 1: Backboard Lift

Average Muscle Activity

  • 15% RVC ↑ in mean left biceps femoris activity

​

Functional Range of Motion

  • No differences observed in joint kinematics

​

9. Yoo et. al (2012

Exoskeleton use potentially helped with redistribution of load aiding lower limbs stability9

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Mean Muscle Activity

  • Reduction in mean bicep femoris activity

​

​

Functional Range of Motion

  • ~15°↑ in mean hip adduction ROM

​

10. Tanaka et. al (1984)

%RVC

Task 2: One-hand Carry

LBE engagement with hip adductors, aided limb support and load redistribution10

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Average Muscle Activity

  • 40% RVC ↓ and 30% RVC ↑ in mean right and left bicep femoris activity, respectively
  • 20% RVC ↓ in the right upper trapezius

​

Functional ROM

  • ~10° in mean knee rotation
  • ~4° in mean ankle flexion

​

​

​

11. Lyon et. al (1983) ​

Weight transfer to non-dominant leg with reduced knee rotation and increased ankle flexion to aid stability11

Task 3: Barbell Carry

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Mean Muscle Activity

  • Reduction in right and left erector spinae

​

Functional Range of Motion

  • No differences joint kinematics

​

Exoskeleton use helped reduced lower back demands

Task 4: Stretcher Push/Pull

%RVC

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Mean Muscle Activity

  • Reduction in bicep femoris activity

​

Functional Range of Motion

  • 6° knee rotation and 3° adduction

​

13.Ho et. al (2018) ​

Reduced ROM aided upright position during kneeling, aiding upper body weight application during compressions13

Task 5: Cardiopulmonary Resuscitation (CPR)

%RVC

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Key Results from Objective Analysis

  • Benefits primarily observed in lower limbs and during specific tasks (e.g., CPR, carrying)

​

  • Lower back muscular demands reduced for tasks involving stretcher push/pull out of ambulance

​

  • Functional Range of Motion was not affected for less dynamic tasks

​

  • Task Completion Time not affected

​

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Subjective Responses during Tasks

Comparable between conditions for all tasks!

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But Subjective Responses after circuit?

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Physical Demands, Temporal Demands and Effort reduced with Exoskeleton use !

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Mismatch between perception of physical and mental effort during & after tasks?�

  • Tasks were of smaller durations?13
  • EMTs getting used to exoskeleton use?
  • Individual Variability?
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13. Dallaway et. Al (2022)

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Limitations & Future Work

  •   Immediate benefits not recognized is a concern 1​4
    • This can affect user’s willingness to adopt LBEs​
    • Need to investigate user perception and perspectives​

​

14. Mun et. al (2006) 15. Bennet et. al (2023) 16. Gorsic et. al (2021) 4. Bennet (2022) 17. Ojelade et. al (2023) 18. Kim et. al (2024) ​

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  • Sex differences might influence HEI  15-16
    • Studies evaluating LBEs have reported significant sex differences  ​
    • Particularly due to sex-based differences in human physiology ​

​

  • Current study focused only on Range of Motion and Muscle Activity 16-18​
    • What happens during the task?
    • Is the LBE use enhancing task performance? ​
    • Did EMTs adopt different postural strategies to accommodate similar levels of performance?​

​

​

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Research to Practice!

This research supports that soft passive low back exoskeletons have the potential to aid emergency medical technicians!

​

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Thank you!

Tiash Rana Mukherjee

Work supported under NSF Grant 2033592

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