Select SLIDE MASTER to Insert Briefing Title Here
Heavy external loads disproportionately
increase walking energy expenditure
David P. Looney PhD CSCS
Adam W. Potter MS
Holly L. McClung MS
Alexander P. Welles MS
William R. Santee PhD
Biophysics and Biomedical Modeling Division
US Army Research Institute of Environmental Medicine (USARIEM)
Natick, MA 01760
DISCLAIMER. The opinions or assertions contained herein are the private views of the authors and are not to be construed as official or as
reflecting the views of the Army or the Department of Defense. Citations of commercial organizations and trade names in this report do not
constitute an official Department of the Army endorsement or approval of the products or services of these organizations
Name/Office
Symbol/(703)
XXX-XXX
(DSN XXX) / email
address
Dave Looney
PhD, Research
Physiologist
/ david.p.looney4.civ@mail.mil
/ (508) 233-5027
Slide 1
25-Oct-18
7/14/2018
Select SLIDE MASTER to Insert Briefing Title Here
Total Mass & Energy Expenditure
Does an 85-kg man expend as much energy when walking
as a 50-kg man carrying a 35-kg load?
85
Name/Office
Symbol/(703)
XXX-XXX
(DSN XXX) / email
address
Dave Looney
PhD, Research
Physiologist
/ david.p.looney4.civ@mail.mil
50
/ (508) 233-5027
35
Slide 2
25-Oct-18
7/14/2018
Select SLIDE MASTER to Insert Briefing Title Here
Introduction – Load Carriage
• Dismounted military operation planning involves weighing advantages of
extra equipment against metabolic costs
• Existing predictive models underestimate energy expended during heavy
military load carriage (Drain et al. 2017, Looney et al. 2018)
Photograph: Army Times
From https://www.armytimes.com/news/2017/11/08/researchers-study-how-much-energy-troops-burn-while-walking-carrying-loads/
Name/Office
Symbol/(703)
XXX-XXX
(DSN XXX) / email
address
Dave Looney
PhD, Research
Physiologist
/ david.p.looney4.civ@mail.mil
/ (508) 233-5027
Slide 3
25-Oct-18
7/14/2018
Select SLIDE MASTER to Insert Briefing Title Here
Introduction – Load Effects
• Heavier loads increase energy
expenditure to a greater extent
(Pandolf et al. 1977)
• Loads < 20% body mass do not
increase energy expenditure
(Charteris et al. 1989)
• Energy expenditure increases linearly
with load carried (Bastien et al. 2005,
Ludlow et al. 2017)
• Does energy expenditure increase
proportionally with load?
Photograph: Courtesy of Wikipedia.org.
From https://peosoldier.army.mil/factsheets/SEQ_ CIE_MOLLE.pdf.
Name/Office
Symbol/(703)
XXX-XXX
(DSN XXX) / email
address
Dave Looney
PhD, Research
Physiologist
/ david.p.looney4.civ@mail.mil
/ (508) 233-5027
Slide 4
25-Oct-18
7/14/2018
Select SLIDE MASTER to Insert Briefing Title Here
Introduction – Scenario
Does an 85-kg man expend as much energy when walking
as a 50-kg man carrying a 35-kg load?
85
50
35
3.6 W∙kg−1 × 85 kg
3.6 W∙kg−1 × 50 kg + 35 kg
306 W
306 W
Name/Office
Symbol/(703)
XXX-XXX
(DSN XXX) / email
address
Dave Looney
PhD, Research
Physiologist
/ david.p.looney4.civ@mail.mil
/ (508) 233-5027
Slide 5
25-Oct-18
7/14/2018
Select SLIDE MASTER to Insert Briefing Title Here
Purpose
• Purpose
– Determine if walking energy expenditure (EE) increases proportionally
with added loads
• Design
– Systematic Review
– Meta-Regression
Name/Office
Symbol/(703)
XXX-XXX
(DSN XXX) / email
address
Dave Looney
PhD, Research
Physiologist
/ david.p.looney4.civ@mail.mil
/ (508) 233-5027
Slide 6
25-Oct-18
7/14/2018
Select SLIDE MASTER to Insert Briefing Title Here
Methods – Literature Search
• Searched literature for studies that measured energy expenditure during
loaded walking in healthy, military-age men & women
• Search terms included:
–
–
–
–
“Load carriage” OR “Walking”
“Backpack” OR “Load” OR “Resistance” OR “Weighted”
“Energy” OR “Metabolic” OR “Oxygen”
“Cost” OR “Economy” OR “Expenditure” OR “Rate”
Name/Office
Symbol/(703)
XXX-XXX
(DSN XXX) / email
address
Dave Looney
PhD, Research
Physiologist
/ david.p.looney4.civ@mail.mil
/ (508) 233-5027
Slide 7
25-Oct-18
7/14/2018
Select SLIDE MASTER to Insert Briefing Title Here
Methods – Study Selection
• Inclusion Criteria
–
–
–
–
–
Indirect calorimetry
Steady-state walking
1 unloaded condition
2+ loaded conditions
Load affixed to trunk
• Exclusion Criteria
– Disqualifying conditions
– Extreme environmental conditions
– Abnormal equipment
Name/Office
Symbol/(703)
XXX-XXX
(DSN XXX) / email
address
Dave Looney
PhD, Research
Physiologist
/ david.p.looney4.civ@mail.mil
/ (508) 233-5027
Slide 8
25-Oct-18
7/14/2018
Select SLIDE MASTER to Insert Briefing Title Here
Methods – Meta-regression
• Independent Variable
– Load, external load carried (% body mass).
• Dependent Variable
– ΔEE, difference between loaded and unloaded energy expenditure
(% unloaded)
• Nonlinear mixed effects meta-regression model
– ΔEE ~ a•Load^b
• Null Hypothesis
– ΔEE ~ 1.00•Load^1.00
Name/Office
Symbol/(703)
XXX-XXX
(DSN XXX) / email
address
Dave Looney
PhD, Research
Physiologist
/ david.p.looney4.civ@mail.mil
/ (508) 233-5027
Slide 9
25-Oct-18
7/14/2018
Select SLIDE MASTER to Insert Briefing Title Here
Results – Literature Search
Articles identified via electronic
databases and manual searches
(n = 354)
Abstracts excluded
(n = 300)
Full-text articles assessed for
eligibility
(n = 54)
Full-text articles excluded
(n = 35)
No unloaded condition (n = 11)
< 2 load conditions (n = 9)
Load position (n = 5)
Variable not reported (n = 8)
Outside time limits (n = 2)
Studies included in meta-regression
(n = 19)
Name/Office
Symbol/(703)
XXX-XXX
(DSN XXX) / email
address
Dave Looney
PhD, Research
Physiologist
/ david.p.looney4.civ@mail.mil
/ (508) 233-5027
Slide 10
25-Oct-18
7/14/2018
Select SLIDE MASTER to Insert Briefing Title Here
Results – Subjects & Conditions
• Subjects
–
–
–
–
n = 277 (55 women)
Age: 26 ± 7 years
Height: 175 ± 7 cm
Body Mass: 73 ± 10 kg
• Conditions
– Load: 26 ± 16% body mass
– Grade: 0 ± 6%
– Speed: 1.3 ± 0.3 m•s-1
Name/Office
Symbol/(703)
XXX-XXX
(DSN XXX) / email
address
Dave Looney
PhD, Research
Physiologist
/ david.p.looney4.civ@mail.mil
/ (508) 233-5027
Slide 11
25-Oct-18
7/14/2018
Select SLIDE MASTER to Insert Briefing Title Here
Results – ΔEnergy Expenditure (ΔEE)
Name/Office
Symbol/(703)
XXX-XXX
(DSN XXX) / email
address
Dave Looney
PhD, Research
Physiologist
/ david.p.looney4.civ@mail.mil
/ (508) 233-5027
Slide 12
25-Oct-18
7/14/2018
Select SLIDE MASTER to Insert Briefing Title Here
Results – ΔEnergy Expenditure (ΔEE)
ΔEE = 1.67 • Load ^ 1.57
± 0.13 *
± 0.09 *
* = significantly different from 1 (p < 0.01)
Name/Office
Symbol/(703)
XXX-XXX
(DSN XXX) / email
address
Dave Looney
PhD, Research
Physiologist
/ david.p.looney4.civ@mail.mil
/ (508) 233-5027
Slide 13
25-Oct-18
7/14/2018
Select SLIDE MASTER to Insert Briefing Title Here
Total Mass & Energy Expenditure
Does an 85-kg man expend as much energy when walking
as a 50-kg man carrying a 35-kg load?
85
3.6 W∙kg−1 × 85 kg
50
35
35 kg
−1
3.6 W∙kg ×50 kg× 1+1.67×
50 kg
306 W
Name/Office
Symbol/(703)
XXX-XXX
(DSN XXX) / email
address
Dave Looney
PhD, Research
Physiologist
/ david.p.looney4.civ@mail.mil
1.57
352 W
/ (508) 233-5027
Slide 14
25-Oct-18
7/14/2018
Select SLIDE MASTER to Insert Briefing Title Here
Conclusions
• Heavy loads disproportionately increase walking energy expenditure
• Assuming a linear relationship will severely underestimate the metabolic
•
costs of heavy load carriage
Each additional kg carried has a higher metabolic cost
Photograph: Courtesy of DefenseImagery.mil.
From http://www.defenseimagery.mil. VIRIN: 020212-M-7370C-126.
Photographer: CWO2 William D. Crow, USMC.
Name/Office
Symbol/(703)
XXX-XXX
(DSN XXX) / email
address
Dave Looney
PhD, Research
Physiologist
/ david.p.looney4.civ@mail.mil
/ (508) 233-5027
Slide 15
25-Oct-18
7/14/2018
Select SLIDE MASTER to Insert Briefing Title Here
Practical Applications
• Prescribing loads relative to body
•
mass will elicit more consistent
metabolic responses across groups
than absolute loads
Metabolic effects of load are better
described by the equation
– ΔEE = 1.67•Load^1.57
Photograph: Courtesy of Olive-Drab.com.
From http://www.olive-drab.com/od_history_ ww2_ops_battles_1944bulge.php.
Name/Office
Symbol/(703)
XXX-XXX
(DSN XXX) / email
address
Dave Looney
PhD, Research
Physiologist
/ david.p.looney4.civ@mail.mil
/ (508) 233-5027
Slide 16
25-Oct-18
7/14/2018
Select SLIDE MASTER to Insert Briefing Title Here
References
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
Abe D, et al. Effects of load carriage, load position, and walking speed on energy cost of walking. Appl Ergon. 2004;35(4):329-35.
Bastien GJ, et al. Effect of load and speed on the energetic cost of human walking. Eur J Appl Physiol. 2005;94(1-2):76-83.
Charteris J, et al. The 'Free-Ride‘ Hypothesis: A Second Look at the Efficiency of African Women Headload Carriers. S AFR J SCI. 1989;85(1):68-71.
Drain JR, et al. The Pandolf equation under-predicts the metabolic rate of contemporary military load carriage. JSAMS. 2017;20:S104-S8.
Duggan A, et al. Prediction of the metabolic cost of walking with and without loads. Ergonomics. 1992;35(4):417-26.
Gordon MJ, et al.. Comparison between load carriage and grade walking on a treadmill. Ergonomics. 1983;26(3):289-98.
Grabowski A, et al. Independent metabolic costs of supporting body weight and accelerating body mass during walking. J Appl Physiol.
2005;98(2):579-83.
Grenier JG, et al. Energy Cost and Mechanical Work of Walking during Load Carriage in Soldiers. Med Sci Sports Exerc. 2012;44(6):1131-40.
Griffin TM, et al. Metabolic cost of generating muscular force in human walking: insights from load-carrying and speed experiments. J Appl Physiol.
2003;95(1):172-83.
Huang TW, et al. Mechanics and energetics of load carriage during human walking. J Exp Bio. 2014;217:605-13.
Ludlow LW, et al. Walking economy is predictably determined by speed, grade, and gravitational load. J Appl Physiol. 2017;123(5):1288-302.
Looney DP, et al. Metabolic Costs of Military Load Carriage over Complex Terrain. Military Medicine. 2018;
Lyons J, et al. Influences of body composition upon the relative metabolic and cardiovascular demands of load-carriage. Occup Med (Lond).
2005;55(5):380-4.
Morin E, et al. Development of a Dynamic Biomechanical Model for Load Carriage: Phase V: Development of the Biomechanical Model by Means of
the Portable Measurement System. Queen’s Univ Kingston (Ontario) Ergonomics Research Group; 2005.
Pandolf KB, et al. Predicting energy expenditure with loads while standing or walking very slowly. J Appl Physiol. 1977;43(4):577-81.
Patton JF, et al. Physiological and perceptual responses to prolonged treadmill load carriage. USARIEM T11-90; 1990.
Pierrynowski M, et al. Metabolic measures to ascertain the optimal load to be carried by man. Ergonomics. 1981;24(5):393-9.
Puthoff ML, et al. The effect of weighted vest walking on metabolic responses and ground reaction forces. Med Sci Sports Exerc. 2006;38(4):746-52.
Sagiv M, et al. Effects of gradient and load carried on human haemodynamic responses during treadmill walking. Eur J Appl Physiol. 2000;83(1):47-50.
Santee WR, et al. A proposed model for load carriage on sloped terrain. Aviat Space Environ Med. 2001;72(6):562-6.
Schertzer E, et al. Metabolic rate of carrying added mass: A function of walking speed, carried mass and mass location. Appl Ergon. 2014;45(6):142232.
Silder A, et al. Men and women adopt similar walking mechanics and muscle activation patterns during load carriage. J Biomech. 2013;46(14):2522-8.
Soule RG, Pandolf KB, Goldman RF. Energy expenditure of heavy load carriage. Ergonomics. 1978;21(5):373-81.
Name/Office
Symbol/(703)
XXX-XXX
(DSN XXX) / email
address
Dave Looney
PhD, Research
Physiologist
/ david.p.looney4.civ@mail.mil
/ (508) 233-5027
Slide 17
25-Oct-18
7/14/2018
Select SLIDE MASTER to Insert Briefing Title Here
Thank you!
Name/Office
Symbol/(703)
XXX-XXX
(DSN XXX) / email
address
Dave Looney
PhD, Research
Physiologist
/ david.p.looney4.civ@mail.mil
/ (508) 233-5027
Slide 18
25-Oct-18
7/14/2018