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Extensive increase of metabolic demand while walking wearing night vision goggles in hilly terrain
KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.ORCID iD: 0000-0003-3470-5175
KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
2017 (English)In: Journal of Science and Medicine in Sport, ISSN 1440-2440, E-ISSN 1878-1861, Vol. 20, article id S77Article in journal (Refereed) Published
Abstract [en]

Introduction: The motivation for the foot-borne soldiers to carry out nighttime operations may be to reduce heat strain. We have previously found elevated metabolic demand (+7 %), and hence endogenous heat production, during walking on a flat gravel road in darkness wearing Night Vision Goggles (NVG) compared with wearing a headlamp. The aim of the present study was to evaluate the effect of wearing NVG while walking in a hilly forest terrain, and compare results between skilled and unskilled NVG users.

Methods: A group of cadets, i.e. unskilled (5 men, 6 women, age: 23±3 yrs, height: 172±10 cm, weight: 75±12 kg) and skilled NVG users (9 men, age: 26±2 yrs, height: 184±6 cm, weight: 84±5 kg) participated. At night time, subjects walked 1.1 km at a self-selected comfortable pace in a hilly forest, following a trail in the uphill part, and walking on the under bush in the downhill part. Walks were performed wearing either a headlamp (Light), monocular NVG (MNVG), binocular NVG (BNVG), or MNVG and 25 kg extra weight (backpack and body armor). Oxygen uptake, heart rate, rate of perceived exertion and walking speed were measured. To evaluate walking economy, oxygen uptake was expressed in relation to body mass and distance covered (VO2 mL·kg-1·km-1). 

Results: In both groups, VO2 (mL·kg-1·km-1) was higher in all three conditions with limited vision (MNVG; BNVG; Backpack) than in the Light condition, both during the Uphill (MNVG/BNVG; skilled: +25/+24%, unskilled: +35/+28%) and Downhill part (MNVG/BNVG; skilled: +42/+44%, unskilled: +67/+51%). In the Backpack condition, the inter-group difference in mechanical efficiency was maintained or exaggerated: Uphill (skilled: +46%, unskilled: +80%), Downhill (skilled: +70%, unskilled: +115%). The skilled NVG users walked faster, but there was no difference in heart rate between groups. In the unskilled, heart rate was higher in the MNVG and BNVG than in the Light condition during the Downhill part. Likewise, in the unskilled, the rate of perceived exertion was higher in the MNVG and BNVG than in the Light condition. 

Conclusions: Despite that in darkness foveal vision is markedly improved by NVG, it appears that the mechanical efficiency during walking in hilly terrain is markedly lower whilst wearing NVG than with full vision, regardless of whether the soldier is a skilled or unskilled NVG user.

Place, publisher, year, edition, pages
Elsevier, 2017. Vol. 20, article id S77
National Category
Physiology
Identifiers
URN: urn:nbn:se:kth:diva-219780DOI: 10.1016/j.jsams.2017.09.177OAI: oai:DiVA.org:kth-219780DiVA, id: diva2:1165334
Conference
4th International Soldiers' Congress on Physical Performance (ICSPP 2017)
Note

QC 20171213

Available from: 2017-12-13 Created: 2017-12-13 Last updated: 2018-01-13Bibliographically approved

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