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Human Work and Energy Notes

This page provides notes and information on human work and energy levels


Introduction

The notes below are very simple notes identifying very approximate working and energy levels for typical UK humans.     The units used are ISO units of mechanical work. A kiloJoule is 1000 Joules and a joule defined as the energy expended (or work done) in applying a force of one newton through a distance of one metre (1 newton metre or Nm).    The dietary/nutritional energy values are normally identified using kilogram calorie (kcal ) .       ( 1 bar of dark Kit Kat has a nutritional value of 243kcal = 1013 kJ ).    The conversion factor is

1 kcal = 4,187 kJ.

the current UK normal calorie intake for a man to maintain his weight is about 2 500kcal per day = 12 217 kJ per day



Reference Standard.

BS EN ISO 8996:2004 : Ergonomics of the thermal environment. Determination of metabolic rate


Human work and energy levels.

The normal uses energy at a standard rate when lying down with an empty stomach.   The rate is called the basal metabolism and for a 70 kg man this is about 7000kJ per 24 hours.

A person also consumes energy (leisure joules) for everyday activities not associated with work rate required to do normal tasks.    The average leisure joules for a man is about 2400kJ per day.

( A man not engaged any physical activity other than light leisure activities would use about 9400kJ )

Energy is consumed for occupational activities which differ relative to the type of occupation.    The following table lists the daily energy levels related to humans involved in different employments.

Type of WorkExample MenWomen
kJ /daykJ /day
Light Work-SittingAccountant9 6008 400
Normal Manual WorkProduction Engineer12 5009 800
Moderate bodily workBricklayer 15 00012 000
Heavy manual workMiner19 500 
Extreme effortLumberjack 20 500 


Specific activities consume energy at different rates as shown below;

ActivityEnergy consumption kJ/min
Mowing Lawn30
Level Walking (5 km/hr)17
Light Gardening12-15
Digging Soil33
Walking uphill32-40
Swimming20-40
Sawing Wood28
Cycling (20 km/hr)40
Bowls16
Jogging (10 km/hr)40-48



The human energy efficiency in completing task is illustrated below:

ActivityEfficiency
Shovelling Soil (stoop)3
Screw Driving5
Shovelling Soil (upright) 6
Lifting weights9
Turning a Handwheel13
Carrying a load on back (level)- Returning without load 17
Carrying a load on back - Returning without load 20
Up and Down ladders19
Turning a Handle or a Crang21
Walking up and down stairs23
Pulling a cart24
Cycling24
Pushing a cart27
Level walking27
Walking uphill30




Links to relevant sites
  1. The estimation of metabolic heat for use in the assessment of thermal comfort...Detailed notes related to ISO 8996

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Last Updated 10/10/2012