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 N�m).    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 Work Example Men Women kJ /day kJ /day Light Work-Sitting Accountant 9 600 8 400 Normal Manual Work Production Engineer 12 500 9 800 Moderate bodily work Bricklayer 15 000 12 000 Heavy manual work Miner 19 500 Extreme effort Lumberjack 20 500

Specific activities consume energy at different rates as shown below;

 Activity Energy consumption kJ/min Mowing Lawn 30 Level Walking (5 km/hr) 17 Light Gardening 12-15 Digging Soil 33 Walking uphill 32-40 Swimming 20-40 Sawing Wood 28 Cycling (20 km/hr) 40 Bowls 16 Jogging (10 km/hr) 40-48

The human energy efficiency in completing task is illustrated below:

 Activity Efficiency Shovelling Soil (stoop) 3 Screw Driving 5 Shovelling Soil (upright) 6 Lifting weights 9 Turning a Handwheel 13 Carrying a load on back (level)- Returning without load 17 Carrying a load on back - Returning without load 20 Up and Down ladders 19 Turning a Handle or a Crang 21 Walking up and down stairs 23 Pulling a cart 24 Cycling 24 Pushing a cart 27 Level walking 27 Walking uphill 30

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