1. Work Physiology Energy Cost of Work Learning Objective 1
State Human Factors/Ergonomic principles that influence the performance and safety of work systems (workers, equipment, and work processes).

2. Metabolism Definition Transformation: chemical energy work
Units of Measurement
kilocalorie (kcal)
1 kcal = 1000 cal = 1 Cal
= heat required to raise 1 liter H2O
from 15 °C to 16 °C

3. Alternative Units Common rate units: kcal/min Alternate rate units: W
1 W ≈ kcal/min
1 kcal/min ≈ 73 W

4. Metabolism - Components
Total Metabolism =
Basal Metabolism (life support) +
Activity Metabolism (work, leisure)

5. Basal Metabolism, Resting Metabolism
Male ( 70 kg / 154 lbs)
1700 kcal/day kcal/min
Female ( 60 kg / 132 lbs)
1400 kcal/day  1.0 kcal/min
Factors:
Sex
Size
Age
Resting metabolism ~10% - 15% higher

6. Factors Affecting Energy Expenditure
Rate of work
Posture of body
Method of work

7. Measurement O2 uptake Respiration rate (+ vital capacity) Heart rate
Activity standards

8. Energy Cost of Work

9. Grades of Physical Work
Wickens et al:
light
moderate
heavy
very heavy
extremely heavy

10. Recommended Limits Energy Expenditure (kcal/min, average)
8-hour shift 4-hour shift
Male < < 6.25
Female < < 4.20
Heart Rate (beats/min, average)
Arm work < 99
Leg work < 112

11. Rest Requirements R = rest time T = total working time
K = work metabolic rate
S = standard
metabolic rate

12. Rest Requirements: Example 1
T = 60 min
K = 6 kcal/min
S = 4 kcal/min

13. Rest Requirements: Example 2
T = 60 min
K = 10 kcal/min
S = 4 kcal/min