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).

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

Alternative Units Common rate units: kcal/min Alternate rate units: W 1 W ≈ 0.014 kcal/min 1 kcal/min ≈ 73 W

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

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

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

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

Energy Cost of Work

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

Recommended Limits Energy Expenditure (kcal/min, average) 8-hour shift 4-hour shift Male < 5.00 < 6.25 Female < 3.35 < 4.20 Heart Rate (beats/min, average) Arm work < 99 Leg work < 112

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

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

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