1 / 26

Work Physiology

Work Physiology. A.H. Mehrparvar, M.D. Yazd University of Medical Sciences Department of Occupational Medicine. Metabolism. A set of chemical processes allowing cells to live Nutrients: carbohydrates, lipids, proteins ATP: energy currency of the body exists in all cells

hollee-wiley
Download Presentation

Work Physiology

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Work Physiology A.H. Mehrparvar, M.D. Yazd University of Medical Sciences Department of Occupational Medicine

  2. Metabolism • A set of chemical processes allowing cells to live • Nutrients: carbohydrates, lipids, proteins • ATP: • energy currency of the body • exists in all cells • Two energetic bonds • Each mole: 12000 calories

  3. Metabolism • Two kinds: • Anaerobic (only for carbohydrates): • Phosphagen system • Reserved ATP (for 1-2s) • Phosphocreatine (for 5-8s) • Glycolysis (for 1 m.) • Each molecule of glucose: 2 ATP • Each molecule of glycogen: 3 ATP • Aerobic (carbohydrates, lipids, proteins)

  4. Endurance: Phosphagen:8-10 s Glycogen: 1-2m Aerobic: unlimited ATP production in unit time: Phosphagen: 4 moles Glycogen: 2.5 moles Aerobic: 1 mole Comparing different systems

  5. Anaerobic metabolism • At the biginning of the activity • Low concentration of O2 • 1 mole glucose: 24000 calories (3%) • Glucose → pyrovic acid → lactic acid

  6. Aerobic metabolism (carbohydrates) • Oxidative metabolism • Glucose → pyrovic acid + 2 ATP • Pyrovic acid → acetyl coA + H2O + CO2 • Acetyl coA → CO2 + H + 2 ATP (Krebs cycle) • Oxidation of hydrogens (oxidative phosphorylation): 30 ATP • 1 mole glucose: 686000 calories • 1 mole glucose: 38 ATP (456000 calories)

  7. Aerobic metabolism • More than 95% of energy • For short-time contractions: 50% from carbohydrates • For long-time contractions: mostly from lipids

  8. Metabolic rate • Heat produced by chemical reactions • In average 27% of the energy of nutrients is used (73% produces heat) • Energy units: • calorie (gram calorie): energy needed to 1°C increase the temperature of 1g water • Calorie (KC): 1000 calories

  9. Energy sources: • Carbohydrates: 45% • Lipids: 40% • Proteins: 15% • Energy requirements: BMR + ADL + leisure activities + work activities

  10. BMR = 1650 KC: dependent on: • Height and weight • Age • Gender • Hormones • Temperature • sleep • + Eating: 1850 KC • + sitting: 2000-2250 KC • Heavy working: 6000-7000 KC

  11. BMR: 65-79 KC/h • Sitting: 100 KC/h • Standing: 105 KC/h • Typing: 140 KC/h • Walking: 200 KC/h • Running: 570 KC/h • Climbing stairs: 1100 KC/h

  12. Musculoskeletal system during work • Maximum muscle power reduces during work • E.g.: • About 50% after 1 minute • Muscle endurance: • Dependent on: • Muscle glycogen • Consuming carbohydrates

  13. Metabolic systems in muscles (phosphagen, glycogen, aerobic) • Reconstruction of systems: • PK → ATP • Glycogen → PK and ATP • Aerobic → glycogen PK and ATP • O2 debt → aerobic

  14. At the biginning of activity: • Anaerobic metabolism • Aerobic metabolism of carbohydrates • Aerobic metabolism of lipids (after 4-5 h) • Aerobic metabolism of proteins • Anearobic metabolism

  15. Respiratory system during work • Average O2 consumption during rest: 250 mL/min. • Activity: ↑ rate and depth of respiration • Average O2 consumption during activity: 3600-5000 mL/min. • Diffusion capacity of O2 during rest: 23 mL/min. • Diffusion capacity of O2 during activity: 80 mL/min.

  16. Respiratory system is not limiting during activities

  17. Cardiovascular system during work • Blood flow to muscles (rest): 3.6 mL/min • Blood flow to muscles (work): 90 mL/min • Cardiac output (rest): 5.5 L • Cardiac output (work): 30 L • During work: • ↑ Blood flow to muscles • ↑ stroke volume (50%) • ↑ heart rate (270%)

  18. Maximum heart rate: 220 – age • Effect of activity on maximum heart rate: ?

  19. Measurement of metabolism • Direct calorimetry • Measurement of heat produced • Indirect calorimetry • Measurement of consumed O2 • Consumption of O2 an estimate of consumed energy • More than 95% of energy from aerobic metabolism • 1L consumed O2 → 4825 c energy (energy equivalent of O2)

  20. Physical capacity • Aerobic capacity: an estimate of physical capacity • Maximum heart rate: an estimate of aerobic capacity esp. in average activities • Maximum heart rate is not appropriate for light or heavy work • Maximum aerobic capacity: VO2max

  21. VO2 max • Amount of O2 consumed in the point of maximal aerobic metabolism • Units: • 1 Met = 3.5 ml/Kg/min • 1 Met = 1 Kcal/Kg/hour

  22. Sedentary work (<2 met) • Lifting less than 4.5 kg, office work, work with light objects • Light work (2-3 met) • Lifting less than 9 kg, frequent lifting of objects <4.5 kg • Medium work (4-5 met) • Lifting less than 23 kg, frequent lifting of objects <11 kg

  23. Heavy work (6-8 met) • Lifting less than 45 kg, frequent lifting of objects <23 kg • Very heavy work • Lifting more than 45 kg, frequent lifting of objects >23 kg

More Related