1 / 36

Occupational Physiology

Occupational Physiology. Hardianto Iridiastadi, Ph.D. Aerobic Capacity. Definition Highest oxygen uptake an individual can attain (VO 2 max) Also known as maximal aerobic power Power = energy available / unit of time Measurement Douglas bag 1 liter O2 ~ 4.7 – 5.05 kcal

ferdinand
Download Presentation

Occupational 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. Occupational Physiology Hardianto Iridiastadi, Ph.D.

  2. Aerobic Capacity • Definition • Highest oxygen uptake an individual can attain (VO2 max) • Also known as maximal aerobic power • Power = energy available / unit of time • Measurement • Douglas bag • 1 liter O2 ~ 4.7 – 5.05 kcal • Metabolic analyzer

  3. Aerobic Capacity From National Institute for Occupational Safety and Health. (1981). A Work Practices Guide for Manual Lifting, Technical Report No. 81-122. Cincinnati, OH: U.S. Department of Health and Human Services (NIOSH) Fig 4.1

  4. Aerobic Capacity • NIOSH (1981) • Male: 15 kcal/min (~3 l/min) • Female: 10.5 kcal/min (~2.1 l/min)

  5. Aerobic Capacity

  6. Aerobic Capacity –Maximal Test • Max (direct) method • Begin at low level • Increase workload until VO2max is reached • Increase in workload does not increase VO2 • Occurs at max HR (~220-age) • Extreme dangers inherent to this method (push systems to their limit • Cannot perform on at risk persons

  7. Aerobic Capacity – Sub Maximal Test • Indirectly measure the maximum aerobic capacity – less fatiguing and less dangerous, but much less accurate • Method assumes a linear relationship between heart rate and oxygen consumption (dot indicates rates) • If VO2 = f(HR), then HRmax -> VO2 max - > Emax

  8. Aerobic Capacity – Sub Maximal Test • Max heart rate (HR) could be predicted by Max HR = 220 – age, or = 206 – (0.62 x age), or = 190 – (0.62 x (age – 25)) Note, Max HR prediction • Has errors (up to 10 bpm) • Not suitable for children

  9. Measuring Aerobic Capacity • Methods • Treadmill • Cycle ergometer • Step test, nomogram • Need to involve large muscle groups • Treadmill test • Higher (5 – 11%) AC for inclined treadmill • 7% greater than ergocycle

  10. Aerobic Capacity vs Demographics • Gender effect • No differences before puberty • Female ~ 65 – 75% of male’s • Age effect • Peak at 18 – 20 years of age • AC at 65 yo ~ 75% at 25 yo • Jobs • Lower AC among white collar employees

  11. Aerobic Capacity vs. Performance • High AC not neccessary for high performance, due to other factors: • Training • Experience • Psychological state • Techniques • AC can be increased for another 10 year via training

  12. Maximum Heart Rate • Concept: • Indirect measure of energy • Increased heart rate ~ increased energy production (assumed) • Direct measurement • Indirect Measurement • MaxHR = 206 - (0.62 x age) • MaxHR = 220 – age • MaxHR = 190 – 0.62(age – 25)

  13. Workload Assessments Should be based on capacity!

  14. Workload Assessment • Direct measurement • Calorimetric chamber • Indirect measurement • Rate of oxygen consumption (l/min) (representative of metabolic process) • Indirect measurement • Heart rate (bpm) (linearly related to oxygen consumption)

  15. Workload Assessment • Energy cost

  16. Workload Assessments HR – Oxygen relationship (Kroemer, 1997)

  17. Workload Assessment • Energy cost (Kamalakannan et al, 2007) E-cost = -1967 + 8.58HR + 25.1HT + 4.5A – 7.47RHR + 67.8G E-cost: Energy cost (Watt) HR: Working heart rate (bpm) HT: Height (inch) A: Age (yrs) RHR: Resting heart rate (bpm) G: Gender (m = 0; f = 1) 1 Watt ~ 0.0143 kcal/min

  18. Workload Assessment • Energy cost (Keytel, 2005) E-cost = -55.0959 + (HR x 0.6309) + (W x 0.1988) + (A x 0.2017) E-cost: Energy cost (kJoule/min) HR: Working heart rate (bpm) W: Weight (kg) A: Age (yrs) 1 KJoule/min ~ 0.239 kcal/min

  19. Workload Assessments

  20. Workload Assessment • Energy cost (Indonesian, male) VO2 = -1.169 + 0.02HR – 0.035A + 0.019W (Adj.R2 = 78.1%) • VO2 = oxygen consumption (l/min) • HR = heart rate (bpm) • W = weight (kg) • A = age (20 – 40 yrs)

  21. Workload Assessment • Energy cost (Indonesian, female) VO2 = -1.991 + 0.013HR + 0.024W (Adj.R2 = 63.6%) • VO2 = oxygen consumption (l/min) • HR = heart rate (bpm) • W = weight (kg) • A = age (20 – 40 yrs) • VO2max = 3.7 ± 0.55 l/min

  22. Workload Assessments • Example • Male • 30 years old • 165 cm • 65 kg • Working HR = 100 bpm • Resting HR = 65 bpm

  23. Workload Assessment *20 – 30 years old %HRReserve (HRR) = 100% x (HRave – HR-rest)/(HRmax – HRrest)

  24. Workload Assessments From: Wickens (2004)

  25. Workload Assessments • Physical Activity Ratio (PAR) • Light – Less than 3 x resting energy • Heavy – About 6 to 8 x resting energy • Maximal – More than 9 x resting energy

  26. Workload Assessment • Borg’s Ratings of Perceived Exertion (RPE)

  27. Workload Assessments • Borg’s Category Ratio (CR) 10 0 - Nothing at all 0.5 - Extremely weak • - Very weak 3 - Moderate 5 - Strong 7 - Very strong 10 - Extremely strong

  28. Fatigue • Concept • Workload > 30 – 40% of work capacity • Likely experienced at end of shift • Certainly occur when workload > 50% capacity • Associated with • Tiredness, exhaustion, etc. • Impaired performance • Increased lactic acid; lower blood glucose • Lower job satisfaction and increased health risks • Could be due to other factors (motivation, poor health, etc.) • HR > 110 after 30 – 60 min of rest

  29. Fatigue • Short term • VO2 max • Long term • 33% max (8 hours) • 60% max (1 hr/shift) • NIOSH • 1981: 3.5 kcal/min for 8 hrs acceptable by 99% of M, 50% of F, 75% of total • 1991: 3.1kcal/min if lifting from <30"; 2.2 kcal/min if lifting from >30" to ‘protect’ 50% of F and 99% of M

  30. Fatigue and Rest

  31. Controls for Demanding Work • Engineering • Decrease load weights • Elevate low-lying loads • Reduce walk/carry distances • Control heat • Decrease frequencies • Seated work • Lifting aids, ...

  32. Controls for Demanding Work • Administrative • Work-rest schedules • productivity • acceptability • feasibility • length of rest breaks (many small better than few long breaks) • Team work • Fatigue Monitoring • productivity, discomfort surveys, HR monitoring • Worker Selection • compare capacity with job energy demands

  33. Controls for Demanding Work • Rest period R = (Ework – Erec)/(Ework – Erest) E ~ Oxygen consumption R: % of work time

  34. Controls for Demanding Work Example PWC = 5 kcal/min Ejob = 6.5 kcal/min Erest = 1.5 kcal/min Rest = 30% of work duration

  35. Controls for Demanding Work • Adequate supply of water and sugar • Training (strength vs. endurance)

  36. Changes with Endurance Training • Low force, high repetition training • increased SVmax => increased COmax • incr. efficiency of gas exchange in lungs (more O2) • incr. in O2 carrying molecule (hemoglobin) • increase in #capillaries in muscle

More Related