John W. Castellani, Ph.D. Thermal & Mountain Medicine Division

1. Prescribing Exercise for Cold-Weather Environments John W. Castellani, Ph.D. Thermal & Mountain Medicine Division US Army Research Institute of Environmental Medicine Natick, MA 01760 john.castellani@us.army.mil

2. Outline How cold is it? Physiological responses to cold Does cold change the FITT principle? Safety and prevention of cold injuries CV disease & asthma

3. How cold is cold? Ambient temperature

4. Wind Chill Temperature Index National Weather Service, 2001

5. Immersion

6. Cold-Wet

7. Protection Against the Cold • Physiological Adjustments • Vasoconstriction (Heat Conservation) • Shivering (Heat Production) • Behavioral Thermoregulation • Wear Clothing • Seek Shelter • Utilize Heat Sources • Exercise

8. S = M - (±W) ± R ± C ± K ± E Gisolfi & Wenger

9. Cold alpha-adrenergic mediated constriction reduces cutaneous blood flow lower skin temperature lower skin to ambient temperature gradient reduced heat loss

11. A D J U S T A B L E C I R C U L A T O R Y I N S U L A T I O N M R M E X M T G A D J U S T A B L E P E R I P H E R A L C I R C U L A T O R Y I N S U L A T I O N M M INSULATION A D J U S T A B L E S U R F A C E F I L M I N S U L A T I O N T S K C C T TRUNK AND HEAD 1 T A T R U N K C O R E S K I N F I X E D I N S U L A T I O N F A T A N D B O D Y S T R U C T U R E M U S C L E B L O O D F L O W A D J U S T A B L E S U R F A C E F I L M I N S U L A T I O N T S K EXTREMITIES T A C T S K I N 2 M E X E X T R E M I T Y T G F I X E D I N S U L A T I O N C O R E F A T A N D B O D Y S T R U C T U R E T - T T - T C S K S K A

12. Lowering Of Peripheral Skin Temperatures Causes Cold-induced Vasodilation O’Brien, J. Appl. Physiol., 2005

13. Shivering Metabolic Heat Production (W·m-2) Tcore = 35.8°C Tskin = 21°C Castellani et al., J. Appl.Physiol., 1998

14. METS REST 6 MPH JOG SHIVERING 12°C Tsk 35°C core MAX EXERCISE Comparison Of Metabolic Costs

15. Shivering Is Related To Exercise Intensity AMBIENT CONDITIONS TEMPERATE COLD OXYGEN UPTAKE ~ 60% VO2max POWER OUTPUT

16. Stroke Volume Increases During Cold Air Exposure (5°C) STROKE VOLUME (L) EXPOSURE TIME (min) Muza et al. , 1988

17. 130 ▼ ▲ 22.5°C Heart Rate (bpm) ▼ ▲ 100 5.5°C ▼ ▲ 70 Oxygen Uptake (ml/min) 200 600 1000 1400 Hanna et al., 1975

18. Cold Vasoconstriction Increases TPR And BP Epstein et al., NEJM, 1969

19. Increased Afterload And Increased Work Of Heart Epstein et al., NEJM, 1969

20. Cold Acclimitization Young, Handbook of Physiology, 1996

21. Cold Acclimation Effects On Skin Temperature Skin temperature (°C) Exposure Time (min) Young et. al, 1986

22. Physiological Responses: Modifiers

23. Individual-Related Factors • Low Body Fat • Fatigue & Fitness • Dehydration • Age • Alcohol • Sleep Loss • Nicotine • Illness • Poor Nutrition • Poor Clothing/Equipment • Prior Cold Injury

24. Less Subcutaneous Fat = Greater Fall In Rectal Temperature FALL IN RECTAL TEMPERATURE (°C) 10 5 4 6.7 20 MEAN SKINFOLD THICKNESS (mm-1) Keatinge, 1960

25. Metabolic Rate During Cold Air Exposure As A Function Of Physical Fitness 1°C M [ W·m-2 ] . VO2 max [ ml· min-1·kg-1 ] Bittel et. al, 1988

26. Skin Temperature During Cold Air Exposure As A Function Of Physical Fitness 1°C Tsk [ °C] . VO2 max [ ml· min-1·kg-1 ] Bittel et. al, 1988

27. Dehydration has no effect on whole-body thermoregulation O’Brien et al., J. Appl. Physiol. 1998

28. Hypohydration & CIVD euhydration O’Brien & Montain, J. Appl. Physiol., 2003

29. Aging Blunts The CIVD Response To Cold FINGER SKIN TEMPERATURE °C IMMERSION DURATION, min Mathew et. al, 1986

30. Exercise Prescription • Enhance physical fitness • Promote health by reducing risk for • future development of disease • Ensure safety during participation in exercise ACSM, Guidelines for Exercise Testing & Prescription, 4th Edition

31. Does Cold-Weather Affect How We Prescribe Exercise? Cardiovascular Resistance Exercise Flexibility Safety of Participants

32. Cardiovascular Conditioning No change Frequency Intensity Time Type To achieve same HR at low work, need to work harder No change No change

33. Heart Rate Related To Exercise Intensity? AMBIENT CONDITIONS TEMPERATE COLD Heart Rate ?? POWER OUTPUT

34. Risk Reduction & Prevention of Cold Injuries

35. Risk Management 1. Identify Hazard How cold is it? • 2. Assess Hazards • Analyze Mission Requirements • Determine Uniform & Equipment • Identify High Risk People 5. Supervise Evaluate & Correct Controls 4. Implement Controls Adopt & Implement Controls into Plans 3. Develop Controls Implement Cold Mitigation

36. Hypothermia Avoidance

37. Risk Factors

38. Exercise in the Rain Thompson & Hayward, 1996

39. Cold-Weather Clothing Creating a microenvironment

40. Clothing Principles • Insulation • Use loose layering to trap air • Keep clothing dry • Ventilation • Avoid overheating • Evaporate moisture • Environmental Protection • Windproof, waterproof

41. Layering & Fabrics Inner layer – thin layer against the skin to wick moisture Mid-layer – primary insulation Outer shell – windproof, waterproof, breathable Limited vapor transfer rate; Use pit zips, side zips to ventilate Cotton – absorbs moisture; heavy / bulky when wet; slow to dry Wool – absorbs moisture; heavy / bulky when wet; coarse fibers resist compression thus retain insulation when wet Polypropylene – fibers do not absorb any moisture - wicks by capillary action; lightweight; quick drying; melts in high heat Polyester – treated to be hydrophobic; wicks moisture; lightweight; quick drying; melts in high heat Nylon – absorbs moisture; wind resistant; quick drying Leather – absorbs water, dries slowly. Treat for water repellency

42. Cold Weather Clothing System

43. Clothing Requirements ISO, 1993

44. Example: 3 METS, 0°F, what clo needed?

45. Keys to Working in Cold Weather No sweat Remove & add layers Be aware of weather changing Know your athletes/clients limits Encourage people to speak up

46. Frostbite Avoidance

47. Wind Chill Temperature Index National Weather Service, 2001

48. Does finger respond to exercise in cold (-10°C)? Dexterity Threshold Mäkinen et al. Comp. Physiol. Biochem., 2001

49. Does nose respond to exercise in cold (-10°C)? Gavhed et al. Int. J. Biometerol., 2003

50. Caloric Requirements 10-40% higher (?) • Why? • Expend more energy - combination of clothing & • equipment & terrain • Shivering if get cold enough