Physiology of a CrossCountry Athlete

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Physiology of a Cross-Country Athlete
MITCA Cross Country Clinic 08

• Ross Sherman Ph.D., M.Sc.
• Associate Professor Exercise Science

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Outline

• Personal background
• Substrates
• Energy metabolism
• Physiological adaptations
• Respiratory
• Cardiovascular
• Muscular
• Model of a cross-country athlete
• Summary

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My background

• Failed High School athlete
• 800m 154
• 1500m 404
• 5 k 1458
• Education
• Ph.D. University of Bath, England
• M.Sc. Loughborough University, England
• Experience
• Exercise Physiologist
• Track athletics, cycling, rowing, soccer,
  triathlon
• World 50 male squash player
• Fitness and training expert Mens Health, Total
  Football

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Outline

• Personal background
• Substrates
• Energy metabolism
• Physiological adaptations
• Respiratory
• Cardiovascular
• Muscular
• Model of a cross-country athlete
• Summary

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Energy substrates

• Carbohydrate
• Predominant in high intensity ex
• 4.1 kcal per g
• Fat
• Low to moderate intensity ex
• 9.4 kcal per g
• Protein
• 5-10 during prolonged ex
• 4.1 kcal per g

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Outline

• Personal background
• Substrates
• Energy metabolism
• Physiological adaptations
• Respiratory
• Cardiovascular
• Muscular
• Model of a cross-country athlete
• Summary

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Energy metabolism

• Three systems
• Immediate
• ATP-Phosphocreatine (ATP-PCr) system
• Short term
• Glycolytic system
• Long term
• Oxidative system

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Energy metabolism

• Immediate Energy
• ATP-PCr system
• Provides up to 15 seconds of energy
• Driven by breakdown of ATP and phosphocreatine
• All-out sprint
• Requires no oxygen - anaerobic

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Energy Metabolism

• Short Term Energy
• Anaerobic glycolysis
• No oxygen needed
• Provides up to 2 min all-out exercise
• Fast delivery
• Breakdown of stored carbohydrate
• Glucose / glycogen

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Energy Metabolism

• Long Term Energy
• Aerobic glycolysis and oxidation
• Breakdown of carbohydrates and fats
• Glucose, glycogen, triglycerides
• Fat more energy production
• Provides endless energy
• BUT slow delivery

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Interaction of systems
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Outline

• Personal background
• Substrates
• Energy metabolism
• Physiological adaptations
• Respiratory
• Cardiovascular
• Muscular
• Model of a cross-country athlete
• Summary

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Physiological adaptations

• Respiratory
• ? maximal oxygen uptake (VO2max)
• ? diffusion
• ? oxygen extraction at the tissues
• ? pulmonary ventilation at max
• ? tidal volume
• ? respiratory rate
• Respiratory muscles have high fatigue resistant
  not performance limiting

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Physiological adaptations

• Cardiovascular
• Left wall hypertrophy
• ? contractile function
• ? stroke volume
• ? HR at rest and sub-max faster recovery
• ? cardiac output
• ? blood flow to muscles

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Physiological adaptations

• Cardiovascular (cont.)
• ? blood pressure at rest and sub-max
• ? blood volume
• ? plasma volume
• ? red blood cell volume
• ? hemoglobin (oxygen carrying component)

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Physiological adaptations

• Muscular
• ? size of Type I fibers
• Transition towards Type I characteristics
• ? number of capillaries
• ? myoglobin content (oxygen transport)
• ? mitochondria (source of ATP production)
• ? oxidative enzyme activity
• ? capacity of oxidative metabolism

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Outline

• Personal background
• Substrates
• Energy metabolism
• Physiological adaptations
• Respiratory
• Cardiovascular
• Muscular
• Model of a cross-country athlete
• Summary

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Physiological profiles

• Mayers and Gutin (1979)
• Pre-pubertal boys 8-11 years of age
• VO2max 57 ml.kg-1.min-1
• High utilization of fat during submax. work
• High anaerobic capacity
• Anaerobic capacity running economy related to
  best mile time NOT VO2max

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Physiological profiles

• Sundberg and Elovainio (2008)
• At 12-14, performance NOT related to VO2max
• 16 year olds similar to adult runners
• VO2max 66 ml.kg-1.min-1
• Lung volume 5.3 l
• Resting heart rate 62 beats.min-1
• Partly due to adaptations from training

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Physiological profiles

• Gore, C.J. (2000)
• Elite Australian male runners (gt 5k)
• Height 178 cm / 510
• Body mass 64.0 kg / 141 lb
• Sum of 7 skinfolds 36 mm
• VO2max 65-80 ml.kg-1.min-1

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Physiological profiles

• Winter et al. (2007)

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Outline

• Personal background
• Substrates
• Energy metabolism
• Physiological systems
• Respiratory
• Cardiovascular
• Muscular
• Model of a cross-country athlete
• Summary

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Summary

• Predominant energy substrate fat
• Carbs and protein may play a role
• Oxidation of fat yields most energy
• Carbs used for high intensity bursts
• Metabolic, cardio-respiratory and muscular
  systems all influence running performance/capacity
  
• Positive adaptations in all these systems with
  aerobic/endurance training
• Marked training effects seen in late teens
• Distinct physiological profile