Basic Physiology of Cross Country Training

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Basic Physiology of Cross Country Training

• Darrin Bright, MD

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Introduction

• Key Parameters of Aerobic Fitness
• Maximal Oxygen Uptake (VO2max )
• Running Economy
• Interaction of VO2max and Economy
• Lactate Threshold

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Maximal Oxygen Uptake - VO2max

• Defined
• Maximum amount of oxygen consumed by the body
  during one minute of exercise

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Maximal Oxygen Uptake - VO2max

• Supply versus Demand
• Determinants of Maximal Oxygen Uptake
• Cardiac Output
• Oxygen Carrying Capacity
• Skeletal Muscle Mass Oxygen Utilization

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Maximal Oxygen Uptake - VO2max

• Cardiac Output
• Stroke Volume X Heart Rate
• Adaptations of Training
• Increased Cardiac Output
• Increased Plasma Volume
• Increased Stroke Volume
• Maximal Heart Rate Unchanged
• Runners Bradycardia

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Maximal Oxygen Uptake - VO2max

• Oxygen Carrying Capacity
• Red Blood Cells
• Hemoglobin
• Erythropoietin
• Extraction

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Maximal Oxygen Uptake - VO2max

• Skeletal Muscle Mass Oxygen Utilization
• Aerobic enzyme activity
• Free fatty acid metabolism
• Capillary density

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Maximal Oxygen Uptake - VO2max

• Skeletal Muscle Mass Oxygen Utilization
• Most important in terms of training adaptation
• Muscle Fiber Type
• Type I (Slow Twitch)
• Type IIa
• Type IIx

Fast Twitch
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Physiology of Skeletal Muscle

• ATP is the Energy Source for all Muscle
  Contractions
• Three Source of ATP
• Creatine Phosphate
• Anaerobic Glycolysis
• Oxidative Phosphorylation

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Physiology of Skeletal Muscle

• Creatine Phosphate
• Minimal Amounts Stored in Cell
• Very Rapid Reaction
• Short Bursts of Speed or
  Power (10 seconds or less)

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Physiology of Skeletal Muscle

• Anaerobic Glycolysis
• Utilizes local glycogen stores
• Supplies energy for 1-3 minutes
• Lactic Acid is formed as byproduct

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Physiology of Skeletal Muscle

• Oxidative Phosphorylation
• Utilizes Glucose and Free Fatty Acids
• Exercise greater than 1 minute

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Energy Source Based on Distance
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Running Economy

• Defined
• Oxygen uptake required by a given exercise
  intensity
• Considerable variability among athletes

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Running Economy

• Affects of Training of Running Economy
• Higher values seen with
• Typical / Comfortable pace
• Older more experienced runners
• Higher weekly miles
• Improvements take time in trained athletes

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Running Economy

• Potential Adaptations with Training
• Improved muscle oxidative capacity
• Changes in motor unit recruitment
• Improved technique
• Maybe related to Elasticity / Flexibility

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Running Economy

• Methods for Improving
• Varying training pace
• Resistance Training
• Improve technique
• Possibly improve elasticity / flexibility

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VO2max and Economy

• V- VO2max
• Running speed (Velocity) at VO2max
• Highly predictive of endurance performance

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VO2max and Economy

• Morgan et. al
• Group of Trained Male Runners
• Similar VO2max 65/ml/kg/min
• Running speed at VO2max correlated highly with
  10K performance

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Lactate Threshold (LT)

• Defined
• Exercise intensity at which blood lactate levels
  increase above resting levels.
• Specific to exercise task

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Lactate Threshold

• Factors Affecting LT
• Exercise Intensity
• Training Status (60, 70, 80)
• Muscle Fiber Type
• Distribution of Workload
• Blood Lactate Clearance

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Lactate Threshold
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Lactate Threshold

• Training at LT allows high intensity stimulus
  without lactate accumulation that decreased
  training duration

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Maximal Lactate Steady State (MLSS)

• Defined
• Highest running speed at which lactate levels
  remain stable.

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Maximal Lactate Steady State (MLSS)
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Tapering
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Tapering

• What is Tapering?
• A progressive non-linear reduction of the
  training load during a variable period of time in
  an attempt to reduce the physiological and
  psychological stress of daily training and
  optimize sports performance.

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Tapering

• Goal
• Minimize accumulated fatigue without comprising
  acquired level of fitness.

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Tapering

• Proven Benefits
• Reduced Perception of Effort
• Reduced Mood Disturbance
• Reduced Perception of Fatigue
• Increased Vigor
• Improved Quality of Sleep
• Bottom-line
• IMPROVES PERFORMANCE!

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Tapering
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Type of Taper

• Stepped Taper
• Exponential Taper
• Slow Decay
• Fast Decay

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Stepped Taper
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Exponential Slow Decay
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Exponential Fast Decay
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Swimmers at Ball State

• Step Reduction
• Training reduced 67 (10,000 to 3,200 yard per
  day) for 15 days
• Times improved by 3.6
• Arm strength and power increased by 25

Costill DL, King DS, Thomas R. Effects of reduced
training on muscular power in swimmers. Physician
and Sportsmedicine. 198513(2)94-100.
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Runners at McMaster University

• Well conditioned runners
• (45-50 miles per week)
• 3 one-week tapers
• 100 Step Do nothing
• 64 Step 18 miles leisurely running
• 87 Exponential Decay (5,4,3,2,1x500m followed
  by one day of rest)
• Results
• 100 Step no improvement
• 64 Step improved time by 6
• Exponential decay improved time by 22

MacDougall JD. Medicine and Science in Sports and
Exercise, vol. 22(2), Supplement, 801, 1990
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5K Runners at ECU

• Step Reduction
• Training reduced 70 for 3 weeks
• No improvement in times or muscle power
• Exponential Decay
• Volume reduced each day for one week with 85
  decrease in weekly training volume
• Marked improvement in time and muscle power

Houmard JA, Scott BK, Justice CL, Chenier TC. The
effects of taper on performance in distance
runners. Med Sci Sports Exerc. 1994
May26(5)624-31.
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Summary

• Essential component of training
• Shorter workouts
• Maintain training intensity
• High training frequency (80 pre-taper)
• Minimizes accumulated fatigue
• Muscles are able to rebuild
• Improved Performance!

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Other Elements of Taper

• Nutrition
• Race Preparation

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Thank You