HB 100: First Year Physiology

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HB 100 First Year Physiology

• Training for aerobic fitness

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Aims

• To appreciate different types of exercise,
  delimited by intensity.
• To understand the differences in stress and
  adaptation to different intensities of aerobic
  training.
• To appreciate practical rules that help in
  exercising at the correct intensity.

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Optimal training improvements
Physical Performance
Time

• Different types of overload cause different
  physiological adaptations

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Quantifying Intensity for aerobic training

• Borg scale (RPE)
• Perceived percentage of maximal effort
• Heart rate (HR monitors)
• Lactate threshold
• velocity (minute / mile pace)
• Power (SRM cranks)

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The two most important factors for endurance
performance are

• High rate of transport of oxygen (delivery)
• Ability to utilise that oxygen (utilisation)

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Central (delivery) and peripheral (extraction and
utilisation) adaptations ultimately leads to an
enhanced capacity for the aerobic production of
ATP
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Categorising Exercise Intensity

• Moderate - no elevation of blood lactate
  (production rte equals removal rate). Complete
  Long Slow Distance (LSD) runs at this intensity.
• Heavy - begins at lactate threshold and ends at
  the maximum lactate steady state (MLSS). Zone in
  which threshold training occurs.
• Severe - above MLSS up to maximal oxygen uptake.
  Perform aerobic interval training in this domain.

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Methods of training

• Continuous
• long/ultra long distances
• threshold runs
• Intermittent
• Long intervals
• Short intervals
• fartlek

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RPE Borg Scale

• Rating
• 6
• 7 Very, very light
• 8
• 9 Very light
• 10
• 11 Fairly light
• 12
• 13 Somewhat hard
• 14
• 15 Hard
• 16
• 17 Very hard
• 18
• 19 Very, very hard
• 20

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Classification of exercise intensity based on 20
to 40 minutes of endurance activity comparing
three methods
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Long Slow Distance Training

• Running at 50-60 VO2 max, for 15-250 km (for
  highly trained athletes).
• Designed to increase the the ability of the
  active musculature to utilise fat (reservation of
  glycogen stores).
• Trains volume and distance tolerance. Ability to
  cope with structural damage and metabolic
  disturbance of long distance or high volume.

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Heavy intensity exerciseLactate Threshold (LT)

• LT the point at which blood lactate
  concentration suddenly and continually begins to
  increase (often expressed as a velocity or power
  output).
• Seen as important for endurance performance,
  because it represents the maximum intensity at
  which exercise occurs, without a rise in lactate
  and associated fatigue (hydrogen ions).

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Lactate Threshold
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Maximum Lactate Steady State

• The highest running speed (intensity) at which
  blood lactate concentration, although elevated,
  can be stabilised.

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Adaptations to Threshold Training

• It is believed that changes to threshold are a
  result of a different mechanism than changes to
  VO2 max.
• Changes in threshold are likely to come
  predominantly from local/peripheral changes, in
  the trained muscle (e.g. increased mitochondrial
  content, preferred utilisation of fats and other
  enzymatic changes, increased capillary density).
• Little is known about the optimum intensity to
  improve LT, but continuous training for 20-40
  mins at a level just above LT has been
  traditionally used.

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Severe Intensity Exercise

• Above maximal lactate steady state (MLSS).
• High intensity at which fatigue quickly sets in.

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Aerobic Intervals

• Because this level of exercise results in fairly
  rapid fatigue, it can only be performed for a
  limited period.
• To ensure an adequate volume of exercise takes
  place at this level, we perform intervals with an
  active recovery in between bouts.
• We run at or close to VO2 max for 4 minutes, then
  4 minutes of active recovery (a very low level)
  allow us to perform the next bout at the same
  intensity.
• Traditionally athletes will complete 3-6 bouts of
  severe intensity exercise in a session.

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Aerobic Intervals

• Provides variation in training.
• Allows volume of severe intensity exercise to be
  increased due to recovery.
• Thought to stimulate predominantly central
  adaptations. No clear evidence to support this.

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Adaptations to endurance training

• Endurance training increases aerobic power
• Level of increase effected by trained status
• Average 10 - 20 improvement in aerobic power
• Large individual differences in training responses

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Health Benefits of aerobic exercise

• Delays the infirmities and disabilities of old
  age
• higher bone mass density and fewer osteoporotic
  fractures
• improved self-esteem and confidence in performing
  daily tasks for elderly people
• Protects against diseases
• reduces risk of developing CHD
• lowering of blood pressure
• better weight lose than dieting alone
• reduces risk of heart attacks in obese people
• lower incidence of non-insulin diabetes
• better management of insulin diabetes
• Improved functional capacity

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Reversibility principle

• Detraining occurs rapidly post training.
• After only 2 weeks significant physiological and
  metabolic reductions have been demonstrated to
  occur.
• After 20 days bed rest aerobic power decreased by
  25 (Saltin et al. 1968, Circulation 38 suppl.)
• similar decrement in maximal stroke volume
• similar decrement in maximal cardiac output
• similar decrease in capillary density

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• Mitochondrial enzymes
• anaerobic threshold
• capillary density
• heart, blood distribution
• anaerobic threshold
• fine control
• mobilization of fatty acids
• control of liver glycogen gt glucose

100m 400m 1km 3km 10km 20km 30km 40km REST
Recovery from tissue damage
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Further Reading

• Foss Keteyian (1998) Chapter 12 (p296-324)
• Questions 8 - 14
• Wilmore and Costill (1994) Chapter 6 (p193 -
  201)
• Questions 2-5, 8