adaptations to aerobic exercise

Question 1

acute responses to aerobic exercise

Answer 1

• Ventilation: Increases d/t neural input and feedback from central and peripheral receptors
• Heart Rate: Increases d/t reduced PNS influence and increased sympathetic drive and hormonal effects
• Stroke Volume: Increases d/t increased SNS drive (increased contractility) and increased EDV
• Blood Pressure
  o SBP increases d/t increase in cardiac output
  o DBP remains unchanged or may decrease
  o slightly d/t vasodilation
• Redistribution of blood flow
• Oxygen consumption

Question 2

O2 deficit responses to aerobic exercise

Answer 2

O2 deficit is the difference between the oxygen requirement and the oxygen utilistation at the commencement of exercise.
- EPOC. Excess Post Exercise Oxygen Consumption.
o Increased oxygen consumption due to increased metabolic demand post exercise (Increased HR and ventilation, Replenishing Mb stores, Increased body temperature, Anabolic processes)

• How does training affect O2 deficit?
• How does EPOC change with exercise intensity?

Question 3

aerobic training

Answer 3

• Improves the ability to sustain a particular level of physical effort
• Occurs via improvements in functional capacities related to oxygen transport and utilisation
• Fick equation VO2 = Q x a-vO2 difference
• Central adaptations: Increase Q
• Peripheral adaptations: Increase a-vO2 difference

Question 4

central adaptations (HR and SV)

Answer 4

- How do we increase Q?
Heart Rate
o Reduced at rest and during
o submaximal exercise
o Training increases vagal tone 
o Lower cardiac O2 cost
o Permits greater filling time

Stroke volume
- Increases with training d/t increased left ventricular volume and mass
- Increased SV
o Load placed on the heart during contraction (EDV (Preload), Afterload = pressure in the wall of the left ventricle during ejection, i.e. higher blood pressure)

Question 5

central adaptations (plasma volume and blood flow)

Answer 5

Plasma volume

• Increase of ~10-20% following 3-6 aerobic training sessions
• Increased EDV
• Increased SV
• Temperature regulation
• Subsequent increase in Hb

Blood flow
- Distribution of blood flow to more oxidative muscle fibres
- Reduced splanchnic and renal blood flow
- Increase in skeletal muscle blood flow
o d/t increase in cardiac output and increase in cross-sectional area of capillaries

Question 6

peripheral adaptations

Answer 6

Mitochondria 
- Increase size and number
- Increased oxidative enzymes in the mitochondria
o e.g. citrate synthase
o d/t tissue hypoxia

Capillaries
- Increased number of capillaries
o d/t increased shear stress (pressure) on capillaries
- Results in increased O2 delivery
o Increased transit time
o How does this increase muscle oxygenation?

Fibre type
Type IIx –> Type IIa –> Type I

Myoglobin
- Possibly small increase in intramuscular myoglobin content

Question 7

adaptations to aerobic training (response determined by)

Answer 7

• Magnitude of response is determined by
  o Genetics
  o Previous training status
  o Training load (Training load = Training intensity x volume)

Question 8

aerobic performance (Determined by)

Answer 8

Determined by
- VO2 max, Critical Power, Economy

VO2max
o The highest rate that oxygen can be taken up and used by the body during exercise
o A result of both central and peripheral adaptations to training

Anaerobic threshold
o Power Speed/pace/power at “threshold” is perhaps the most important determinant of endurance performance

o Closely linked terms: Critical power, Ventilatory Threshold, Lactate Threshold, MLSS (Maximum Lactate Steady State)

Question 9

when does anaerobic threshold occur

Answer 9

o ~40-60% VO2max in untrained individuals
o ~70-75% VO2max in trained individuals
o Up to 80-90% VO2max in elite marathon runners
o Up to 85-90% VO2max in elite distance swimmers
o ~60-85% VO2max in sprint athletes

Question 10

critical power

Answer 10

• Defn: Maximum Intensity at which work can be sustained indefinitely
• But practically ~60mins
• Critical Power (CP)
• Note: W’ is NOT AWC as shown in the diagram

Question 11

ventilatory threshold

Answer 11

Intensity of exercise where a non-linear increase in VE is observed
o inc CO2
o inc H+

CO2 + H2O H2CO3 HCO3- + H+

Question 12

lactate threshold

Answer 12

• Intensity of exercise where lactate begins to accumulate in the blood
  o Lactate production outstrips utilisation
  o Associated with inc H+

training causes threshold to occur at a higher work rate

Question 13

implications for performance

Answer 13

• Why is CP/ AT a more important determinant of performance than VO2max?
• Consider 2 athletes with the same VO2max (4.0 L.min-1)
• AT of athlete A = 70% of VO2max and athlete B = 85% of VO2max
• Athlete B will be able to maintain a higher work rate before H+ and CO2 begin to accumulate in the blood

Question 14

training to improve aerobic threshold

Answer 14

Largely peripheral adaptations

• Increased capillary density
• Increased mitochondria
• Changes in LDH and PDH enzymes (Decreased lactate production)
• Increased myoglobin content
• Increased fat utilisation

Train at ~AT for prolonged periods of time

• Often referred to as “tempo” or “threshold” training
• Be careful with volume