Week 7 - Critical Power

Question 1

What is critical power?

Answer 1

The power asymptote of the relationship between power and time to exhaustion

It is the max aerobic power you have as you deplete all the metabolic power you have in the first 10-15 seconds of the test.

Question 2

On the critical power curve where would you find endurance race levels of intensity?

Answer 2

Below the asymptote - can sustain this intensity for a couple of hours.

Question 3

What three metabolic things does critical power power output sustain?

Answer 3

Levels of phosphocreatine, blood lactate and pulmonary oxygen uptake

Question 4

Is critical power higher or lower than lactate threshold?

Answer 4

Higher

Question 5

How does Critical power link to metabolism?

Answer 5

Critical power is the highest metabolic rate that can be sustained exclusively by aerobic metabolism. It happens at higher intensities than the lactate threshold.
In the test you drain all your anaerobic power in the first 30 seconds, at 2-3 minutes you are using exclusively aerobic metabolism.

Question 6

Explain the link between critical power and lactate threshold

Answer 6

Lactate threshold occurs below critical power.
At lactate threshold your blood lactate levels start to increase exponentially, but you can still continue to exercise at this intensity.
Critical power is a power output level after lactate threshold that you can continue to exercise at.

Question 7

What increases/decreases critical power?

Answer 7

Increased with endurance specific training or HIIT.
Decreased with age, disease or extreme environments e.g. altitude, presuming training stays constant over time.

Question 8

What is critical speed?

Answer 8

The maximum sustainable speed without fatigue

Question 9

What is running economy?
How is it determined?

Answer 9

The energy demand for a given velocity of sub-maximal running.
Determined by measuring steady-state oxygen consumption (VO2) and RER.

Question 10

How would you know someone has a better running economy?

Answer 10

If an athlete can run at a given speed using less oxygen, oxidising less glucose and burning more fats (lower RER) they are more efficient.

Question 11

Give some influences on running economy - how to improve it

Answer 11

Endurance training - fartlek (randomly changing the speed/intensity - stresses both aerobic and anaerobic systems).
Low intensity exercise for long periods
Resistance training
Nutrition - high nitrate diet
Stretching
Environment

Question 12

What factors influence running economy?

Answer 12

Metabolic efficiency,
cardiorespiratory efficiency,
training,
biomechanical efficiency,
neuromuscular efficiency

Question 13

Give examples of metabolic efficiency

Answer 13

Core temperature
Muscle fibre type
Substrate utilisation

Question 14

Give some examples of cardiorespiratory efficiency

Answer 14

VO2max
HR
Minute ventilation

Question 15

Give some examples of biomechanical efficiencies

Answer 15

Flexibility
Kinetics - movement forces
kinematics - acceleration etc.
Gait

Question 16

Give some examples of neuromuscular efficiencies

Answer 16

neural signalling
force production
stiffness

Question 17

What is relative intensity?

Answer 17

The percentage of VO2 max an athlete can work an event
E.g. different intensities are required for a marathon vs a 1 mile race but both are aerobic, endurance events

Question 18

Which foot strike is the most economical?

Answer 18

Midfoot/forefoot
7% more than rear foot.
High stride angles more economical

Question 19

Are smaller or larger moment arms in lower limbs more efficient?

Answer 19

Shorter Achilles moment arm - less flexibility in lower limb joints.

Question 20

What is cycling efficiency?

Answer 20

The energy demand for a given velocity of cycling
The link between ATP turnover and external power output.

Question 21

Biomechanical factors that influence cycling efficiency

Answer 21

Saddle height - greater saddle height - more efficient
Saddle angle - a seat tube angle of 80 degrees is more efficient than a smaller angle
Cadence - cycling at a lower RPM results in greater oxygen consumption than a self-selected optimal

Question 22

Give some biomechanical factors that DO NOT influence cycling efficiency

Answer 22

crank length
fore-aft position of foot
pattern of force application

The last two are just what is comfortable for each cyclist after years of riding

Question 23

Physiological factors that influence cycling efficiency

Answer 23

Muscle fibre type - more type I fibres = more efficient
UCP3 (uncoupling proteins) - detach oxphos from ATP synthesis. Trained muscle has lower UCP3 and greater efficiency. - ideally we want oxphos and ATP synthase to be coupled.
SERCA1/SERCA2 - transfers calcium from cytosol to sarcoplasmic reticulum during contraction in an ATP consuming process. Less SERCA with training.