Week 7 - Critical Power Flashcards
What is critical power?
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.
On the critical power curve where would you find endurance race levels of intensity?
Below the asymptote - can sustain this intensity for a couple of hours.
What three metabolic things does critical power power output sustain?
Levels of phosphocreatine, blood lactate and pulmonary oxygen uptake
Is critical power higher or lower than lactate threshold?
Higher
How does Critical power link to metabolism?
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.
Explain the link between critical power and lactate threshold
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.
What increases/decreases critical power?
Increased with endurance specific training or HIIT.
Decreased with age, disease or extreme environments e.g. altitude, presuming training stays constant over time.
What is critical speed?
The maximum sustainable speed without fatigue
What is running economy?
How is it determined?
The energy demand for a given velocity of sub-maximal running.
Determined by measuring steady-state oxygen consumption (VO2) and RER.
How would you know someone has a better running economy?
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.
Give some influences on running economy - how to improve it
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
What factors influence running economy?
Metabolic efficiency,
cardiorespiratory efficiency,
training,
biomechanical efficiency,
neuromuscular efficiency
Give examples of metabolic efficiency
Core temperature
Muscle fibre type
Substrate utilisation
Give some examples of cardiorespiratory efficiency
VO2max
HR
Minute ventilation
Give some examples of biomechanical efficiencies
Flexibility
Kinetics - movement forces
kinematics - acceleration etc.
Gait
Give some examples of neuromuscular efficiencies
neural signalling
force production
stiffness
What is relative intensity?
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
Which foot strike is the most economical?
Midfoot/forefoot
7% more than rear foot.
High stride angles more economical
Are smaller or larger moment arms in lower limbs more efficient?
Shorter Achilles moment arm - less flexibility in lower limb joints.
What is cycling efficiency?
The energy demand for a given velocity of cycling
The link between ATP turnover and external power output.
Biomechanical factors that influence cycling efficiency
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
Give some biomechanical factors that DO NOT influence cycling efficiency
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
Physiological factors that influence cycling efficiency
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.
