Lecture 3 Flashcards
Ergometry = measuring force, work and power
what is a definition of ergometry
the measurement of mechanical energy production
what is force
resistance to overcome
what is work
volume of exercise
what is power
intensity of exercise
what is an ergometer
a device from which work and power can be determined
three things you would assess with an ergometer
fitness = strength, power, endurance
clinical or research = bodies response to stress
ergonomics = energy cost of activities
three ways you know if you are assessing something appropriately
validity (relevance) and accuracy (get the right number) and reliability (reproducible)
what is strength
force = mass x acceleration
the maximum force that can be produced by a muscle group in a single movement which depends on …..
what does strength depend on
- muscle size
- fibre orientation
- fibre type proportions
- neural activation
- metabolic factors
what is work and the equation for it
the energy imparted into an object when it is moved to a position of higher potential energy
work = force x displacement
in exercise acceleration often relates to …
- gravity
- body mass
- equipment
what is power and the equation for it
the rate of doing work
power = work / time
what does power depend on
- the ability to supply energy fast
- on strength
- on resistance not being too high (so velocity not too low)
what is power often expressed relative to
- body mass or lean body mass (watts/kg)
- upper limit attainable (% peak power output)
what is endurance
the ability to maintain force or repeated contractions
what does endurance depend on
- energy
- strength
- motivation
- injury
- thermoregulation
- efficiency
more….
equation of efficiency and what does it range from, also what is needed to calculate it
efficiency = work rate / metabolic rate x 100
it ranges from 0-25%
can only calculate when can measure power output
what is the resistance used in air-braked ergometers
resistance is usually of wind vanes to movement through air
what happens to resistance and work rate when cadence increases using air braked ergometers
resistance and so workrate increases exponentially with cadence (rpm)
what are the pros and cons to air braked ergometers
pros = relatively cheap
cons =
- difficult to calibrate
- need to know barometric pressure
how do friction (mechanically) braked ergometers work
apply a known mechanical resistance against a flywheel
what happens to work rate as cadence increases on friction braked ergometers
as cadence increases, so does work rate = linear relation
what are the pros and cons to friction braked ergometers
pros
- easy to use, calibrate and calculate
- relatively cheap, portable and robust
cons
- limited precision of work rate control, reduces reliability
what happens to resistance compared to cadence in electromagnetically braked ergometers
resistance varies inversely with cadence
what are the pros and cons of electromagnetically braked ergometers
pros
- wide power range
- fine control of power
- allows setting of constant power output, or varies patterns
- decrease measurement error by increased reliability within and between species
cons
- can be expensive
what are the pros and cons of treadmill ergometry
pros
- can be highly specific e.g runners
- encourages central rather than peripheral fatigue
cons
- cost and size
- variable in running efficiency, therefore less certainty in energy expenditure if its not measured
