Unit 1: Measurement of Work, Power, and Energy Expenditure

Equation for Work and units

Force (N)  x distance (m) 

units: J (Joules)

Equation for Power and units

Work (J) / time (s)

units: W

Another word for Power

Work rate, Power output

What is ergometry and what does an ergometer measure?

measurement of work output. and device that measures a specific kind of work

Work and power require that ______ is moved against some _________

force; resistance

What is the force and resistance in this example: person’s body weight moving up a step against gravity

force: weight, and resistance: gravity

What is the force and resistance for Bench step

Force: weight resistance: gravity

Equation for Bench step (for work)

Force: (body mass) x (9.81)

Distance: (Z meters/step) x (Y step/time ) x ( G time)

Force x Distance

Equation for cycle ergometer (for work)

Force:   (kg resistance of pedal)

Distance:  (6 meters/revolution) x (Y revolution/time ) x ( G time)

Force times Distance

Equation for treadmill (for work)

Force:   body mass times 9.81 

Distance:  (% grade) x     ( X speed (m/time)) x ( G time)

Force times Distance

ex:       60 kg  x 9.81 =     Z       

Z x  (0.075  x  200 m/min  x 10 min ) 

How to find % grade

% grade = ( Sin θ x 100 ) = ( rise/hypotenuse x 100 )

Equation for vertical displacement

% grade times distance

Equation for Absolute VO2 and units?

Ventilation (STPD) x (Inspired O2 % - Expired O2 %) = X L/min

units: L/min

Ex: 60 L/min x (0.2093 - 0.1693) = 2.4 L/min

Equation for Relative VO2 and units?

Absolute VO2 x (1000 mL)  / body mass  = X L/min

units: mL/kg/min

Ex: 2.4 L/min x (1000 mL) ÷ 60 kg = 40 ml/kg/min

Equation for MET (resting metabolic rate) and units

Rel VO2   = X L/min

units: mL/kg/min

Rel VO2 ÷ 3.5

Ex: 37 ml/kg/min ÷ 3.5 ml/kg/min = 105 MET

Equation for WALKING energy expenditure via estimation and Units?

Horizontal: ( 0.1 x speed )

Vertical: (1.8 x speed x % grade)

Rest: 3.5 ml/kg/min

Equation: ( 0.1 x speed ) + (1.8 x speed x % grade) + 3.5 ml/kg/min

Units: ml/kg/min

Ex: (0.1 × 80 m/min) + (1.8 × 80 m/min x 0.05) + 3.5 ml/kg/min    = 18.7 ml/kg/min

Equation for RUNNING energy expenditure via estimation and Units?

Horizontal: ( 0.2 x speed )

Vertical: (0.9 x speed x % grade)

Rest: 3.5 ml/kg/min

Equation: ( 0.2 x speed ) +(0.9 x speed x % grade) + 3.5 ml/kg/min

Units: ml/kg/min

Ex: (0.2 × 160 m/min) + (0.9 × 160 m/min x 0.05) + 3.5 ml/kg/min    = 42.7 ml/kg/min

Equation for finding kcal of heat

Absolute VO2 x 5 kcal/ 1 L O2 = Z kcal/min

then

Z kcal/min x G min = A kcal

Ex:

2.4 L/min x 5 kcal/ 1 L O2 = 12 kcal/min

12 kcal/min x 30 min = 360 kcal

Equation for estimation of O2 requirement of Cycling

Rel VO2 = 1.8 x Power (kgm/min) ÷ Mass (kg) + 7 ml/kg/min

Ex:

1.8 x (736.196 kgm/min) ÷ (75 kg) + 7 = 24.7 ml/kg/min

3 parts of estimation of O2 requirement of Cycling

Resting VO2:   3.5 ml/kg/min

VO2 for Unloaded cycling:   3.5 ml/kg/min

VO2 of cycling against external load:  1.8 x (power kgm/min) ÷ (Mass kg)

Equation for % Net Efficiency (Exercise Efficiency)

(Work output) ÷ (Energy expended above rest) x 100

Equation for Gross Efficiency

(Work output) ÷ (Total Energy Expenditure) 

Equation for Running Economy

(Speed) ÷ (VO2 (energy expenditure)) 

The Net efficiency of cycle ergometry should be in what range

15-27%

Efficiency vs work rate

Efficiency decreases with increasing work rate

seen w/ curvilinear relationship btw work energy and energy expenditure

What are things that you can NOT calculate with just flat surfaces or horizontal

Work, Power, Net efficiency (b/c work is in equation), Gross efficiency (b/c work is in equation),

What are things that you CAN calculate with just flat surfaces or horizontal

energy expenditure (VO2, MET, kcal), Running economy   

Running Economy vs VO2

Lower VO2 at Same speed means Greater running economy

Running Economy definition and why is it used

oxygen cost of running at given speed and is used b/c it is hard to calculate net efficiency of horizontal running

Why can energy expenditure be estimate for horizontal treadmill walking or running and cycling?

It is b/c O2 requirements increase as a linear function of speed and power

Energy cost of horizontal treadmill walking or running (in terms of O2 and speed)

O2 requirement increases as a linear function of speed

Can you compare people’s VO2 w/ absolute VO2

No b/c Absolute VO2 does NOT take individuals’ difference in body mass, so we have to use Relative VO2

Bigger person has _____ cells, resulting in needing _____ oxygen

more cells, more oxygen

Energy expenditure is an output or input?

input

Work is an output or input?

output

Power is an output or input?

output

Food + O2 —→ Heat + CO2 + ATP + H2O

Food ——> ATP is what

metabolism (energy expenditure)

ATP ——> Output is what? and what is ATP from

mechanical energy (work + power)

ATP = Contraction (power)

3 Factors that influence exercise efficiency

exercise work rate —→ efficiency decrease as work rate/power increases

speed of movement —→ optimum speed increases when power output increases, resulting in increased efficiency

fiber composition of muscles performing the exercise —→ slow muscle fibers are more efficient

Why does change of speed of movement away from optimum results in decreased efficiency?

Low speeds of movement having low efficiency b/c of inertia, in which there is 

• increased energy cost of performing work when movements are slow and limbs must stop and start constantly

• low efficiency is linked w// high speed movement (low —> moder. work rates) b/c increasing speeds increase muscular friction and increasing internal work

Why are slow muscle fibers more efficient

It is because they need less ATP per unit of work than fast muscle fibers 

Higher efficiency is linked to _______ performance

better

Average oxygen cost of running was _______ in elite runners and ________ as ability level decreased

lowest, increased

Average difference between elite runners and untrained individuals was only 10%, suggesting

that systematic training has a limited effect on running economy

Indirect Calorimetry estimates metabolic rate via

• measurement of O2 consumption

• or CO2 consumption

• and N2 balance

(open- or close- circuit methods)

Direct Calorimetry measure metabolic rate via

heat production measurement

What is the distance and force of stairs

distance:  height of stairs, and step 

force: body weight-bearing

What is the distance and force of cycle

force: resistance on cycle (decided by you)

distance: rev/min and meter/minute

How many meters for flywheel

6 m

What is the distance and force of treadmill

distance: displacement of hip (vertical displacement)

force: foot against treadmill (vertical force)

VO2 vs Work rate

as work rate increases —→ VO2 increases

4 Expressions of Energy Expenditure

• MET (resting metabolic rate),

• Abs. VO2 (consumption of Oxygen), 

• Rel. VO2 (consumption of Oxygen), 

• kcal/min (oxygen uptake) 

isometric exercise

exercise that tighten muscles NO change in muscle length or NO joint movement

can you calculate work or power from isometric exercise

No b/c there is NO movement

—> 0 J for work. —→ no power 

What % of max HR is an indication to terminate a sub-maximal VO2 test?

85%

What % of air is oxygen?

21%

Cadence

rate of steps per minute (for bench step) 

rate of revolutions per minute (cycle ergometer)