Ergometry & Calorimetry

 

Ergometry and Calorimetry

•      Give us the ability to quantify:

–   Work and power output (ergometry)

–   Energy expenditure (calorimetry)

–   Exercise intensity!!

 

Measurement of Work

•      Ergometry

–    Science that measures mechanical work

–    Work = F x D

•   Force applied against gravity over a distance

 

Measurement of Work

•      Ergometer

–    Device that can be used to measure work

–    Bench step

•   Earliest ergometer

•   D = the step height x step rate x time

•   F = body mass (kg)

Work = 70 kg x 0.25 m/step x 30 steps/min x 30 min

              = 70 kg x 225 m

              = 15,750 kgm

 

Measurement of Power Output

•      Power

–    Work expressed relative to time

   

    Work  =  15,750 kgm

            P          =  15,750 kgm / 30 min

                        =  525 kgm/min

    

Work & Power

Work

 

•      Lifting a 5 kg weight up a distance of 2 m

Work = force x distance

Work = 5 kg x 2 m

Work = 10 kgm

 

Measurement of Work and Power

•     Cycle ergometery

–    D = distance traveled/rev (6 m/rev*)

–    F = resistance (Kp or Kg)

*  6 meter per revolution is a constant with most cycle ergometers

–    For example:

•    Pedaling at 95 rpm (6 m/rev) with 2.5 kg of resistance for 30 minutes

Work = 95 x 6 x 2.5 x 30

                         = 42,750 kgm

Power = 42,750 kgm/30 min

                         = 1425 kgm/min

What is this power output in Watts??

Power = 1425 kgm/min/6.118

                         = 233 W

 

Measurement of Work and Power

•      Treadmill ergometry

–   More difficult to apply ergometry principles

–   Level walking or running

•   Doesn’t involve moving a force against gravity

 

Measurement of Work and Power

•      Ergometry

–   Can be used to better understand:

•   Energy expenditure and energy cost of performing specific exercise on ergometers

–   Cycle ergometry at 1250 kgm/min

      for 45 min:

 

1250 kgm/min = 204.315 Watts = 3.0 kcal/min = 12.5 kJ/min

AND…..

3.0 kcal/min x 45 min = 135 Kcals

     (MECHANICAL COST !!!!)

 

Calorimetry

•      The science that quantifies heat release from metabolism

•      Direct calorimetry

–   Measurement of heat production as an indication of metabolic rate

•      Indirect calorimetry

–   Measurement of oxygen consumption as an estimate of resting metabolic rate

 

Calorimetry

Open-circuit Indirect Calorimetry

•      Fundamental Principles

–   Volume of oxygen consumed (VO2)

•   Equal to inspired - expired O2 volumes

–   Volume of carbon dioxide produced (VCO2)

•   Equal to expired - inspired CO2 volumes

•       Let’s calculate VO2!!!!

 

The non-protein caloric equivalents for RQ

 

If fat provides a greater store of energy, why does CHO provide more energy relative to VO2?

 

Metabolic Calculations

•      Useful for estimating energy expenditure when indirect calorimetry is not available

–   Walking, running, cycling (leg or arm), stepping

•      Sum of:

–   Horizontal + Vertical + Resting

•   Metabolic costs

•      Based on linear relationship between:

–   Power output & VO2

ACSM Metabolic Calculations

•      Walking

 

VO2 ml/kg/min =

 

    3.5 ml/kg/min                                            (Resting)

                  +

    Speed (m/min) x 0.1                            (Horizontal)

                  +

    Grade (decimal) x Speed (m/min) x 1.8 (Vertical)

ACSM Metabolic Calculations

•      Running

 

VO2 ml/kg/min =

 

    3.5 ml/kg/min                                            (Resting)

                  +

    Speed (m/min) x 0.2                            (Horizontal)

                  +

    Grade (decimal) x Speed (m/min) x .9 (Vertical)

 

ACSM Example

•      Beau is dribbling at top speed, 3 mph, up a hill with 5% grade.  What is his VO2?

•      Resting = ?

–    3.5 ml/kg/min

•      Horizontal = ? 1 mph  = 26.8 m/min

–    3.0 x 26.8 x 0.1 = 8.04

•      Vertical = ?

–    0.05 x 80.4 x 1.8 = 7.24

•      VO2 = ?

–    3.5 + 8.04 + 7.24 = 18.74 ml/kg/min !!

 

ACSM Metabolic Calculations

•      Leg Ergometry

    

VO2 ml/min = (10.8 x W / M) + 7

 

W= Watts

M = body weight in kg

 

 

 

Leg Ergometry Example

•      Rosa is pedaling up Sandia Crest at 80 rpm, and 3 kg resistance.  She weighs 65kg.  What is her VO2? 

•      First Watts needs to be calculated

–   80rpm x 6m/rev x 3kg = 1440kgm

–   1440 / 6.118 =  235 Watts

 

–   VO2 = (10.8 x 235 / 65) + 7

•   VO2 = 46 ml/kg/min

 

Efficiency vs Economy

•      Mechanical Efficiency

–   Percentage of total chemical energy used for external work

•   ME (%) = mechanical work /energy expended

•   For example:

–   13,300 kgm on cycle ergometer MW
–    Cost 25 L O2
–   25 x 4.9 (RQ caloric equiv.) = 125.5 kcal
–   125.5 x 426.4 = 52,234 kgm (kcal to kgm)
–   13,300/52,234 x 100 = 25.5%

•   Human locomotion efficiency

–   5 – 25%

 

Calculation of Exercise Efficiency

•      Net efficiency

 

•      Net efficiency of cycle ergometry

–   15-27%

Factors That Influence Exercise Efficiency

•      Exercise work rate

–   Efficiency decreases as work rate increases

•      Speed of movement

–   There is an optimum speed of movement and any deviation reduces efficiency

•      Fiber composition of muscles

–   Higher efficiency in muscles with greater percentage of slow fibers

 

Relationship Between Energy Expenditure and Work Rate

Efficiency vs Economy

•      Economy of Movement

–   Comparing O2 cost of same work between two or more individuals

–   The lower the VO2 the better the economy

–   Several factors influence economy

–   Important during long-term athletic events

Economy of Movement

 

Calorimetry

•      Direct Calorimetry

–   Direct measurement of heat in a chamber

•   Change in temp of water circulating through chamber

–   Very expensive!!!

–   Body is good at storing heat (unreliable!)

•   During exercise

–   Best for measuring BMR