Physiology of Exercise (PED 30W) – Lab 1
Ergometry Lab:
Ergometers: Ergometers are devices which measure work. In your labs you will often use cycle
ergometers. Recall that one way to calculate work is:
Force * Distance = Work
Force:
On older cycle ergometers the force component of work was readily apparent. These devices
were built such that pedaling the ergometer caused a weight containing basket to be elevated.
The force component of work was changed by adding or removing weights from the basket.
Thus, if the basket held 2 kg of weight, it was readily apparent that the force component of the
work was 2 kg. On most modern ergometers the force is no longer applied in this manner; it
typically comes in the form of frictional resistance. For example, a strap might be applied to the
flywheel to increase friction. The amount of resistance can be altered by tightening or loosening
this strap. The ergometer is calibrated and the frictional force applied can be read from a dial on
the side of the device. In this case, since there is no actual weight present, it is correct to refer to
the resistance in kiloponds (kp), rather than kilograms (kg). A kp is the force associated with 1
kg at normal gravitational acceleration.
Distance:
Since we are dealing with stationary cycle ergometers the device as a whole is not moving.
However, keeping in mind that the resistance is applied to the flywheel, we can measure distance
as the distance which a point on the flywheel travels through space. On a Monark ergometer,
one full revolution of the pedals will cause a point on the flywheel to move 6 meters through
space. Therefore we can calculate the distance (meters per minute) portion of our formula by
multiplying 6 meters by the number of revolutions per minute (rpm). If the pedal rate is 50 rpm
then the distance traveled would be 300 meters per minute (50 * 6), if 70 rpm then 420 meters
per minute (70 * 6) and so on. The value of 6 meters per revolution of the flywheel applies to all
Monark ergometers.
Since, as we saw before, work is equal to Force * Distance we can now calculate work as
follows:
Force (kp) * Distance (meters/min)
=
Work (kpm/min)
If the frictional resistance is set at 2 kp and the pedal rate is 50 rpm, then the work performed
would be 600 kpm/min (2kp * 50 rpm * 6 meters). Work may also be expressed in Watts. A
Watt is equal to approximately 6 kgm/min, thus dividing work in kgm/min by 6 will convert to
Watts. Therefore, 600kpm/min is approximately equivalent to 100 Watts (600kpm/min divided
by 6).
Ergometry Lab
Name _____________________________
Date__________
wt (kg)________
sex___
age_______
ht (cm)________
temp (C)_________
Important subject characteristics:
Adjust seat height for subject as follows: with the heel of the foot on the pedal and the pedal in
the down position the leg should be as close to straight as possible (about 5º of knee flexion).
Set metronome to double the desired rpm (e.g., 100 for 50rpm). The subject should pedal to the
cadence such that each click of the metronome coincides with one of the subject's legs pushing
down on the pedal. Set the desired resistance using the dial on the side of the ergometer.
Calculate work in kpm/min for each of the above workloads then convert to Watts.
min
rpm
*
0-1
50
distance/rev *
(m)
__________
1-2
50
__________
2-3
60
3-4
4-5
resistance
(kp)
0.5
=
work
(kpm/min)
________
Watts
______
1.0
________
______
__________
1.0
________
______
60
__________
1.5
________
______
70
__________
1.5
________
______
Allow the subject to rest while the resistances and pedal rates needed to achieve the following
workloads are calculated. Then have the subject perform the desired workloads.
min
rpm
*
0-1
____
distance/rev
(m)
__________
1-2
____
__________
2-3
____
3-4
4-5
*
resistance
(kp)
____
=
work
(kpm/min)
720
Watts
______
____
________
30
__________
____
________
100
____
__________
____
270
______
____
__________
____
________
45