Standard Operating
Procedure
Equipment /
Procedure:
Cycle Ergometry – Monark Ergometers
Filename:
2012.1214SOP_cycle_ergometry_on_monarks
Assessor’s
name & date:
Reviewer’s
name & date:
Review Date:
Richard Metcalfe, December 2012
Rebecca Toone, December 2012
December 2014
2012.1214SOP_cycle_ergometry_on_monarks
Cycle Ergometry – Monark Ergometers
Safety Information:
 Prior to performing exercise bouts with participants you must have read
the following risk assessments:
o 2013.0124RA_exercise_ergometry
This standard operating procedure provides information on how to calculate a
number of important variables when using Monark cycle ergometers.
General Information about Monark Ergometers:
The Monark Ergometer is a friction-based device meaning that the work-rate
depends on the resistance applied to the flywheel basket and the pedal
frequency. The flywheel basket weighs 1 Kg (Figure 1A) and resistance is
increased by adding free weights to the basket (Figure 1B). The saddle height
and position of the handle bars can be adjusted using the appropriate levers
(Figure 2).
A
B
Figure 1 – Monark Flywheel Basket without (A) and with (B) weights.
2012.1214SOP_cycle_ergometry_on_monarks
A
B
Figure 2: Levers for adjusting handle bars (A) and Saddle Height (B)
The Monark ergometer is portable but must be handled carefully. To move
the ergometer, first ensure the flywheel basket is lowered and secure
(otherwise the rope is prone to slip off the flywheel), then tilt the ergometer
onto its wheels (from the front) using the handlebars. DO NOT LEAN ON
THE PROTECTIVE PLASTIC COVERING OF THE ERGOMETER.
1. Calculating Work-Rate
The Monark ergometer is a friction-braked device. Therefore, work-rate
depends on both the resistance applied and the pedal frequency. Pedal
frequency is maintained, while the amount of resistance applied is varied. It is
important that subject’s cycle as close to 60rpm as possible for the duration of
all exercise tests.
Work = force x distance
Force = mass (kg) x acceleration m.s-2
The force acting on a mass of 1kg at normal acceleration of gravity is 1
kilopond (kp), which equals 9.81 Newtons (N)
The flywheel circumference is 1.622m. Therefore, the force is exerted over a
distance of 1.622m during each flywheel revolution. As a result, when a mass
of 1kg is applied to the ergometer, the work done per flywheel revolution is:
(1 x 9.81 x 1.622) Nm = 15.9 Nm or 15.9 J
Each time the pedal turns, the flywheel turns 3.7 times. Therefore, if a subject
cycles at exactly 60 rpm, the flywheel turns 222 times (3.7 x 60). Subjects are
2012.1214SOP_cycle_ergometry_on_monarks
instructed to cycle at 60 revolutions per minute, and therefore work must be
converted into a rate (J.s-1 or watts).
(1 J.s-1 = 1 watts)
222 x 15.9
= 58.8 J.s-1 or watts
60
Using the flywheel counters fitted on the cycle ergometers it is possible to
determine the exact number of times that the flywheel turns during a given
amount of time. This figure should be entered into the above calculation in
place of the number 222.
2. Calculating Mechanical Efficiency
Metabolism during exercise is not 100% efficient at turning the energy derived
from the catabolism of substrates into mechanical work. Indeed, it is relatively
inefficient, and approximately 70-80% of available energy is released as heat,
with only 20-30% being utilised for positive work. It is possible to calculate
how efficient the body is at a particular activity:
Mechanical Efficiency (%) =
Work rate (kJ.min-1)
Exercise-induced metabolic rate (kJ.min-1)
x 100
n.b. Exercise-induced metabolic rate is the product of exercising metabolic
rate – resting metabolic rate. Also, note that workrate is expressed in kJ.min-1,
which is converted from watts or J.s-1 to kJ.min-1 by multiplying by 60 and
dividing by a 1000.
3. Calculating Relative Exercise Intensity
The responses to exercise are largely governed by the relative intensity of a
particular exercise, not the absolute intensity. Exercise at the same absolute
work-rate (e.g. 100 W) will provoke very different responses in different
subjects. Although the absolute level of work will be similar, and therefore the
absolute oxygen cost also similar, the demands may be very different if
expressed as a proportion of each individual’s maximum oxygen uptake.
Relative exercise intensity may also be assessed in terms of heart rate at
relative exercise intensity.
 2 is known at a number of submaximal work-rates, then the linear
Once VO
relationship between oxygen uptake and work-rate can be determined. If this
 2 max),
is coupled to each individual’s personal maximum oxygen uptake ( VO
2012.1214SOP_cycle_ergometry_on_monarks
 2 max may be derived. A similar relationship
then a relative percentage of VO
may be determined for heart rate (should be treated with more caution).
A worked example of how to calculate relative exercise intensity:
Workrate (W):
 2 (l.min-1)
VO
 2 max (l.min-1)
VO
88 120 147 178
1.45 1.84 2.08 2.49
3.5
 2 (put on the horizontal axis on this occasion),
1. Plot workrate against VO
and derive a linear regression equation between these variables. This will
enable the calculation of the workrate (y) required to elicit a certain
percentage of maximum oxygen uptake. For the example above, the
equation would be: y = -39.942 + 88.164 (x).
 2 max that is required (e.g. 50%). In the
2. Calculate the percentage of VO
example above, this would be 1.75 l.min-1.
3. Substitute this value (1.75) into the regression equation derived for your
subject
e.g. y = -39.942 + 88.164 (1.75). Therefore, the workrate required to elicit
 2 max is 114 W.
50% of VO
4. Assuming that pedal revolutions will be 60 rpm (222 flywheel revolutions),
calculate the actual mass that must be applied in order to elicit 114 W.
Applied mass (kg) =
WR (W) x 60
9.81 x 1.622 x 222
Using the example given above, this would mean that 1.94 kg must be
applied to the flywheel in order to produce a power output of 114 W, which in
turn should elicit 50% of maximal oxygen uptake.
End of Document
2012.1214SOP_cycle_ergometry_on_monarks