This document describes Mosso's ergography experiment to study human fatigue. The experiment uses Mosso's ergograph apparatus to measure the work done by voluntary contractions of the forearm muscles by lifting weights over time. It details the objective to define ergography, calculate work done, and study the effects of venous and arterial occlusion on fatigue onset. The procedure instructs setting up the apparatus and having subjects rhythmically lift weights while contractions are recorded until fatigue prevents further lifting. Calculations determine work done and fatigue time under normal circulation and with venous or arterial occlusion. The findings show occlusion decreases work and hastens fatigue by inhibiting nutrient delivery or waste removal from muscles.

1. Mosso’s Ergography
Dr. Ravi Dutt (MBBS, MD)
Senior Resident
Department of physiology
MAMC, Delhi
*with video explaining the apparatus and procedure

2. Student’s Objective
After completing the practical, the students should be able to :
1. Define Ergography.
2. Explain the physiological significance of this practical.
3. Calculate the work done using Mosso’s ergograph.
4. Enlist the factors affecting fatigue and work done.
5. Explain the effect of Venous and arterial occlusion on work
done.

3. AIM
• To study the phenomenon of human fatigue and to calculate the work
done using Mosso’s ergograph.
• To study the effect of arterial and venous occlusion on the onset of
fatigue by using Mosso’s ergograph

4. Introduction
• Mosso’s ergography is done to record the voluntary isotonic
contractions of a skeletal muscle.
• The erg is the unit of work and ergograph is the apparatus used for
recording voluntary contractions of skeletal muscle in humans.
• The Mosso’s ergograph is employed not only to assess the
performance of hand and forearm muscles but also to study the
phenomenon of fatigue and the factors that affect fatigue.

5. APPARATUS
• Mosso’s Ergograph
• Meteronome
• Kymograph
• Paper, Pen marker and Ink
• Weights
• Sphygmomanometer

6. Principle
Concept of Human Fatigue:
• Fatigue is defined as a temporary and reversible loss of the
physiological property of contraction of skeletal muscles .
• Fatigue may be subjective i.e. feeling of a sensation of tiredness
or objective i.e. measurable decrement in performance .
• These two phenomenon's are dependent on each other.
• The development of fatigue in voluntary contacting muscles can be
shown by lifting a weight in Mosso’s ergograph.

7. Mosso’s Ergograph

8. Mosso’s Ergograph
• It consists of a flat wooden board with 2 pairs of clamps and curved plates to fix,
hold, and steady the forearm of the subject .
• There is a pair of metal tubes (finger holders) for fixing index and ring fingers in
position. The middle finger remains free to be connected to a thick cord and
hook.
• A hook (for suspending weights) is attached to a cord, is made to hang over the
pulley. The other end of the cord is attached to a sliding plate which moves to and
fro.
• A sliding plate carries a lever system to record muscle exertions on a kymograph
cylinder. The other end of the plate is connected through a sling to the middle
finger of the hand.
• Alternatively the sliding plate can carry a chart paper on which a pencil or
ballpoint pen can record the contractions

9. Mosso’s Ergograph video description

10. Meteronome
• It is a timing device which
functions as a variable
interrupter to deliver the
sounds at a preselected
frequency.
• For this experiment , the
sound frequency is to be set at
30 beats/min

11. Procedure
• The Mosso’s ergograph is set on a table of suitable height. Explain the procedure to
the subject and seat her/him beside the table.
• Fix the forearm on the ergograph, and insert the index and ring fingers in the finger
holders and ensure movement of only middle finger.
• Put a suitable weight usually of 2 kg on the weight stand and place the kymograpgh
with paper such that the movements of sliding plate can be recorded on it.
• Keep the speed of kymograph drum at 2.5 mm /sec. Adjust the beat of the
metronome at 30/minute, i.e. one beat every 2 seconds, and set it oscillating.
• Put the middle finger in the hook and ask the subject to pull the cord by flexing the
middle finger maximally and rhythmically, following each beat of the metronome.
• continue the procedure until fatigue is so great that the weight can no longer be
lifted. Label the graph with weight with which it was done.
• After a rest of 15 min, repeat the procedure with increased weight(2.5 and 3kg)
following the same steps.

12. Video of Mosso’s Ergography Procedure

13. Effect of venous and arterial occlusion
Effect of venous occlusion.
• After a rest of 15 min, apply the BP cuff on the upper arm and raise the pressure
to 40 mm Hg to stop venous return.
• Repeat the whole procedure as before. Fatigue sets in earlier because of
accumulation of waste products in the exercising muscles.
Effect of arterial occlusion.
• After another period of rest of 15 min, raise the pressure of the cuff till the
disappearance of radial pulse (130-140 mm Hg) to stop arterial and venous
occlusion.
• Tell the subject to repeat the procedure. Fatigue sets in much earlier now
because there is not only an accumulation of waste products but also a deficiency
of oxygen and other nutrients.

14. CALCULATIONS
• The work done (W) in each of the
above cases may be calculated by
the below formula:
• W= F x D
W= work done( in kg meters)
F= weight lifted (in kg)
D= total distance moved (in meters)
To get the total distance (D) moved,
measure the total length of all
vertical lines.

15. Alternatively,
• D= No. of contractions x average
height of contractions(A) where
Area of triangle[1/2 base(b) x height(h)] +
area of reactangle [length(a) x breadth(h)]
A= ___________________________________
Total lenghth of base (a +b)

16. Calculation of onset of fatigue (in Min.)
• For this , Measure the total horizontal distance moved till the onset of
fatigue and labeled it as X in each case.
• As the speed of the drum is 2.5 mm/sec, so
2.5 mm distance is covered in ------------ 1 sec
1 mm distance is covered in --------------- 1 / 2.5 sec
So, X distance is covered in ----------------- 1 /2.5 * X sec

17. Result Table
S. NO. WEIGHT (IN kg) Metronome
frequency
Work done (in kgm) Fatigue time in Min
1. 2 30/min
2. 2.5 30/min
3. 3 30/min
Effect of venous and arterial occlusion on onset of fatigue
Effect of increasing weight on onset of fatigue and work done
S. No. Circulation Metronome
Frequency
Weight constant
(kg)
Onset of fatigue in
Min
1. 30/min
2. 30/min
3. 30/min

18. Physiological significance
• The degree , duration and type of work done are the important
factors that affect the onset of fatigue. Onset of Fatigue depends on:
• The weight to be lifted
• Frequency of contractions
• Motivation
• Blood supply to contracting muscles
• Training
• Environmental factors such as temperature and humidity

19. • The fatigue developing in maximal voluntary muscular efforts, first
occurs in Central nervous system, followed by Neuromuscular junction
and lastly in muscle proper.
• The performance of a person can be increased by encouragement and
motivation. This shows that fatigue has a cortical component.
• Venous occlusion decreases the work done due to accumulation of
metabolites in the muscle.
• Arterial occlusion further decreases the work done and brings in an
early onset of fatigue as it prevents the supply of nutrients to the
muscle.

20. References
• Ghai’s Text book of Practical Physiology (9th edition) Revised
& edited by Dr. V.P. Varshney and Dr. Mona Bedi
• Essentials of MD/DNB Physiology Practical Examination by
Dr. A.K. Jain
• Comprehensive Text book of Physiology by Dr. G.K.Pal

21. Thank You