Two Early Dynamometers

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This article was published in the: Journal of the Neurological Sciences, 1978, 37; 127 – 134, by
John Pearn and is posted with permission from Elsevier.
John Pearn, The Royal Children’s Hospital, Brisbane, Queensland 4029 (Australia)
(Received I2 January, 1978)
(Accepted 24 February, 1978)

An account of two of the earliest dynamometers is presented, together with results of the first
experiments attained with them. The Graham-Desaguliers dynamometer was developed in
London in 1763 to measure human muscular force, in such a way that synergistic muscles could
not impart a false mechanical advantage to the test. The Regnier dynamometer was invented in
Paris in 1798 to measure the traction properties of artillery-horses, but was designed as an allpurpose
instrument to measure specific human muscle groups as well. Dynamometers were
developed to record human strength along a continuum, to remove the need for a dead weight
or biological standard, and to measure many different groups of muscles, not just those of lifting
or pushing. The foundations of modern clinical dynamometry are described.

Before the beginning of the eighteenth century, human muscular strength was tested by the
ability to lift or move standard weights. In 1699 De la Hire had recorded that the thigh muscles
could lift 140 French pounds, and that "as for the Strength of the Arms for drawing and lifting a
weight, one may suppose it of 160 pounds". Comparative tests of muscular force, as opposed to
absolute measurements, were also well standardized at that time. Sir Jonas Moore "compared
together the Strength of Men and Horses' using a capstan, a method long used for ship-board
games when activity was slack, and morale falling because of enforced idleness".
These two methods for the measurement of human strength each had obvious disadvantages.
Firstly, there was no agreed international standard for weight, and thus no real chance of
comparison other than within the local populace. As late as 1763 Desaguliers (a French-born
Englishman) noted, in the context of a comparative study of the strengths of leg muscles of the
English and the French, that "the French libre is betwixt one 11th and one 12th Part greater than
our Pound Averdupoids" (Desaguliers 1763a). A second difficulty was that only certain groups
of muscles could be tested, and that it was impossible to standardise body position or lifting
technique. It was well known at the time that fairground feats of apparently inexplicable strength
by strong- men could be partly explained by using tricks of mechanical advantage. A lecture
given in London at this time described how "about 15 years ago a German of middle Size, and
but ordinary Strength ... by these Contrivances (i.e. mechanical advantage of different body
positions) pafs'd for a Man of uncommon strength, and got considerable Sums of Money by the
daily Concorse of Spectators" (Desaguliers 1763b).
The third major difficulty was that the use of dead-weights did not allow a practical scale of
strength to be used; no real recording of a continuum was possible, and hence the sensitivity of
the strength tests was limited to the series of weights available. Finally, the comparative study of
strength by such biological techniques of using an- other person or persons at a capstan, or at
an Indian-wrestle, or by a tug-of-war was obviously too gross and unverifiable for any serious
scientific endeavour, and un- thinkable for medical use.
In the early 18th Century a need had arisen for a technique that would measure muscle strength
that would record along a continuum, that would allow easy standardization and reproducibility,
and that would be sensitive. This need arose from two quite separate sources. The first was a
growing anthropological curiosity about strength differences between the sexes, and between
different races. Moore had written early in the century "I have observed that five English
Labourers are equal to an Horse, and only seven French Men or as many Dutch Men". This
type of provocation was obviously too much for the celebrated Buffon, who later in the century
sent a Parisian doctor, Francois Peron, to Australia to undertake a series of comparative studies
there (Peron and Freycinet 1807).
The second theme necessitating the better quantitation of muscular power arose, like so many
discoveries, because of military necessities. The stimulus imparted to military science by
Napoleon provided a fruitful ground in which ingenious ideas might emerge. With the
development of very heavy artillery, it became desirable to be able to measure the strength of
the horses pulling the gun carriages, and an ingenious rnultipurpose dynamometer was
invented partly for this purpose (Regnier 1798).
These two themes, occurring as they did in the context of the great wave of pure scientific
curiosity that followed Newton, led to the development of scientific dynamometry as one uses it
clinically today. An historical account of the first two all-purpose dynamometers is thus perhaps
of interest to all workers in the neuromuscular disciplines.

It is known that a dynamometer existed before Desaguliers' publication of his own invention in
1763, but no records exist of the exact construction of this earlier model. It was invented by the
master clockmaker, George Graham (1675-1751). Graham was a friend and pupil of Tompion's
and succeeded to his master's business (Bullock's Roll 1720). He invented the mercurial
pendulum and the dead-beat escapement; it was said that his manual dexterity was remarkable,
and "the thoroughness of his work unrivalled". He was a contemporary of Desaguliers, who
gave him credit for the primary invention 'to which I have made some small Additions"
(Desaguliers 1763d). Contemporaries of both these men referred to the modified dynamometer
as the Graham-Desaguliers Instrument.

John Theophilus Desaguliers (1683-1744) was born at La Rochelle, France, but was brought to
England in infancy by his father, a Protestant minister, after the revocation of the Edict of
Nantes in 1685. He became an esteemed scientist, writing extensively on the physical and
mathematical principles of optics, steam engines, electricity and magnetism. He designed an
experiment to compare the Paris and English units of Weights (Desaguliers 1720), and a
machine to ventilate sick rooms (Desaguliers 1735). Desaguliers was one of the first scientists
to give lectures to the general public on science (Major 1962). He had a great flair for making
apparatus and models, and used these extensively to demonstrate the principles of applied
physics. It was perhaps because of this, in conjunction with his great interest in the physics of
human muscle action, that he designed the dynamometer, which bears his name. Feats of
strength had a fascination for him. He describes, before an annotation on Newton's Laws of
Motion, how he went to see "Thomas Topham, born in London and now about 31 years of age
... with Muscles very hard and prominent. Before l give my next Lecture, it may not be improper
to give an account of a Man of very great natural Strength, who lives now here in London, and
shows several surprising Effects of his Strength" (Desaguliers 1763c). On another occasion he
took four students to the "Blue Pots" pub in the "Hay-market" to see a strong man perform. He
illustrated the physical principles of lever systems using human arm and leg muscles (Fig. 1);
his dynamometer was constructed to standardize the mechanical advantage of Agonist and
synergistic muscle groups. Desaguliers was elected a Fellow of the Royal Society in 1744, and
subsequently was awarded the Copley Medal on three separate occasions - a unique


Fig. 1. Desagulier’s illustration (1763) of the different mechanical advantage of the biceps, in different positions of the upper limb. His first
dynamometer was an attempt to standardize the mechanical advantage of the muscle being tested.


The dynamometer is illustrated in Figure 2, which is from Desaguliers' original engraving of
1763. Constructed of wood and iron, it consisted of a supporting frame, a lever system and
adjustable weights. The operating principle was that of a lever of the first order, with the load
moment variable by both adjustable weights and variable moment-arm length. The operator
grasped a fixed static handle with his free hand; the test hand grasped the handle of an Lshaped
lever, which was pulled towards the static hand. The sliding weight was adjusted until
the distal arm of the lever (the "steelyard") could just be lifted. The force exerted by the test arm
was then calculated by noting both the weight applied and its distance from the fulcrum along
the moment-arm. A separate attachment "to test the Strength of the Fingers" was also provided
(Desaguliers 1763d).


Fig. 2. The Graham-Desaguliers dynamometer, invented in 1763.
From Desaguliers' original engraving. This machine tested essentially forearm strength. The static hand grasped the back handle and the test hand, the fore handgrip. Pulling the handgrip lifted the adjustable weight on the lever arm. (Desaguliers 1763 -
Plate 23).

Desaguliers did not record the individual details of his strength-testing experiments, but
summarizes his work in "Now Experience shows us, that in a robust young Man ....... the
combined force of the biceps and brachialis muscles . . . is greater than the Force of 560
Pounds". A summary of the experiments, and their results, is shown in Table 1. He described
the anatomical relationships of muscles and bones (as lever systems) in detail, and by
measuring the strength of a limb in different positions altered the mechanical advantages of
individual muscles in larger muscle groups. This led on to practical considerations of how
various workers carry loads differently - ”a Porter will carry 200 lb, and walk at the rate of three
miles an Hour: A Coal-heaver or Porter that carries Coals, will carry 250 lb, but then he does not
go very far before he lays down his Burthen" (Desaguliers 1763f). Surprisingly, after
demonstrating his dynamometer, he did not publish any systematic results obtained with it. The
machine subsequently caught the interest of Buffon, in Paris, who wanted a dynamometer for
his anthropological studies. Desaguliers' contributions to dynamometry are three-fold: (a) he
established the importance of a standard position when a particular muscle is being tested; (b)
he made quantitative dynamometry practical for the first time; and (c) he established the
variation, from person to person, of the strength of an individual muscle compared with body
stamina as a whole - ". . . all Men are not proportionately strong in every Part, but some are
strongest in the Arms, some in the Legs . . ." (Desaguliers 1763d).

Edme Regnier (1751-1825) was a famous Parisian mechanical engineer, who like Desaguliers
was skilled at inventing mechanical devices. His list of inventions is formidable, ranging from
garden secateurs through the combination lock to devices designed to grade the explosive
power of different samples of gunpowder (Societe de Gens de Lettres et de Savants 1843). He
was in favour with the post-Revolutionary committees that controlled scientific endeavour in the
decade following 1792, and published a considerable number of new inventions and devices.
He received the stamp of approval from the Comite Central de I'Artillerie in 1798 for work on a
new gun-carriage, and before the same influential group demonstrated, in passing, a new
dynamometer which the learned officers pronounced "of ingenious design, mechanically simple,
and easy use" (Comite Central de I'Artillerie 1798). Regnier was awarded the ‘Legion
d'Honneur’ for his inventions and discoveries in 1815.

This ingenious device is shown in Fig. 3, from Regrier's original drawing in 1798. The French
anthropologists Buffon and Gueneau de Montbelliard were very interested in comparative
studies of human strength, essentially between different races. They tried Leroy's dynamometer
but found its application too narrow. (Leroy had demonstrated before the Academie des
Sciences a device to measure the strength of the fingers; this consisted of a metal tube, into
one end of which the fingers thrust a plunger against resistance; a graduated scale indicated the
pressure applied.) They also tried the Graham-Desagutiers machine but found "it was too large
and too heavy to be carried" (Regnier 1798). Buffon then approached Regnier directly for help.
Regnier invented a dynamometer, which worked on the basis of distorting a sprung-steel bar,
which operated a pointer, the movement being magnified, through a lever system. Various
attachments allowing the operator to test hand-grip, thigh muscle strength, and even the
strength of horses pulling horizontally were also devised; Regnier used this latter theme to
justify his experiments at the time, that is the military application, but he became very interested
in all the implications of human dynamometry. Besides its potential use in comparing the
strengths of different races of man, he wrote "are we not able to obtain information no less
important ... relative strength at the different ages of life, and in different states of health?"
(Regnier, 1798). This is almost certainly the first reference to the medical use of dynamometry.

Fig. 3. The Regnier dynamometer, invented in 1798; from Regnier's original engraving, showing the assembled instrument with the base-plate and scales, the lever arm that transmit and
magnify the distortion of the handpiece. A similarity with some clinical dynamometers in contemporary use is apparent.


Regnier described three experiments with his instrument although quantitative records are
available for only one of these. Results are summarized in Table 1. His second experiment was
the first recorded attempt to study muscle strength in disease. "I was able equally with
advantage to assess the effects of electricity on a newly-pa- ralysed woman, by the use of this
dynamometer". Regnier's two significant contributions to neurology were (a) the invention of an
all-purpose portable continuously recording dynamometer, and (b) he introduced the concept of
the mean of the maximum force attainable, as an index of an individual's strength. This method
remains the basic practice by which muscular strength is measured today.


Author Experiment Results
Desaguliers (1763g) "Enquiry of the absolute apparent
Force, which can be exerted by the
two Muscles, the Biceps and
Brachiacus, bending the Cubit when
the whole arm is in a supine and
horizontal situation"
"560 Pound Weight". This
was a theoretical
calculation of the maximum
static force within the
muscle, and did not refer to
the weight lifted.
Desaguliers (1763g) "To find the Force which the said
Muscles exert . . ." (singly); "hence
probably may be singly found the
apparent absolute Forces of the
Biceps Muscle ... and of the
"Biceps: 300 pounds"
"Brachlacus: 260 pounds"
Desaguliers (1 763d) "To try one's Strength by Means of
the Machine" (i.e. the Graham-
Desaguliers dynamometer)
The first description of an
experiment in quantitative
Regnier (1798) "To test the Strength of the arms, or
to describe it better, the force of the
"One is not always able to
judge a man's strength by
that of his hand-grip".
Regnier (1798) "To test the force of the whole body,
especially that of the thigh and trunk
Mean value of the
maximum force was 13
myrigrammes (265

The author thanks Miss Ursula Maunsell of the Royal Society for secretarial assistance.

Bulloch's Roll (1700-1730) Unpublished Roll and Biographical Details of Fellows of the Royal Society by W.             Bulloch, F.R.S.,   The Royal Society, London, Vol. 2, p. 833.
Comit@ Central de I'Artilleric (1798) Expriences faites sur des chariots A frottement, de ]a seconde espke,            souniis A 1'examen du Comit6 Central de I'Artilleric, en vertu de 1'ordre du Ministre de la C; uerre, J. Ecole            Polytech., 2: 173-178.
De la Hire, M. (1699) Exainen de la Force de I'Honiine, pour mouvoir des Fardeatix, tent en levant qu'en portajit        et en tirant,  laquelle est consideree absoluiyient et par comparaison a celle des Ainimaux qui portetit et qui        tirent, contme les Chevauy, Histoire de I'Academie Royale des Sciences, 3rd edition, Martin, Coignard et            Guerin, Paris, pp. 153-162.
Desaguliers, J. T. (1720) An Experiment to compare the Paris Weights as they are now used at Paris, with the          English  Weights, Pltilos. Trans. ray. Soc., 31: 112 (only).
Desagullers, J. T. (1735) An account of an instrument or Machine for changing the Air of the Room of sick                  People in a little Time, by either drawing out the foul Air, or forcing in fresh Air, or doing both Successively,         without opening Doors or  Windows, Plyilos. Tratis. ray. Soc., 39: 41-43.
Desaguliers, J. T. (1763a) A Course of Experimental Philosophy, Vol. 1, 3rd edition, Millar, London, p. 253.
Desaguliers, J. T. (1 763 b) Ibid., p. 265.
Desaguliers, J. T. (1763c) Ibid., p. 288.
Desaguliers, J. T. (1 763d) Ibid., p. 290, 29 1.
Desaguliers, J. T. (1763e) Ibid., Plate 23, Fig. 8, p. 292, and facing p. 302.
Desaguliers, J. T. (1763f) Ibid., p. 256.
Desaguliers, J. T. (1763g) Ibid., p. 159-161.
Graharn, G. (1743) An account of a comparison lately made by some gentlemen of the Royal Society, of the            standard of a  yard, and the several weights lately made for their use, Pltilos. Trans. ray. Soc., 42:541,556.
Major, P. R. (1962) The Physical Researches of J. T. Desaguliers, M.Sc. Thesis in History and Philosophy of         Science,   University of London, p. 206.
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    1800,1801,1802,1083 et 1804, Vol. 1 and 11, avec Atlas (par M. C. A. Lesueur et N. Petit), Imprirnerie Royal,         Paris.
Regnier, Citoyen (Edme) (1798) Description et usage du dynamometre, J. Ecole Polytech., 2: 160-173. Societe      de Gens de Lettres et de Savants (1843) Biographie Universelle (Michaud) Ancienne et Moderne, new edition,      Madame C. Desplaces, Paris, Vol. 35, pp. 344-345.

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