PERSONAL HYGIENE—EXERCISE.
=Physiological Considerations.=—In the strict sense of the word,
exercise signifies the performance of its functions by any part of
the body; thus, digestion is exercise of the stomach, respiration is
exercise of the lungs, thinking is an exercise of the brain. But the
term is usually applied chiefly to muscular contraction, and restricted
to contraction of voluntary muscles. Involuntary muscles, which are
concerned in the carrying on of the unconscious organic functions of
life, are not directly controllable, and so their growth and state
of nutrition cannot be regulated. There are two sets of involuntary
muscle, which are of special importance—the heart and the muscles of
respiration. The heart contracts at least sixty times per minute; the
respiratory muscles contract about seventeen times per minute; and this
amount of exercise goes on throughout the whole day. But although we
cannot make our hearts beat quicker by a direct volition, and cannot
breathe more rapidly than usual beyond a few seconds, yet a brisk walk
will cause increased action of the heart and respiratory muscles,
as well as a vigorous contraction of the muscles directly concerned
in walking. Going uphill is a valuable exercise for the heart. The
vermicular contractions of the intestines are to some extent also
increased by voluntary exercise, through the indirect excitation of the
whole system; thus, exercise is an important element in the treatment
of constipation.
The muscles contain about a fourth of the whole blood of the body, and
a very large share of the metabolism (page 4) of the body occurs in
them.
Hence the importance of keeping them in a healthy condition by
exercise. The great danger is of not equilibrating the muscular and
nervous functions. The ideal condition is where neither mental nor
muscular culture is neglected, but both are co-ordinated to the
production of a healthy man.
=Effects of Healthy Exercise.=—1. _The Nutrition of the Muscles_ is
improved. The volume, density, and energy of the muscles are increased.
2. _The action of the lungs is increased._ Dr. E. Smith found that if
the air inspired while lying down be represented by unity, the amount
inspired when erect is 1·33; when walking at the rate of one mile
per hour, 1·9; at four miles per hour, 5; at six miles per hour, 7;
riding on horseback, 4·05; swimming, 4·33. Or, putting it in another
way, under ordinary circumstances a man inspires 480 cubic inches
per minute; if he walks four miles per hour, he inspires 2,400 cubic
inches; if six miles an hour, 3,260 cubic inches.
At the same time the amount of carbonic acid expired is increased.
Its amount bears a nearly constant relation to the amount of muscular
exercise, and consequently the amount of carbonic acid eliminated in
various forms of exercise affords a just estimate of their relative
value. The increased elimination of carbonic acid, the corresponding
increased absorption of oxygen, and the absence of increase of
elimination of urea are shown in the following summary of observations
by Pettenkofer and Voit:—
┌──────────┬─────────────┬───────────────────────────┐
│ │ABSORPTION OF│ ELIMINATION IN GRAMMES OF│
│ │ OXYGEN ├──────────────┬──────┬─────┤
│ │ IN GRAMMES.│CARBONIC ACID.│WATER.│UREA.│
├──────────┼─────────────┼──────────────┼──────┼─────┤
│_Work day_│ 955 │ 1284 │ 2042 │ 37·0│
│_Rest day_│ 709 │ 912 │ 828 │ 37·2│
└──────────┴─────────────┴──────────────┴──────┴─────┘
The above amounts are for the entire day. During actual exercise the
excess of elimination of carbonic acid is much greater. Thus, Dr.
E. Smith experimentally found that if the amount of carbonic acid
eliminated during rest be represented by one, the amount walking at two
miles an hour and carrying 7 lbs = 1·85, the amount walking at three
miles an hour = 2·64.
Alcohol diminishes the excretion of carbonic acid, and should therefore
be avoided during muscular training.
By muscular exercise the size of the lungs is increased, and their
_vital capacity_, that is, the amount of air capable of being expired
after a forced inspiration, is considerably increased. Corresponding
with this increase of vital capacity, exercise, especially that in
which the arm and chest muscles are systematically developed, increases
the size of the chest. A perceptible difference in the circumference of
the chest may be noticed after only a few weeks’ methodical exercise.
3. _The action of the skin is increased._—Sensible perspiration is
commonly induced, but less readily in those habituated to hard work.
Insensible perspiration is always increased.
4. _The temperature of the body_ is not increased, so long as
perspiration occurs. Every muscular contraction involves the production
of heat; but this is counteracted by increased evaporation from the
skin, and by the circulatory current carrying the hotter blood to every
part of the body, and so rapidly equalising its temperature. Chilblains
are due to the defective circulation of the blood, and can in most
cases be cured by active exercise aided by warmer clothing and an
abundant supply of oxidisable food.
5. _The Heart and Blood-vessels._—By exercise the heart’s action is
increased in frequency and force. The pulse usually increases from
ten to thirty beats per minute above the rate while at rest. After
prolonged exercise it may temporarily fall below the normal standard.
6. The _Digestion_ and assimilation of food are aided by exercise,
especially when taken in the open air.
7. _The nervous system_ is improved in nutrition and power by a
moderate amount of exercise. In fact, a certain amount of muscular
exercise is essential for a healthy mind.
8. _The elimination of urea_ is not increased by exercise. Evidently
then it is not the metabolism of the nitrogenous substance of the
muscles which supplies the energy for muscular contraction; but of the
other oxidisable and non-nitrogenous substances (such as glycogen and
sugar) contained in them.
In practice it is found that with exercise more nitrogenous and
non-nitrogenous food are both required.
=Effects of Excessive Exercise.=—After prolonged exertion muscles
become _exhausted_. This is associated with an accumulation in the
muscles of the products of their action (especially sarcolactic acid).
Then rest becomes necessary, in order that the effete products may be
removed, and the nutrition of the muscles restored.
Long-continued over-exertion produces _chronic exhaustion_, which
may, if excessive, cause wasting of muscles. Exhaustion is much more
liable to occur when a small group of muscles are exercised out of
all proportion to others. Thus, in clerks, we have what is known as
the _writer’s_ or _scrivener’s palsy_. The muscles of the hand, and
especially of the thumb, cease to respond to the volition of the
writer, but are seized with spasm every time writing is attempted; and
the muscles of the thumb tend to waste. A similar condition sometimes
arises in violinists, tailors, etc. The practical inference from
these facts is, that one group of muscles should not be exercised
disproportionately to the muscles of the rest of the body, and that
proper intervals of rest should be allowed.
Excessive exercise of the whole muscular system is very apt to harm
those of previously sedentary habits. A walking tour entered on with
more zeal than discretion, and not taken by easy stages for the first
few days, is often productive of more harm than good.
In the intervals of great mental labour, as with students, the amount
of exercise should not be _suddenly_ increased, but should be regular
and moderate in amount.
Competitive exercise should be strictly regulated. The Oxford and
Cambridge crews have been said to acquire heart-disease more commonly
than the average, but this is not correct. Hypertrophy of the heart may
occur as the result of severe exercise, and this within certain limits
is not an abnormal condition. Occasionally dilatation of the heart has
been produced in weakly lads.
=Amount of Exercise Desirable.=—According to Parkes, the average daily
work of a man engaged in manual labour in the open air is equivalent
to the work involved in lifting 250 to 350 tons one foot high; this is
a moderate amount, 400 tons being a heavy day’s work. The amount of
muscular exercise involved in this may be easily known by remembering
that a walk of 20 miles on a level road is equivalent to about 353-2∕3
tons lifted 1 foot; and that a walk of 10 miles while carrying 60 lbs.
is equivalent to 247½ tons lifted 1 foot. (Haughton).
The _amount of work done_ by a healthy adult per diem is stated by
M. Foster to be about 150,000 metre-kilogrammes (_i.e._, 150,000
kilogrammes lifted 1 metre). Metre-kilogrammes can be converted into
foot-pounds by multiplying by 7·233; into foot-tons by multiplying by
·003229; 150,000 metre-kilogrammes therefore equal 484·35 foot-tons.
This is considerably in excess of Parkes’ estimate, but in certain
laborious occupations this high amount is reached.
In addition to this amount of external work, there is the internal
work of the heart, muscles of respiration, digestion, etc. This is
estimated by Parkes at about 260 foot-tons.
The internal and external muscular work of the body together amount to
about 1∕7th to 1∕8th of the total force obtainable from the food.
Every healthy man probably ought to take an amount of exercise
represented by 150 tons raised 1 foot, which is equal to the work
done in walking 8½ to 9 miles on a level road. A certain amount
of this exercise is taken in performing one’s daily work; but apart
from this, out-door exercise should be taken equivalent in amount to a
walk of five or six miles. It is impossible to lay down rules to suit
all cases, but a less amount of exercise than that named is probably
incompatible with perfect health.
=Effects of Deficient Exercise.=—The _muscles_ themselves become
enfeebled and wasted. Some wasting of muscle occurs after a few days’
confinement to bed; and a limb confined in a splint speedily loses
its healthy, rounded contour. _Oxidation processes_ are diminished;
less carbonic acid is eliminated, and it tends to accumulate in the
system, owing to the diminished activity of respiration. In consequence
of the diminished oxidation, the temperature of the body is not well
maintained, and the heat is not uniformly distributed. Cold feet are
a common complaint of those who lead sedentary lives, though seldom
complained of by others.
Along with the other muscles, the _heart_ becomes enfeebled and the
circulation less perfect. _Digestion_ is enfeebled; the appetite is
poor. The _nervous system_ also suffers; nervous irritability is a
common result, while sleeplessness—a thing almost unknown among those
who live by the sweat of their brow—is becoming much more common among
the worried and ill-exercised inhabitants of our towns.
Many diseases are favoured by deficient exercise, and can be averted by
systematic exercises and the concomitant increased supply of pure air.
It is often difficult to appraise the relative merits of exercise and
pure air; but there can be no doubt that both are of extreme importance.
The prevention of consumption, even in those with a strong hereditary
tendency, is greatly helped by systematic exercises, especially those
directed to the expansion of the chest cavity. In cases of consumption
there is commonly a history of deficient exercise or an occupation
involving a cramped position, as well as of living in an impure air.
Various deformities are induced by defective exercise of particular
groups of muscles. Thus drooping shoulders may be caused by
shoulder-straps confining the action of the shoulder-muscles in the
earlier years of life. Stooping is favoured by sitting in cramped
positions in school, and by the use of desks not inclined at the proper
angle. Lateral curvature of the spine is due to weakness of the muscles
of the back, and is best treated in its earlier stages by gymnastic
exercises specially directed to strengthening these muscles. The
tendency to such curvatures is greatly increased in girls by the fact
that their trunks are imprisoned in corsets as if in splints, and so
exercise of the trunk muscles is reduced to a minimum.
=Rules respecting Exercise.= 1. _The clothing during exercise should
not be excessive_, and should not interfere with the free play of
the limbs, nor with full expansion of the chest. Flannel is the best
material to wear next the skin, as it absorbs perspiration without
becoming non-porous.
2. _Avoid chill after exercise._ It is well, if there has been any
perspiration during exercise, to strip and scrub the skin, particularly
about the chest and arm-pits, with a rough towel.
3. _Exercise should be systematic and regular._ It is important to
avoid sudden, violent, and competitive exercise. No severe exercise
ought to be undertaken without a gradual training.
4. _The amount of exercise must be regulated by individual fitness._
A chain is no stronger than its weakest link. The muscles may be
stronger than the heart or lungs, and the latter may be fatally injured
by an amount of exercise which the muscles can well bear. Hence the
importance of ascertaining the condition of the vital organs before
entering on a course of training.
Another important bearing of this rule is in relation to the exercise
of growing boys and girls. When we remember that a boy at school will
sometimes grow six to eight inches in a year, it is evident that much
energy is being expended in this direction, and that _excessive_
gymnastic exercise can only do harm. Between the ages of fifteen and
seventeen there is usually the greatest amount of physical development,
and if there is great muscular strain at this period, growth is
interfered with, and the power of resistance to disease may be
seriously lowered.
5. _Every part of the body ought to be exercised._ This is done
spontaneously by the infant. Every muscle of his body acts in sheer
delight. The evils of exercise confined to particular groups of muscles
have been already described. Lawn tennis is very valuable as affording
exercise for both limb and trunk muscles.
6. _Exercise should not be taken immediately after meals_, as thus
digestion is interfered with.
7. _Exercise should be taken, as far as possible, in the open air._ A
small amount of exercise out of doors is much more invigorating than a
large amount indoors.
=The Forms of Exercise= taken may be divided into recreative and
_educational_, though both of course may be recreative under many
circumstances.
The primarily recreative exercises, such as rowing, cricket, football,
tennis, hockey, will, it may be hoped, be never replaced by educational
gymnastics, though the latter possess a high value. The recreative
influence as well as the influence on the power of self-control of such
games as cricket and football render them of national importance.
Educational gymnastics can be applied to exercise the muscles of
any part of the body, and can be exactly graduated to individual
requirements. Singing, speaking, and reading aloud, are forms of
muscular exercise very much neglected, and they are particularly
important, as the lungs and voice are by these means greatly
strengthened, and rendered much less liable to the inroads of disease.
Professor Haughton has shown that the work done by a man walking on
a level surface at the rate of three miles an hour is equivalent to
raising his own weight, _plus_ the weight he carries through 1∕20 of
the distance walked.
Thus, if W = weight of the man,
W^1 = weight carried by him,
D = distance walked in feet,
C = co-efficient of traction (1∕20, at three miles an hour),
then we obtain by the following formula the amount of work done, the
co-efficient of traction being multiplied by 2,240 (the number of
pounds in a ton) to obtain the result in foot-tons.
(W + W^1) × D/(C × 2,240)
In ascending a height, a man raises his whole weight through the
height ascended.
_A regiment of soldiers marches ten miles, each carrying a weight of
60 lbs. What amount of work is performed by each soldier?_
If we assume the average weight of each soldier to be 150 lbs., and
that the march was at the rate of three miles an hour, then—
(150 + 60) × 10 × 5,280/(20 × 2,240) = 247·5 foot-tons.
In this example it is assumed that the march is on entirely level
ground that all weights are carried in the most convenient manner, and
that the rate of travel is three miles an hour. Velocity is gained at
the expense of carrying power. It has been found that the amount of
work is generally inversely as the square of the velocity. Haughton has
determined from Weber’s calculations the co-efficient of resistance for
three velocities.
┌─────────────────────┬────────────────────────┐
│ VELOCITY. │CO-EFFICIENT OF TRACTION│
│ │ OR RESISTANCE. │
├─────────────────────┼────────────────────────┤
│ 1·818 miles per hour│ 1∕28·27 │
│ │ │
│ 4·353 „ „ │ 1∕13·70 │
│ │ │
│10·577 „ „ │ 1∕7·51 │
└─────────────────────┴────────────────────────┘
Parkes has extended these calculations to show the distance in miles
required to be travelled at various velocities to do work equal to 300
foot-tons, and the time required in each instance.
┌───────────────┬───────────────┬───────────────────┬────────────────┐
│ │ │DISTANCE FOR MEN OF│ TIME REQUIRED │
│ VELOCITY IN │CO-EFFICIENT OF│ 156 LBS. TO EQUAL │ IN HOURS │
│MILES PER HOUR.│ RESISTANCE. │ 300 FOOT-TONS. │ AND MINUTES. │
├───────────────┼───────────────┼───────────────────┼────────────────┤
│ │ │ │ hrs. mins. │
│ 2 │ 1∕26·74 │ 12·2 │ 10 36 │
│ │ │ │ │
│ 3 │ 1∕20·59 │ 16·3 │ 5 24 │
│ │ │ │ │
│ 4 │ 1∕16·74 │ 13·3 │ 3 18 │
│ │ │ │ │
│ 6 │ 1∕12·18 │ 9·6 │ 1 36 │
│ │ │ │ │
│ 8 │ 1∕9·60 │ 7·6 │ 0 57 │
│ │ │ │ │
│ 10 │ 1∕7·89 │ 6·3 │ 0 38 │
└───────────────┴───────────────┴───────────────────┴────────────────┘
The co-efficient 1∕20, corresponds very nearly to 3·1 miles per hour,
and it appears that at this rate of travel the greatest amount of work
can be done with the least expenditure of energy.
_How much work is done by a man weighing 150 lbs. who walks 15 miles up
an incline 1 in 200?_
The number of feet ascended in 15 miles
= 5,280 × 15∕200 = 396.
The amount of work done by the man in raising his own weight 396 feet
high
= 396 × 150∕2,240 = 26·5 foot-tons.
The amount of work done in walking 15 horizontal miles at the rate of 3
miles an hour
= 150 × 15 × 5,280/(20 × 2,240) = 265.2 foot-tons.
Total amount of work done = 265.2 + 26.5
= 291.7 foot-tons.
_Eight palanquin bearers carry an officer weighing 180 lbs. and a
palanquin weighing 250 lbs., a distance of 25 miles. Assuming that
each man weighs 150 lbs., what amount of work was done by each man?
(Parkes.)_
250 + 180 = 430
150 × 8 = 1,200
————-
W + W^1 = 1,630
1,630 × 25 × 5,280/(20 × 2,240) = 4,802·7 foot-tons.
This being the total work done, the work per man = nearly 600.3
foot-tons.
_A hill-coolie weighing 150 lbs. goes 30 miles with an ascent of 5,500
feet in three days, carrying 80 lbs. in weight. What is the work per
day? (Parkes.)_
Work of the ascent = (150 + 80) × 5,500∕2,240 = 564·7 foot-tons.
Work of 30 miles walk = 230 × 30 × 5,280/(20 × 2,240) = 813·2 foot-tons.
Total work = 564·7 + 813·2 = 1,377·9.
Total work per day = 1,377·9∕3 = 459·3 foot-tons.
_Suppose a man weighing 150 lbs. in his clothes, carries a load of
bricks weighing 35 lbs. up a perpendicular ladder 30 feet high, 100
times daily, what amount of work does he do; and what will it equal in
miles walked upon a flat road at the rate of 3 miles an hour?_
((150 + 35) × 30 × 100) / 2,240 = 247·8 foot-tons
(185 × D) / (20 × 2,240) = 247·8.
Therefore D = 60,056 feet
= about 11·4 miles.
_Suppose a man strikes 12,000 strokes in 5 hours with a 14-lb. hammer,
raising it at each stroke 4 feet, how much work does he do? Compare
this with a walk of 15 miles on a level ground at 3 miles an hour, the
weight of the man and what he carries being 180 lbs._
(_a_) 12,000 × 14 × 4 = 672,000 foot-lbs. of work
= 300 foot-tons.
(_b_) (180 × 15 × 5,280) / (20 × 2,240) = 318·2 foot-tons.
The two amounts of work are related as 300: 318·2.