Evening star., 1939-01-26
Of Stars, Men
And Atoms
Notebook Of Science Progress
In Field, Laboratory
And Study
By Thomas r. Henry.

When one gets tired from exercise
there is always an increase in the
acidity Of the blood, due to the in
creased production of Tactic acid from
the metabolism Of sugars and starches.
So universal is this condition that it
has been considered, perhaps falsely, as
the cause" of exhaustion.
An entirely different viewpoint is pre-
sented in a report to the American
Chemical Society by DR.. David B. Dill
of the Fatigue Laboratory Of Harvard
University. The Tactic acid, he finds,
is the favorite fuel of the heart which
has been called upon for extra exerion.
AS age advances the capacity to pro-
duce an excess of Tactic acid diminishes
and this. says DR.. Dill, may be one
reason why old men are incapable Of
extreme eXertions-such as engaging in
a prizefight or sprinting 100 yards-al-
though they may be able to play golf
or walk leisurely all day without any
heart damage.
'Lactic acid" he says, sometimes is
spoken of as fatigue substance that
should be eliminated as rapidly as pos
sible, but this is not the sound view.
1t is normal intermediate in the
metabolism of carbohydrate and is avail
able as the fuel preferred by the heart.
The capacity to accumulate Tactic
acid in exercise is lost in old age. A
man of 70 may have one-half the capac-
lty for carrying on work in a steady
state which he had in his prime, but
his capacity for work after the supply
Of free oxygen in his blood is depleted
is almost lost. There are many illus
trations of this. De Mar at 49 ran the
marathon as we'll as at %, but sprinting
for 100 yards would be impossible. Glenn
Cunningham runs the mile at % better
than at %, but who knows a successful
sprinter as old as %"
In this same field of investigation,
DR.. Dill said, workers at the Fatigue
Laboratory have uncovered an important
difference between human beings-the
amount of carbon dioXide normally pres
ent in the arterial blood. Some are
always at the upper limit others always
in the lower limit.
Every one knows" he says, that
state of acidosis is characteristic of the
fatigue OF severe exercise and it is be-
leved by some to characterize the morn
ing after chronic fatigue, and the
fatiClla
and low oxygen. With regard to the
acid base balance in normal men, there
is only one important means of ingress
for acids or alkalies-the gastrointestinal
tract. The ordinary person pays no
attention to the balance between acid
and alkali-forming foods in his diet vet
experimental evidence indicates that
very precise regulation of acids and alka-
lies is maintained by the blood and other
tissues Of the body.
This regulation is effected first of
all by reactions between the excess of
absorbed acid or alkali with body sub
stances, chiefly protein which are capa-
bic OF reacting either as an acid or as
a base, and secondly by adjustment of
breathing and by kidney function. Any
one who wishes proof of the adequacy
OF regulation need only take sodium
bicarborate and study his blood at inter-
walls thereafter. Two or three grams
Will hardly produce measurable effect.
twenty grams may raise the bicar-
Donate content of the blood by one
quarter, but at the same time breathing
jc slowed Hnu-Yo hot
to combined carbon dioxide decreases
only slightly. The kidney begins ex-
cretlng the excess base and in few
hours the normal state is restored.
"As to acid base balance in severe
exercise, the reactions involved in the
transformation of stored chemical energy
to mechanical energy are numerous and
complicated In ordinary activity these
reactions are carried through so smooth
ly that we see little evidence of them
IN the blood except for the greater un-
loading OF oxygen and uptake of carbon
dloxlde. If oxygen can be supplied at
an adequate rate, the non-oxidative re-
actions characteristic of contraction are
reversed by oxidative reactions in recov-
cry. In severe exercise, contraction de-
perds on the same reactions but the
oxidatlve phase cannot keep pace and
exhaustion develops when the reserve of
substances capable of supplying energy
in the absence of free oxygen are used up.
There may be several substances
which increase in concentration within
the cells of contracting muscles under
these conditions. but only two of them
are able to leave the cells and enter
the blood in sufficient amounts to dis
turb the acid base balance. These are
carbon dioXide and Tactic acid'
The reactions depend to some extent
on the climate, DR.. Dill believes. Long
distance races can be run best in cold
weather, whereas sprinters make better
times on hot days. Cold climates, where
Tactic acid is produced more slowly, favor
hard work, he believes, while hot cli-
mates may favor brief spurts of exertion
interspersed with long rests.
There is some evidence, he says, that
various diseases may be influenced great
ly by the climatically induced properties
of the blood. For example, pneumonia
is most apt to occur in late winter and
early spring. Nobody knows exactly why
this should happen. Death rates from
various diseases vary greatly in different
climatic zones-a phenomenon which