|Hyperthermia in Kendo
text bySAITO Makoto (Senshu University)
Hyperthermia refers to an acute condition resulting from excessive exposure
to heat. There are different categories of hyperthermia such as heat
syncope, heat exhaustion, heat stroke, and heat cramps. Hyperthermia
is an extremely dangerous internal illness which, in serious cases,
can even result in death. Examples of death induced by hyperthermia
can be seen particularly in outdoor sports where players spend many
hours outside practicing under the sun such as baseball, soccer and
track and field. However, it is an unfortunate fact that the highest
instances of hyperthermia seen in indoor sports occur in kendo. There
were five cases of hyperthermia resulting in death among kendo practitioners
between 1975 and 1997. In recent
years, there have been hundreds of cases reported annually concerning
kendo practitioners who have been admitted to hospitals for treatment
of hyperthermia, although fortunately these did not result in death.
Recent Kendo Accidents
In recent years introducing preventative measures for hyperthermia has
clearly become the responsibility of individual instructors. On August
30, 2002, a school teacher in charge of instructing kendo was discharged
from his position as he was deemed gresponsible for not taking adequate
measures to treat a student who had succumbed to hyperthermia during
club training, and died as a result.h When this accident occurred, the
only treatment administered by the instructor was to place the student
under a fan, and an ambulance was not called for another two hours.
It is commonly accepted that harsh training regimes are an integral
characteristic of kendo. That being the case, however, it stands to
reason that adequate risk management should also be considered in the
event of an emergency during training. Unfortunately, even though kendo
has the highest rate of hyperthermia of all indoor sports in Japan and
related information is readily available, in actuality it is rarely
Why hyperthermia easily occurs in kendo
Hyperthermia can be divided into the categories of heat syncope, heat
exhaustion, heat cramps, and heat stroke. There are two
causes for hyperthermia:
(1) An acute increase in body temperature through physical exertion
in a hot environment.
(2) Loss of body fluids and salt through sweat.
There are characteristics of kendo training which accentuate these 2
Characteristics which accentuate the risk of hyperthermia
1) The conscious implementation of special summer training
Firstly, summer training holds a special place in kendo, along with
special winter training. Namely, trainees purposefully train in adverse
conditions not so much to improve technique or stamina, but to strengthen
their spirit or mind. To this purpose, students are often deliberately
denied water for hydration during training. Indeed, it is conceivable
that training in such a harsh environment does contribute to the development
of a resilient mind. On the other hand though, it is also undeniable
that such actions can be life threatening.
2) Keiko-gi (training top) and bogu (protective equipment) which retain
body heat and impede hydration
Next, there is the problem of keiko-gi and bogu. According to one research
report, if gokaku-keiko (sparring) is conducted for 1 hour in an environment
where the temperature is 30 with 70% humidity, the traineefs body weight
may decrease from between 3.0% to 5.6%. This loss in body weight corresponds
to the loss of sweat which means a loss of approximately 1.8 to 3.4
litres of sweat (one or two PET bottles). In another report, an experiment
was conducted in which a subject pedalled a bicycle in hot conditions
wearing full kendo equipment. Compared with a shirt and shorts, it was
found that when the kendo equipment was worn the body temperature was
on average 2 higher (maximum close to 40). Kendo wear and protective
armour is purposefully manufactured thick and durable in order to offer
protection from blows with the shinai (bamboo sword). However, this
is not conducive to release of body heat and therefore is conversely
quite dangerous. Also, as the men (facemask) covers the entire face
this also impedes hydration.
3) Training configuration that inhibits hydration
Lastly, there is the problem of the configuration of training sessions.
Typically a training session will be conducted with trainees lined up
in 2 rows facing their partner. Basic drills are practiced in a logical
regimen of pairs in accordance with the instructorfs commands. During
training sessions, there is no time allotted to remove the men or step
out of the training area. The continual practice of techniques, sparring,
and other training patterns such as kakari-geiko (attack practice) and
so on is considered an integral part of the beauty of kendo, and from
an instructional perspective is very time-effective. However, the downside
of this style of training is that if one person steps out their partner
will also have to cease training. Therefore, it is difficult to drop
out temporarily for a break, meaning little opportunity to hydrate even
when the need is felt. Trainees feel obligated to continue training
even if they are not feeling well, which is a cause of hyperthermia.
The connection between hydration and improved performance
Graph 1 compares the results of an experiment of people participating
in athletic activity where one group hydrated and the other did not.
The graph shows a change in heart rate. When fluids are not taken during
exercise the pulse increases dramatically. Because the amount of blood
in the body decreases (water in the blood is expelled from the body
as sweat making the blood thick), this reduces the bloodfs functional
ability to supply oxygen and nutrients to muscles, hence resulting in
an increased heart rate. Naturally, if oxygen and nutrients are not
being delivered throughout the body, this is going to result in an adverse
effect on overall athletic function and ability, and cognitive judgment
will decrease. In other words, continuing to train without maintaining
fluid intake will adversely affect athletic performance compared to
when fluid intake is maintained. In this sense, fluid intake is not
only necessary to prevent hyperthermia, but is also vital in maintaining
a high level of athletic performance.
What preventative care can be taken? -Suitable environment-
What kind of care can be taken when training in a hot environment? Graph
2 is a guide for preventative measures against hyperthermia. Be sure
to install a thermometer that can read humidity in the dojo. Japanese
summers are extremely humid. Although this information is not included
in the graph, there are some instructional manuals that recommend taking
250cc of water every 15 minutes. Taking this advice into consideration,
it becomes clear how dangerous the conditions of customary kendo training
really are. Furthermore, this information does not take into account
the equipment worn while doing kendo, which means that even more care
needs to be taken.
What kind of fluids should be consumed? |Amount, salt, temperature-
Fluid intake is an effective means of preventing hyperthermia. Drinking
pure water does have some positive effects; however, it can also conversely
be a cause of hyperthermia. For example, if one experiences calf muscle
cramps while practicing in a hot training environment, this may well
be heat cramp, and could be due to a decrease of sodium in the body.
The concentration of sodium in the body decreases because athletes sweat
and only drink water to hydrate. In other words, water intake can give
rise to heat cramps. Although it is better to drink some water than
none at all, in order to prevent hyperthermia it is crucial to include
0.1 to 0.2% salt content (1 to 2 g of salt per 100 ml of water). Sports
drinks are useful because of their sodium content. However, if there
is no time to prepare such beverages before training, it will suffice
to swallow a pinch of salt when drinking water.
Furthermore, the water temperature is also a critical factor in preventing
hyperthermia. Although different books will give differing information,
it is generally accepted that if the water is between 5 and 15 degrees
C, it will facilitate quick travel and absorption in the intestines.
Also, cold water has the effect of cooling the body down from the inside.
Therefore it is advisable to make some cold water available in a hot
Regardless of what measures are taken to prevent hyperthermia, unfortunately
there is always a risk that it will occur in the midst of a gruelling
training session. As I mentioned in the introduction of this paper,
an accident that is not dealt with appropriately will not only be the
responsibility of the instructor, but far more importantly it may result
in the tragic loss of life of a student. Kendo accidents that have the
potential to result in death include shinai breakage, or a blow to the
back of the head after falling over. However, the most representative
examples of death caused through internal injuries stem from hyperthermia,
and measures must be taken to minimalise this possibility.
Measures to be taken against hyperthermia are as follows:
1. Observation: When a student says they are feeling bad, appears to
moving awkwardly, or falls over during training, the instructor should
immediately try to establish symptoms by checking (a) consciousness
(call their name, lightly tap them on the shoulder, and if they are
responsive ask them a question which they should be able to answer easily)
and (b) physical indications (consciousness, breathing, pulse, complexion,
body temperature, and temperature of hands and feet).
2. Treatment: Immediately after observing the above, treatment must
be administered in the following order: (a) Rest (remove bogu and loosen
the ties on the keiko-gi.) (b) Cool down (rest the player in an air-conditioned
room or somewhere with a breeze, but out of the sun). (c) Cool down
2 (massage the whole body with a cold towel and fan them. Apply an icepack
under the armpits and on the thighs). (d) Supply fluids (if the person
is completely conscious). Counter-measures for hyperthermia are introduced
in Kendo Igaku Q&A (Kendo Medicine Q & A) published by the medical
committee of the All Japan Kendo Federation. There are also many books
and manuals which are easily available, including downloadable information
on the homepage of the Japan Sports Association. I recommend that you
read it before we head into the summer season.
Making rules for hydration
Currently it appears that there are few dojos or teams that actively
hydrate during training. In school clubs, junior students are busy preparing
for the next session or looking after their seniors, which leaves little
time to hydrate during breaks. This makes it necessary to implement
rules ensuring that students actively hydrate.
1) Lining up in file
Kendo training sessions are generally conducted with trainees lining
up facing their partners and forming two lines, and then practicing
set techniques in given time frames at the command of the instructor.
Because of this typical training structure, if one student decides to
take a break their partner is also forced to stop training. This makes
it difficult for students to secure time during training to hydrate.
However, this problem can be overcome when there is an odd number of
practitioners. With odd numbers, there will always be one practitioner
left waiting to rotate into the training, which is an opportunity to
hydrate. Usually practitioners use this time to check their shinai and
equipment. If there are 20 to 30 members training at once, such an opportunity
will come once every 15 to 30 minutes. If the number of practitioners
is an even number it can be managed by dividing the group into two groups.
Whatever the case, rules can be put in place by which the player who
is waiting to rotate into the file, or the end pair, are designated
to stop training to hydrate.
Removing the men every time to hydrate in kendo is disruptive and lowers
the efficiency of the training session. In order to reduce time loss,
it is a good idea to drink through straws as they can be inserted through
the grill of the men. If you are able to find drink bottles or cups
with straws already inserted (such as those used in fast food stores)
this will minimalise spillage.
3) Drinking rules
Even if instructors recognise that hydration is necessary to ensure
high quality training sessions, it is often considered unseemly or a
breach of etiquette to stand around drinking in the dojo. To counter
this problem rules can be made in regards to how practitioners should
drink while training. For example, it may me a simple matter of deciding
where practitioners should drink (designating an area outside the dojo);
squatting while drinking; or turning your back to the practicing members
while drinking. Maintaining such etiquette is an important part of kendo
that should always be continued.
The method of training, kendo wear and protective equipment, and training
configuration are all important traditional aspects of kendo that have
been developed over a long history, and as such should not simply be
discarded. However, if deaths occur during training sessions, this will
have an adverse effect on kendo tradition and how it is perceived. The
idea gpersevere in the heat and forge a strong mindh is compatible with
the idea gthe training will yield the best results if measures are included
to counter the effects of the heat to ensure high quality training.h
I hope that we hear no news of accidents occurring in kendo training