CIRCADIAN RHYTHMS IN MALE KARATEKA : A PRELIMINARY STUDY
L'objet de cette étude
scientifique est de mettre en évidence s'il existe une "synchronisation
optimale" des phases d'entraînement avec les rythmes circadiens (journaliers)
des sportifs et plus particulièrement de karatéka. En d'autres termes,
le but est de savoir s'il existe des moments dans la journée où les
sujets observés sont plus perfonants qu'à d'autres. Le protocole scientifique
s'appuit sur la réalisation de série de Oï Tsuki modélisés
en 3D afin de rendre compte du rendement mécanique des techniques.
La température bucale, le rythme cardiaque
agissant en qualité d'indicateurs des rythme circadiens.
Bref, cette
étude préliminaire montre que le milieu de l'après midi est le moment
le plus opportun pour établir une performance (Etude déjà confirmé
dans d'autres sports).
INTRODUCTION
Karate is a Japanese martial art and a competitive
sport performed worldwide. In karate, the successful performances
and influenced
by the individual patterns of several physical (endurance, muscular
strength, neuromuscular co-ordination) and psychological (self-esteem,
concentration) factors. Most biological parameters oscillate
periodically over time, with periods ranging from milliseconds to hours,
days,
years and longer. Physiological and behavioural functions usually
present a daily or circadian rhythmicity (24-h period). In the
current study, the circadian patterns of oral temperature, pulse,
and karate
technical performance were investigated in three karaleka.
METHODOLOGY. During a 24-h period, oral temperature, pulse,
and the repeatability of oi-tsuki (lunge punch) were recorded
in
three male
black-belt karateka (2è Dan) aged 20, 22 and 25 years.
Data were collected every 4 hours (6 time points for each karateka).
The
repeatability of oi-tsuki was quantified by using a standardised
test (Sforza et al., 2001). For each karaleka, 10 consecutive
repetitions
of oi-tsuki were recorded by using an optoelectronic image analyzer
(ELITE - B.T.S., Milan, Italy). This instrument allows the computerized
analysis of fast and complex movements from the 3D coordinates
of body landmarks that are detected by 8 infrared-sensitive cameras
(sampling
rate 100 Hz). The 3D reconstruction of the displacements of 13
selected body-landmarks was performed. For each karateka, the
standard deviation
(SD) of the 3 spatial coordinates was computed for each landmark,
as well as a total SD (6). Data were analysed by the single cosinor
method
for circadian rhythmicity (2) The method approximates the data
with a cosine function, y = M + A cos (tot -Kp) characterised
by:
• Period (T): interval for a complete cycle. In the present study, a
24-h period was considered (circadian rhythms).
• MESOR (M): Midline Estimating Statistic of Rhythms; mid-distance between
maximum and minimum of the cosine function that best approximates
the rhythm.
• Amplitude (A): distance between the MESOR and the maximum of the cosine
function. It can be expressed as a percentage of MESOR.
• Acrophase (cp): daytime of the maximum of the cosine function.
The method also calculates the PR (Percentage Rhythm) representing
the percentage of variation explained by the periodical modification
of the analysed variable. The higher the PR the more significant
the rhythm. Significance was set at 10%.
RESULTS. Significant circadian rhythms were found in two karateka
for oral temperature and pulse. For both athletes and parameters,
the acrophases
were in the middle-afternoon. Variations of the repeatability
of oi-tsuki were observed at different times; nevertheless, karate
performance registered no significant rhythmicity. The results
of the single
cosinor
analysis are listed.
DISCUSSION
Temperature and pulse are currently considered as
markers of circadian rhythmicity. Indeed. karateka CL (who had
no significant
rhythms) developed an influenza the day after completion of the
present investigation. The desynchronization of the circadian rhythm
of temperature
also represents a marker
of the jet lag syndrome (I). In karateka MS and Ml, both temperature
and pulse were in phase, with a common speak in the middle-afternoon
(I, 3). Sport performance is generally influenced by different
physical factors, such as endurance, muscular strength, neuromuscular
co-ordination,
that arc usually in phase with the circadian curve of body temperature
(1, 5). Indeed, all the outdoor world records in middle-distance
running set by British athletes over their golden decade were
achieved in the
evening (5). The circadian rhythms of pulse are highly influenced
by exogenous factors such as sleep, ingestion of food, posture,
and motor
exercise (1). This is relevant to athletes who use pulse rate
at rest as a measure of their progress in fitness and to coaches
who
monitor
the training patterns while observing pulse rate responses (5).
The knowledge of the acrophase of pulse may be of interest in
the choice
of the best time to perform daily training. Nevertheless, not
all performances arc correlated with the circadian rhythms of
body
temperature. In particular,
the athletic performances directly linked with the expression
of a high pattern of "explosive" strength, such as throwing, seem
to be not associated with the body temperature curve (5). These disciplines
may be largely determined by the rhythms in motivation and arousal,
which arc themselves influenced by the sleep-wake cycle. These rhythms
associated with the functions of nerve cells and their neurotransmitters
achieve their peaks a little earlier in the day than those connected
to the body temperature curve. Moreover, the peaks of adrenaline and
noradrenaline are observed earlier in the day than those for metabolism.
It may be of interest that some world records in shot and javelin were
set before noon (5). Indeed, karate may be considered a discipline
in which both individual patterns of "explosive" strength
and motivation play an important rule in the achievement of successful
performances. Furthermore in this martial art, great importance
is given to correct form that represent one of the most important
principles
for the evaluation of the performer (4). The capability of repeating
a standardised technique is currently considered an indicator of
the experience of the performer (6). In two karateka (CL, MS),
the peaks
of the repeatability of oi-tsuki were observed before noon (respectively
at 02:02, and 09:25 hours). Nevertheless, no significant circadian
rhythmicity was found. In karate, oi-tsuki represents one of the
basic movements performed either by experienced karateka or by
the beginners
(4). In black-belt karateka, the administration of a more difficult
test, such as a sequence selected from kata (forms), may influence
the individual patterns of repeatability better than a basic counteroffensive
technique.
CONCLUSIONS
Present results may be a first step in the building
of the chronobiological profile of karateka. Karate antagonistic
events,
such as Continental and World Championships, are commonly
performed worldwide. A proper knowledge of the internal body clock
of
the different components of a team could support the prevention
of
the nuisances
directly connected with jet lag. Furthermore, coaches could
be assisted both in the compilation of training periods
and in the
planing of competitions
in foreign countries. In further investigations, larger groups
of participants could be observed, while performing more
complex sequences of karate
techniques.
REFERENCES
1) Atkinsons G, & Reilly T. Circadian variation in sport performance.
Sports Medicine, 1996, 21 (4), 292-312.
2) Carandente F. Elementi di cronobiologia sperimentale e clinica.
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3) Grassi, G.P., Ferrero M., Morelli A., & Sforza C.
Circadian rhythms in young male orientcers. Scientific Journal
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1994, 10,44-53.
4) Nishiyama H., & Brown R.C. Karate: the art of the
empty-hand fighting. Tokyo: Tuttle, 1996.
5) Reilly T. The human body clock and sport performance. Coaching and
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6) Sforza, C, Turci, M., Grassi, G.P., Fragnito, N., Serrao,
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