InfoKaraté - Sciences and karate, circadian rhythms in male karateka

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. Milano: II Ponte, 1990.
3) Grassi, G.P., Ferrero M., Morelli A., & Sforza C. Circadian rhythms in young male orientcers. Scientific Journal of Orienteering, 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 Sport Sciences Journal, 1994, 1, 3-7.
6) Sforza, C, Turci, M., Grassi, G.P., Fragnito, N., Serrao, G., & Ferrario, V.F, Repeatability of choku-tsuki and oi-tsuki in Shotokan karate: a 3-dimensional analysis with thirteen black-belt kataeka. Perceptual and Motor Skills, 2001, 92, 1230-1232.