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To: scotty who wrote (618)	5/5/2002 3:07:27 PM
From: Thomas M.	Read Replies (1) \| Respond to of 808

(see bold text) PP 69 : DIURNAL CYCLE PARADOX Lately, after several decades of indecisive debate, research has been renewed regarding the possibility of internal biological rhythms having a significant effect on sporting performance, adaptation to different time zones, the immune response and miscellaneous determinants of fitness and health. In particular, several researchers have proposed that the observation that the human biological day is about 25 hours long and not 24 hours means that athletes regularly have to 'catch up' on a missing hour's sleep and factor in this effect when crossing time zones when competing away from home. Although the 25 hour day is not very well known to the average athlete, it has been known for many thousands of years (as the lunar day) and in more recent scientific times it has been measured by researchers who isolated subjects for several months in underground caves or specially insulated apartments. Records of urinary hormone rhythms, body temperatures, activity and so forth showed that most subjects possess a free-running overall rhythms of longer than 24 hours. Aware that the methods of 'isolation' used in these studies controlled only some of the more obvious possible influences such as light, temperature and seasonal changes, other scientists examined the effects of isolating their subjects from electromagnetic fields or by changing the intensity of light in their subterranean chambers (e.g. Aschoff, Poppel & Weever at Max Planck Inst in Germany). The subjects in electromagnetic isolation displayed a cycle period of 25.26 hours, while those in the unshielded rooms displayed a period of 24.84 hour. When a constant electric field of strength some 1000 times greater than the ambient fields was introduced into the shielded rooms, the cycle duration shortened to 23.5 hours. The length of this cycle also decreased as the intensity of the lighting in the room was increased. Justifiably it must be asked if the 25 hour day measured is more characteristic of the Northern Hemisphere subjects used in most of the studies. How would the results have differed if the subjects had been born and bred in more tropical and sunnier climes? Whatever the relevance of these studies, it is apparent that the 24 hour solar day used to measure our work and training days does not accurately describe our biological timing, which is influenced by changes in light, darkness, electromagnetic fields and other environmental factors. But are we justified in simply deposing the 24 hour solar day and enthroning a 25 hour biological day on the basis of these studies? Most studies have concluded that we have an inherent circadian oscillator system that can be entrained to any cycles between 23 to 28 hours, but not to cycles which fall outside this range. Social cues also can have a significant effect on these cycles. Other scientists have examined the apparent rhythms of REM sleep (paradoxical or dream sleep), slow wave sleep and so forth, sometimes measuring the variations in secretion of growth hormone, melatonin and other hormones. Some of this work has resulted in the use of melatonin supplementation to help travelling athletes accommodate more rapidly to new time zones. More cautious scientists have urged conservatism in the premature use of a hormone whose systemic long-term effects are not yet understood, especially since some subjects find that melatonin can cause prolonged drowsiness and fatigue. It is interesting that the 25 hour daily cycle is not only limited to human mammals, but to many other species. It is possible more interesting that this cycle is close to the lunar cycle, which has led to some scientists (not unscientific astrologers!) examining if our longer rhythm is being electromagnetically entrained by lunar activity and modified by flares in solar activity (which have long been shown to affect growth in plants and major changes in weather). The controversial father of this work was Dr F Brown (Biological Clocks 1962; The Rhythmic Nature of Animals & Plants AMERICAN SCIENTIST XLVII 1959, 2: 164 etc), who concluded that there was also a very strong case for exogenous entrainment of biological activity and not just the primacy of simple deterministic internal clocks. His work and that of others also showed that the 25 hour circadian rhythm sometimes switched to slower or faster rhythms and then returned to their original value. This we may link to the subject of a previous P&P, namely that of the phenomenon of 'Chaos' and partial indeterminacy - and suggest that the 25 hour rhythm needs to be understood in the light of physiological or cosmic 'chaos' before it is applied simplistically and erroneously. After all, other work has shown that blood levels of tryptophan, tyrosine and glycogen seem to follow a 24 hour cycle. Why would some biochemicals follow a 24 hour day and others a 25 hour day? Which ones tend to dominate in sporting and physical activity, if any? Early studies by Halberg et al (Physiologic Twenty-Four Hour Rhythms in MAN'S DEPENDENCE ON THE EARTHLY ATMOSPHERE Macmillan, 1962) found a 24 hour rhythm in the rate at which cells synthesise DNA and RNA, with DNA activity reaching a peak as RNA activity is dropping to its nadir. Later studies have revealed similar patterns. Curiouser and curiouser! Then there is the issue of psychological time versus clock time, which can have a profound effect on performance, as is being revealed by research into the effects of stress into the estimation of time, the immune response, healing rates and so on. One would then have to ask which of a short psychological day or a 25 hour biological day would have more profound implications on sporting performance and training. In this respect, is it the altered perception of time (and endogenous chemical profile) produced by visualisation , meditation or other altered state procedures which modifies performance or is it the direct effect of the procedure concerned? Which is the hen and which is the chicken? After all, the ability to consciously manipulate one's perception of time and events in time can have a major effect in improving performance, especially in events where skill and speed are pre-eminent. For those who are concerned about the validity of the different periodisation models, it is interesting to consider the possible complicating effects that may be introduced into apparently meticulously computed periodisation charts by 25 hour rhythms, environmental modulators and self-induced altered state rhythms (chronically practised by TaiChi and other Eastern masters). sportsci.com