Understand your natural cycles to unlock your potential for optimal muscle growth
Biological rhythms, or biorhythms, are cycles in our states of physiological, emotional, or intellectual wellbeing. Literally translated, biorhythm means life flow, which refers to a number of different cycles that affect physiological and behavioural processes. The most obvious manifestation of a human biorhythm is the cycle of sleeping and waking, but virtually all of our functions have their own, less evident rhythms.
Many different frequencies are present in biorhythms, such as the human pulse rate, at around 72 beats per minute on average, and the firing of nerve fibres that control human movement through muscle contraction. These are high frequency rhythms, but there are a number of low frequency rhythms as well. One such rhythm is our 24-hour day-night clock, also known as our biological clock. The setting of the sun – exposure to light and changes in temperature – combined with our hormonally-driven sleep patterns and conditioning, and our level of tiredness is what makes us fall asleep. These factors combine with our internal drive to sleep, which is determined by our biological clock, to determine the timing and structure of our sleep.
According to biorhythm theory, biorhythms are classed into three various types, namely the ultra radian rhythms, which are periods shorter than 20-hours such as your heart beat, the circadian rhythms, which have durations of between 20-28 hours, and the infradian rhythms, which goes beyond 28 hours such as seasonal cycles. These endogenous rhythms predict and prepare our bodies for forthcoming events through the release of specific hormones or physiological changes, for example increased sleepiness in the evening prepares us for sleep and increased deep body temperature in the morning precedes our natural wake-up call. The light-dark cycle is a major determining factor in the control of these rhythms, but when combined with social interactions, mealtimes, exercise, and knowledge of clock time all help to keep us totally synchronised.
Most circadian rhythms are controlled by a centre in the brain, in a pair of tiny structures known as the suprachiasmatic nuclei (SCN). Each SCN is a group of a few thousand nerve cells located in the hypothalamus, just above the optic chiasma (the crossing of the optic nerves). Nerve cells of the SCN fire impulses in extremely regular patterns, like metronomes, and the frequency of the pattern varies with the time of day. Cells of the retina and the pineal gland secrete the hormone melatonin in amounts that also vary with the time of day. This release of melatonin is cyclical, and how we feel and function is largely dependent upon its increase and decrease.
The melatonin is synthesised mostly in the pineal gland under the control of the SCN and is normally made at night. The role of melatonin in humans has a modulatory effect on circadian rhythms and probably serves to reinforce and elicit the physiological and behavioural changes associated with darkness. The production of melatonin is then switched off under the governance of the SCN in response to light, as lowered melatonin causes feelings of alertness and ‘awakeness’. Corticosteroid secretion is also affected by the functioning of the pineal gland. For humans, corticosteroid secretion is at its highest in the morning and lowest in the evening.