Fliess called his 28-day cycle the sensitivity or female cycle, but today this rhythm is more commonly referred to as the EMOTIONAL rhythm or cycle. As with the physical cycle, the emotional cycle has a discharge period and a recharge period. The first fourteen days of the cycle are the plus or discharge days. During these days and individual seems to have more emotional "energy." He/She tends to be more cheerful and optimistic. The second fourteen-day period is the recharge or negative period. It is the time when one is likely to find his/her nerves "on edge." This is the period during which one tends to be more irritable and pessimistic, and one hasn't the emotional "strength" to cope with many ordinary problems.
The INTELLECTUAL, or mental cycle may in many respects be the most subtle of all the three biorhythmic patterns. The full cycle runs for 33 days, and, as with the other cycles, the first half of the cycle is a period of discharge of intellectual energy, and the second half a period of recharge. Most educators have noted that there are definite periods in which students appear to learn quickly, and others during which the learning process appears largely to stop. Later it will restart again quite mysteriously.
Biorhythm authorities advise that whenever possible the second half of the cycle should be used as a time for reviewing previously learned material, in order to fix it in the memory.
The term CRITICAL DAYS sounds ominous, more ominous than it really should. In Japan, where biorhythm theory is increasingly popular, critical days are often called "bad days," a term which is even more ominous and misleading. The critical days are those days in any of the three biorhythmic cycles when the cycle switches from discharge to recharge or vice versa. They are often called zero-energy days, but the term "critical days" is the one most commonly used.
A dictionary definition of "critical" is "full of danger or difficulty." And yet it must be stressed that the critical days are not, in and of themselves, dangerous. Biorhythm theory does not and cannot predict that on a particular critical day something bad will happen.
What biorhythm theory does do, however, is pinpoint those days in which one's energies, be they physical, emotional, or intellectual, are at their weakest and most uncertain. Therefore, one is less likely to be able to cope effectively with whatever difficulties might arise.