(This is taken from the DC Heroes Magic Sourcebook by Dan Greenberg, with a little Marvel adaptation)
In recent years, popular pseudo-science has evolved the idea that human intellectual, emotional, and physical performance is governed by an enigmatic series of repeating sinusoidal cycles caused by fluctuations in the operation of the autonomic nervous system. Popularly known as biorhythms, these cycles fluctuate between peaks and valleys every 11 to 17 days. When one is riding a biorhythmic peak (Days 11-17 of the cycle), he supposedly performs at the peak of his physical, intellectual, intuitional, or emotional capabilities. One who is resting in a biorhythmic valley (Days 22-33 of the cycle), on the other hand, performs far below his potential.
One's exact position within the biorhythmic cycle is easily determined with the aid of a pocket calculator, using the following four-step procedure. Or you can use the link below.1. Make sure the calculator is set to gradians (generally, this means you should press the button labeled "DRG" one time).2. Figure out the number of days the subject has been alive: 365 x the subject's age + 1 for each Leap Year's Day (February 29) the subject has been alive + 1 for the subject's last birthday + the number of days since the subject's last birthday.3. To calculate one's position on the Physical cycle, divide this figure by 4. To calculate one's position on the Emotional cycle, divide this number by 4.5. To calculate one's position on the Intellectual cycle, divide this figure by 5.4. Calculate the sine of each of the totals you reached in step 3 (on most pocket calculators the button labeled "SIN" calculates the sine). A positive final value represents an up day on the apprpriate cycle. The closer the final value approaches +1, the better (for instance, a final value of .99721 is an extremely good day). A negative final value represents a down day on the cycle. The closer the final value approaches -1, the worse.
Although the sophisticated scientists of the Marvel Universe scoff at the theory of biorhythms, the biorhythmic scales do have an influence on human behavior. But not for any of the reasons proposed by the pseudo-scientists. It just so happens (magic being an art of coincidence) that the intensity of the mana flow through most living things tends to fluctuate in sinusoidal cycles with periods almost identical to those of the biorhythmic scale.In other words, one who rests on a biorhythmic peak is more apt to perform at the peak of his abilities, but only because the increased mana flow is more apt to bring favorable luck and circumstances down upon the subject. During this time all Karma costs are halved for the appropriate abilities. At the same time, one who is resting in a biorhythmic valley is likely to perform below his potential, but only because the restricted mana flow is likely to leave the subject more prone to unforseen disasters and setbacks. During this time all Karma costs are doubled for the arropriate abilities.
Physical cycle- Fighting, Agility, Strength, Endurance FEATs and all powers except those of mental or mystical nature.Intellectual cycle- Reason and Intuition FEATs and all mental powers.Emotional cycle- Psyche FEATs and all mystical powers.*Note: If the Intuitional cycle is used substitute it for the Emotional cycle. Then use the Emotional cycle for all FEATs pertaining to the subject's personal life.
The theory of biorhythms is not the only dubious phenomenon that enjoys a certain validity in th Marvel Universe. Automatic writing, astrology, faith healing, numerology, Tarot, divining, palmistry and others all have a legitimate worth: although like the biorythnic scales, none of these disciplines functions for any of the reasons proposed by its practitioners. Many of the mystcal parlor tricks commonly performed in traveling carnivals and smoky shops originated with the powerful sorcerers of the ancient times, even though the actual knowledge of the arcane arts necessary to implement them has been lost to antiquity. A skilled occultist, however, can often take the observations of a typically unskilled palm reader or numerologist and reinterpret them in a useful light.