Glossary of rhythms
The vocabulary of biorhythms, one term per page: a short definition, how it is calculated, a worked example with real numbers and the questions people ask most.
The three cycles
Biorhythm
A biorhythm is a classic model in which three fixed-length cycles begin on the day you are born: physical at 23 days, emotional at 28, intellectual at 33.
Emotional cycle
The emotional cycle lasts 28 days and is the second of the three biorhythm cycles.
Intellectual cycle
The intellectual cycle is the longest of the three biorhythm cycles: 33 days from birth.
Physical cycle
The physical cycle is the shortest of the three biorhythm cycles: it lasts 23 days and starts on the day of birth.
Phases and points of the cycle
Critical day
A critical day is the day on which a biorhythm cycle crosses the zero line and changes phase: from high to low or from low to high.
Double critical day
A double critical day is a day on which two of the three biorhythm cycles cross zero together.
High phase
The high phase is the first half of every biorhythm cycle, the stretch where the curve sits above the centre line.
Low phase
The low phase is the second half of every biorhythm cycle, when the curve drops below the centre line.