The three primary biorhythm cycles are:
Physical: The 23-day physical cycle tracks the man's strength, endurance, powers and state of health.
Emotional: The 28-day emotional cycle tracks the stability and positive energy of your psyche and outlook on life, as well as your capacity to empathize with and build rapport with other people.
Intellectual: The 33-day cycle is representative of man's intellectual dynamics: verbal, mathematical, symbolic, and creative abilities, as well as your capacity to apply reason and analysis to the world around you.
Intuitive: The 38-day cycle was discovered later and can't be considered as a primary one. However it may be useful to know when you can trust your “sixth sense”. The cycle tracks an unconscious perception and instincts.