There are three major regions to observe in the chart: Minus, Zero, and Plus.
If physical (A) cycle then people tend to be accident prone.
If emotional (B) cycle then possible emotional outbursts.
If intellectual (C) cycle it isn't as important, by itself, as the other two cycles, but if it coincides with the other two it has a contributory effect.
(B) During the 14 plus days, both men and women are prone to cheerfulness, cooperation, and a positive outlook on life.
(C) During the 16 1/2 plus days of this cycle, a person finds it easier to study, write creatively, understand mathematics or pursue any intellectual efforts.
(B) During the 14 minus days persons are converse to the plus days. Both men and women are conducive to moodiness and negativism.
(C) During the 16 1/2 minus days capacities are lessened. These are days better spent in review or practice.
True triple critical points occur only every 29 years. All true and near true triple points will be indicated by a red circle.
Russian military versions of biorhythm charts also take into account the solar flux and lunar phase on the day of your birth. This PBS Nova program discusses these types of biorhythms briefly. The software used to create the biorhythm chart below does not utilize these parameters. And here's a book about biorhythms you may find interesting.
You can read more about this Biorhythm Charting Service here.