Periodization is the organization and division of a training program into smaller, progressive cycles during a specific period of time. These cycles typically include the micro cycle which usually lasts from 5-7 days, the meso cycle which usually lasts from 2 weeks to a few months and the macro cycle which refers to the overall training period and could last up to a year or two.
The micro cycle consists of multiple training sessions that are strung together and designed with meaning and purpose to help you achieve a specific goal. There are many different types of micro cycles including the introduction, restorative, competitive, and the shock micro cycle. The average micro cycle will range between 1 and 7 days.
The meso cycle is longer in length and is made up of many micro cycles that are designed around one specific purpose. Most training programs use the meso cycle to develop one component of fitness such as strength, power, endurance, agility or speed. There are many types of meso cycles including the introduction, base, competitive and restoration cycles. The average meso cycle will last between 1 and 4 months.
The macro cycle usually refers to the entire length of the periodized exercise program and usually lasts about a year. There are usually always 3 phases to the macro cycle - the preparation, competitive and transition phase. During the preparation phase, the focus is on building up a strong base, during the competitive phase the focus is on hitting your athletic peak and during the transition phase the focus is on rest and recovery.
If you would like read a more detailed description on periodization and the different types of periodized programs then check out Dave Tate's The Periodization Bible; Part 1 and 2 from T-Muscle.