Christian Agudelo, ACSM - CPT
Typically workout phases last no more than 6 weeks. This is because the body begins to adapt to the current phase it is in and can cause you to plateau. By changing the phase every 6 weeks based on the goals set at the beginning of the program you will be constantly challenging your body in every workout and you will begin to notice the positive changes at the end of each 6 week phase.
Earvin Bahena, NSCA - CSCS
The general rule that we use is to change the workout phases every 6 weeks or so.The reasoning behind our 6 week change is simple, your body adapts to certain movements and speeds of exercise that you do over a period of time. In order to combat this not only do we switch the exercises but the speed of how we do them, the rest and repetition range. By altering these factors, you can continue to challenge your body in ways you hadn’t before.
Spencer O'Neil, NASM- CPT
When it comes to the length of a phase we want to have enough time to master the movements while still challenging the body. By changing the exercises every six weeks it allows us ample time to continuously improve on movement patterns while still allowing enough variance to force the body to adapt.
The workout phases of each program are designed to last 6 weeks because it provides sufficient time to learn new exercises, perform them to the best of your ability in an adequate time frame that promotes growth and prevents diminishing returns. Diminishing returns, meaning your body's motor learning is no longer being challenged. However, by entering into new exercise phases every 6 weeks you are less likely to experience diminishing returns and the phases challenge your body to see how it operates at different intensities whether it is for muscular growth, endurance, power, or stabilization.