Any workout routine has many variables. What are they? This post will cover a general definition of exercise duration, training frequency and training duration.
Exercise Duration
How long it takes you to complete the allotted number if sets for a given workout routine, how long a particular training session lasts, how long it takes you to train a bodypart, and even the length of an entire training program constitute duration.
If you are a beginner, you do not need to pay too much attention to this. Learn proper technique and then you can start manipulating various duration-specific components of you training program.
Training Frequency
If you train your entire body on Tuesday, should you do it again on Wednesday or wait until Thursday? The answer is that your body requires a minimum of about 48 hours to fully recover after exercise – sometimes even more is recommended.
Your body requires rest and nutrients before you can train that same muscle group again. There are some exceptions, but a good rule of thumb is this: If you are sore, you are not ready to train that bodypart again.
If you are a beginner, you do not want to go more than about four days without training the same muscle group again. Training too infrequently results in submaximal gains. The answer, then, is to train every 2-3 days.
Training Duration
Forget those two-hour-plus sessions; very few people can maintain the high level of intensity and mental fortitude of a marathon training session without overdoing it. If you follow the exercises, sets, reps and prescription, you should complete your resistance training in 45-60 minutes.
Measure the quality of your workout by the intensity you create, not the length of time you spend in the gym. [source]