One of the general principles of exercise is the principle of progression.  I would like to address why this principle is important, especially to those of you who are exercising without guidance from a professional.  

ACE explains the principle of progression: “as the body adapts to the exercise program you must gradually increase the overload to continue to adapt. It is critical that all progressions are gradual and small in nature to prevent over loading the body’s ability to recover.”

Let me address beginners.  Start small!  If it is five minutes of walking and 10 crunches, that is great.  It is important to begin exercising at a slow pace and with just a few exercises to start.  Jumping in and trying to do more activity than your body is prepared for is going to set you up for injury.  It can also be very discouraging when you think you should be able to complete a certain task and your body says otherwise.  Do a little bit every day and allow your body to adjust to the new movement.  It will do so quickly and you will be able to safely do more and harder exercises before you know it.   

Next are people who have exercised in the past and are just starting again after some time off.  If you have taken more than about two weeks off, you need to adjust your training plan.  Give yourself time to get back into the groove.  Now, if your time off has been months or even years, just go ahead and consider yourself a beginner!  Yes, you have muscle memory.  Yes, your body will most likely respond a bit faster than a true beginner.  However, you cannot expect to jump back into your routine from the past.  You body is not ready and you are setting yourself up to suffer an injury. 

Notice the two key words from ACE’s definition:  GRADUAL and SMALL.  No matter what your fitness level, your progressions need to safely and slowly become more challenging.  There are many ways to create progressions within a plan.  It could be more weight (even just 1 – 2 pounds), more repetitions, more sets, less rest between exercises, a longer duration or a higher intensity. 

Since I mentioned injuries, let me give you a little motivation to follow the principle of progression and not start out like a crazed, exercise maniac.  If you do suffer some sort of injury, even if it is as small as a pulled muscle, you will be out of commission for at least a week or two.  If you do something a little more serious, like tear a muscle or tendon or sprain an ankle, or develop tendonitis, you are looking at being out for a range of 4 – 12 weeks!  Not to mention possible surgery and/or physical or occupational therapy.  Who has time for that?  It is much easier to start slowly and gradually build your routine into something more challenging that you can safely enjoy doing.  

Remember, start small and start slow.  You want to be safe and be able to exercise for a lifetime.  

References:
http://www.acefitness.org/pdfs/PFTManualUpdates.pdf