Fitness Q&A by Richard Weil
This is a frequently asked question. Currently, there are no research-based, standardized guidelines to follow, yet it is frequently reported that changing workouts will prevent injuries, and I've heard or read more times than I can remember that if you continue to do the same exercise for long periods of time that your body will eventually hit a plateau and the exercise will stop being effective. There is no evidence to support either claim. It is true that injury can occur as the result of overtraining (for example, 50-plus miles per week of running), but typically, in these cases, it's not repeating the same activity over and over that causes the injury, but rather, (1) a rapid increase in intensity or duration, (2) not enough downtime left for recovery, or (3) simply that the individual pushed beyond the limits of what their body could tolerate muscularly or skeletally. In fact, one could make the opposite argument; that an individual might get injured changing workouts. Consider, for example, someone who has been using the Elliptical machine four times a week for more than a year and then suddenly switches to the treadmill, but pushes too hard because they are fit, and winds up injured because treadmill running is more pounding on the joints than the Elliptical.
As for the body eventually hitting a plateau and fitness decreasing if you continue with the same routine, not only isn't there any research to back up this claim, but biologically it doesn't make sense. That's because your body maintains fitness as long as the stimuli remains consistent. If you consistently run three miles every day at the same pace, then oxygen delivery and all the other physiological mechanisms responsible for fitness necessary to run three miles will remain constant. It is true that in the first few weeks or months of a training program there is a learning curve where the body becomes biomechanically more efficient (for example, the more you practice ice skating the better you get), and when you move efficiently, you burn fewer calories than when you move inefficiently, but eventually you reach a consistent level of biomechanical efficiency and then energy expenditure and heart rate remain the same for the same level of exertion. Take elite marathon runners. They do virtually no other activity to train besides running 60- to 70-plus miles per week and yet you'd be hard pressed to argue that their strength or endurance or performance diminishes over time. To the contrary, elite runners tend to improve performance over time.
In strength training, there is a technique called periodization where three training variables are manipulated: (1) timing (monthly cycles during the year), (2) volume (how many reps and sets you lift), and (3) intensity (how hard or how much weight you lift). An example of a basic periodization model would be to lift lightly with high reps (12-15) for two months to increase your muscular endurance and tone, then transition to higher weight and fewer reps for the next two months to build strength, and then take a month off to recover and let your body grow before beginning a new cycle. Proponents of periodization claim that practicing the model will prevent injury, increase strength, and improve performance. There is some research to support these claims, but it must be stated that improvements will depend on the training status of the individual (untrained individuals gain more strength in a program than trained individuals no matter what type of training), and research shows that strength improves significantly even if the program is nonperiodized. I know individuals who rarely change their workouts but maintain their fitness and remain injury-free. I believe, however, that there is value in the periodization model, and so for those who want to learn more, I recommend either of the following books by Tudor Bompa, Periodization Training for Sports and Periodization: Theory and Methodology of Training. I also recommend a review of periodization in the December 2002 issue of the National Strength and Conditioning Association's publication NSCA's Performance Training Journal at http://www.nsca-lift.org/perform/issues/0109.pdf.
How often should you change your workout? Like I said, there are no firm guidelines, but you could, if you like, change your workout every month and see how that works for you; you could keep doing the same exercises if they work for you; or you could listen to your body and change when your strength or performance decreases, when your physique stops changing in the way that you'd like it to or when you're bored.
Take care. Thank you for your question.
Last Editorial Review: 1/3/2007