The Foundation of Good Exercise Programs

Top Line

Understanding the basic concepts of exercise prescription will allow you to choose the right program and trainer for your needs.


Why It Matters

Without progressive overload, you may be wasting training sessions and increasing your chance of injury.


Key Takeaways 

  1. SAID Principle – The body will adapt to the specific stress you provide
  2. “Stimulus” refers to a measured amount of stress given to cause a reaction
  3. Progressive overload is the systematic plan to gradually increase the level of stimulus provided by exercise
  4. Progressive overload can be applied to any form of exercise 
  5. Keep it simple and make small changes that gradually increase the difficulty of workouts over time


General fitness and health does not require a complex plan. In fact, keeping it simple will lead to great results. When creating or considering an exercise program, there are fundamental concepts that should always be present. The SAID principle and progressive overload are two of these concepts. They can be applied to any exercise modality, and no program is complete without them. Understanding these foundational ideas will allow you to disseminate the good programs and trainers from the bad.


SAID Principle

The Specific Adaptation to Imposed Demands (SAID) principle states that the body responds to stress based upon the type of stressor presented. There are many different forms of stress including but not limited to physical, psychological, and environmental. The body is in a constant fight to maintain homeostasis (equilibrium), so any stressor that disrupts the body will cause an acute reaction. Then, if the stressor is repeated the body will develop traits to protect itself. 

When applying this concept to exercise, the body will adapt based upon the specific type of physical stressor being implemented. This means that if you consistently expose yourself to a specific form of exercise, for instance, weight training, your body will increase skeletal muscle mass and bone density in response to the stress. In contrast, if you consistently run long distances your body will improve your cardiovascular system to meet the demands. It is important to note that if too much of a given stressor is applied, the body will be unable to adequately respond, ultimately resulting in injury or in extreme cases death. If the stress is not enough to disrupt homeostasis, the body will not be forced to create an adaptation. For example, if you are able to complete a squat with 100 pounds, using only 5 pounds will not stimulate a response by the body. 

In exercise physiology, many refer to this stress as a “stimulus”. A stimulus can be considered “anything that produces a response in an organism” (1). The most common measurements of exercise stimuli include intensity, volume and frequency. Depending on the type of exercise and training goals, a program may manipulate one or all of these variables over time.



Intensity is the amount of energy required to complete a task. It can be measured by weight used, speed of movement, or subjective markers like perceived exertion (a self rating of how difficult a given exercise or workout was on a numbered scale). Over time if you want to progress intensity, you can slowly increase these variables. For example, if you bench press with 95 pounds in your first week then week two you increase the weight to 105 pounds and week three 115 pounds. This trend will not continue forever and you are likely to eventually reach a plateau. When this occurs you can progress a new variable such as frequency, volume, or density. If you are a beginner you should start with low intensities while learning proper techniques, then move into higher intensities as you become proficient.



Frequency is how often a stimulus is presented, and is usually measured in days or sessions. For example, if your goal is to increase the size of your legs and you currently lift legs one day a week, you can progress by lifting legs twice a week. The more intense a workout is, the longer the body will need to adequately recover. If you prefer exercising daily, consider moderately intense workouts. If you can only get to the gym a few times a week, aim for more vigorous exercise. 



Volume is the amount of a stimulus presented in a given workout. This may be quantified as repetitions, sets, and time. To properly progress volume, increase one of these measurements each workout. Rep accumulation is when the weight for a given exercise stays constant but the amount of reps performed each week increases. For example, week one you perform 8 reps of leg press with 100 pounds, then week two you perform 10 reps with 100 pounds. You can continue this progression until you are unable to perform more reps at a given weight, then start back over at a heavier weight.  Set accumulation is a similar concept but instead of increasing reps each week you add a new set. If you perform 3 sets of 3 pull-ups week one, then week two you would attempt 4 sets of 3 reps. Consider your goals when deciding which volume is best. Performing heavier exercises for 1 to 3 reps is focused on strength while lighter weights for 8 to 12 reps is primarily for hypertrophy (increase in muscle size).


Progressive Overload

The most fundamental concept to consider when inspecting an exercise program is progressive overload. Regardless of the exercise modality, it must impose enough stimulus to force the body to adapt. Then, over time your body will become used to that level of stress and require a stronger stimulus, or a completely new one. 

To apply this concept, consider a 10-minute beginner yoga session. If this is your first time doing yoga, the short class with basic movements will be enough to stress your body, but after a few sessions it will begin to feel easy. This means your body has adapted to the stimulus. At this point you must increase the level of stress by either increasing the intensity of the session (more difficult positions) or extending the length of the session. This process is never ending but the law of diminishing returns does apply. A beginner will see major adaptations to small stimuli, while an advanced individual will require large stimuli to see minor changes. The goal is to find the minimum effective amount of volume necessary to create an adaptation. More is not always better. 


Bottom Line

Online programs and trainers are more prevalent than ever. When you are browsing for a new program or trainer, look for these basic concepts throughout the protocol. If you ask a trainer how they plan to implement progressive overload, they should always have an answer. When in doubt keep it simple and make small changes over time that gradually make the workouts harder. As long as you continue to progress these variables, you will keep making progress in the gym. 


Sam Bartlett, MSc





  1. ​​