Although as early as 1985, Dr. Capersen, Dr. Powell and Dr. Christenson made the important distinction between the concepts of “Physical Exercise” and “Physical Activity”, it is still very common today to see tremendous confusion between them, using them interchangeably even though they are terms that allude to different concepts.
Physical activity refers to any level of activity above rest and sitting that results from skeletal muscle activation and leads to movement and increased energy expenditure. It is an activity performed spontaneously during our lifetime that represents a significant and major energy expenditure. Physical activity in daily life can be classified into occupational, sports, conditional, domestic or other activities.
Exercise is a subset of physical activity that is planned, structured, repetitive and has as its ultimate or intermediate goal the improvement or maintenance of physical (and I would say psychological as well) fitness. Training or exercise must be defined by a prescribed and adherent dose (i.e., mode, intensity, volume/duration, frequency) of effort or work.
The correct understanding and distinction of these terms is fundamental. But so is the distinction between “sedentary behavior”, “physical inactivity” and what we know as “non-exercise activity thermogenesis” (NEAT) according to Stensel et al (2016) . Sedentary behavior can be defined as “any waking behavior characterized by minimal energy expenditure while sitting or lying down”. The term “inactive” is often used to describe individuals who are engaging in insufficient amounts of moderate- to vigorous-intensity physical activity (i.e., not meeting specific physical activity guidelines). NEAT is the energy expended for everything we do in our daily lives that is not sleeping, eating, or playing sports. It ranges from energy expended walking to work, typing, gardening, agricultural work, etc (Levine 2002).
Likewise, it is also not the same as how this sedentary behavior is distributed throughout the day, as this will greatly condition how this sedentary behavior will influence our health and risk of death.
Perhaps it is NOT enough or not enough to train 50 or 60 minutes a day (physical exercise) and then lie on the couch all day (sedentary) because depending on the frequency, volume and intensity of training (if they are low) you may not reach a minimum of sufficient activity to improve your condition and health (inactive), and the fact of spending many hours sitting will substantially increase the risk of disease and death independently, even if you do physical exercise.
Therefore, increasing your daily activity (physical activity) and reducing the time you are sitting or lying down (sedentary) is crucial for health improvement and disease prevention.
So what do I do if I am an office worker, secretary, IT specialist or any other job where I have to spend hours sitting down?
It’s easy: Do physical exercise, have an active leisure and break the sedentary time every so often (every hour for example) by simply getting up, moving and activating yourself, since breaking that sitting time has been shown to substantially reduce the risk of disease.
There is also an association between low levels of physical activity (and/or high levels of “sedentary behavior”) and the risk of overweight and obesity. The study by Levine et al. (2005) is particularly interesting because they observed much higher levels of NEAT in a group of lean individuals than in a group of obese individuals. This demonstrates the complexity of the problem.
If NEAT is subconsciously reduced in response to an exercise intervention or a dietary prescription, clearly this could reduce or even negate any weight loss that the exercise or nutrition intervention prompted. Following an exercise and/or dietary intervention for fat loss, there may be a series of behavioral compensations that may reduce the expected amount of weight loss following such interventions, The fact that after a time of moderate/severe caloric restriction the intention to engage in physical activity decreases and thus reduce in NEAT making us more and more victims of couch and TV, turns this process into a vicious circle of reducing calories and burning less, which leads to stagnation and failure in the progress of many dietary interventions/calorie restrictions that do not take this fact into account.